[sx126x][sx127x] Stop reading a radio that fails while sends are held back

Also drop a leftover preamble_detect key from a test case.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

CODEOWNERS

@@ -175,11 +175,6 @@ esphome/components/ds2484/* @mrk-its
 esphome/components/ds248x/* @tomwellnitz
 esphome/components/ds3231/* @linkedupbits
 esphome/components/dsmr/* @glmnet @PolarGoose
-esphome/components/duco/* @kokx
-esphome/components/duco/number/* @kokx
-esphome/components/duco/select/* @kokx
-esphome/components/duco/sensor/* @kokx
-esphome/components/duco/text_sensor/* @kokx
 esphome/components/duty_time/* @dudanov
 esphome/components/ecocomfort2/* @gledian
 esphome/components/ee895/* @Stock-M
@@ -192,6 +187,7 @@ esphome/components/ens160_base/* @latonita @vincentscode
 esphome/components/ens160_i2c/* @latonita
 esphome/components/ens160_spi/* @latonita
 esphome/components/ens210/* @itn3rd77
+esphome/components/entity_transport/* @clydebarrow
 esphome/components/epaper_spi/* @esphome/core
 esphome/components/es7210/* @kahrendt
 esphome/components/es7243e/* @kbx81
@@ -379,8 +375,7 @@ esphome/components/m5stack_8angle/* @rnauber
 esphome/components/mapping/* @clydebarrow
 esphome/components/matrix_keypad/* @ssieb
 esphome/components/max17043/* @blacknell
-esphome/components/max17048/* @B48D81EFCC @ryansch
-esphome/components/max170xx/* @ryansch
+esphome/components/max17048/* @B48D81EFCC
 esphome/components/max31865/* @DAVe3283
 esphome/components/max31888/* @JiriPrchal
 esphome/components/max44009/* @berfenger
@@ -635,7 +630,9 @@ esphome/components/sun_gtil2/* @Mat931
 esphome/components/switch/* @esphome/core
 esphome/components/switch/binary_sensor/* @ssieb
 esphome/components/sx126x/* @swoboda1337
+esphome/components/sx126x/packet_interface/* @clydebarrow
 esphome/components/sx127x/* @swoboda1337
+esphome/components/sx127x/packet_interface/* @clydebarrow
 esphome/components/sy6970/* @linkedupbits
 esphome/components/syslog/* @clydebarrow
 esphome/components/systa_bus/* @Mat931
@@ -695,6 +692,7 @@ esphome/components/uart/packet_transport/* @clydebarrow
 esphome/components/uart_mux/* @kbx81
 esphome/components/uart_tcp/* @Bascht74
 esphome/components/udp/* @clydebarrow
+esphome/components/udp/packet_interface/* @clydebarrow
 esphome/components/ufire_ec/* @pvizeli
 esphome/components/ufire_ise/* @pvizeli
 esphome/components/ufm01/* @ljungqvist

esphome/components/ch422g/ch422g.cpp

@@ -1,5 +1,4 @@
 #include "ch422g.h"
-#include "esphome/core/helpers.h"
 #include "esphome/core/log.h"
 
 namespace esphome::ch422g {
@@ -60,7 +59,11 @@ bool CH422GComponent::digital_read(uint8_t pin) {
 }
 
 void CH422GComponent::digital_write(uint8_t pin, bool value) {
-  assign_bits(this->output_bits_, 1 << pin, value);
+  if (value) {
+    this->output_bits_ |= (1 << pin);
+  } else {
+    this->output_bits_ &= ~(1 << pin);
+  }
   this->write_outputs_();
 }
 

esphome/components/ch423/ch423.cpp

@@ -1,5 +1,4 @@
 #include "ch423.h"
-#include "esphome/core/helpers.h"
 #include "esphome/core/log.h"
 #include "esphome/core/progmem.h"
 
@@ -63,7 +62,11 @@ bool CH423Component::digital_read(uint8_t pin) {
 }
 
 void CH423Component::digital_write(uint8_t pin, bool value) {
-  assign_bits(this->output_bits_, 1 << pin, value);
+  if (value) {
+    this->output_bits_ |= (1 << pin);
+  } else {
+    this->output_bits_ &= ~(1 << pin);
+  }
   this->write_outputs_();
 }
 

esphome/components/duco/__init__.py

@@ -1,87 +0,0 @@
-import esphome.codegen as cg
-from esphome.components import time, uart
-import esphome.config_validation as cv
-from esphome.const import CONF_DISCOVERY, CONF_ID, CONF_TIME, CONF_TIME_ID
-from esphome.core import ID
-from esphome.types import ConfigType
-
-CODEOWNERS = ["@kokx"]
-DEPENDENCIES = ["uart"]
-DOMAIN = "duco"
-MULTI_CONF = True
-
-CONF_DISABLE_CRC = "disable_crc"
-CONF_DUCO_ID = "duco_id"
-
-duco_ns = cg.esphome_ns.namespace("duco")
-Duco = duco_ns.class_("Duco", cg.Component, uart.UARTDevice)
-# Base of every class that sends requests through the hub
-DucoDevice = duco_ns.class_(
-    "DucoDevice", cg.PollingComponent, cg.Parented.template(Duco)
-)
-DucoDiscovery = duco_ns.class_("DucoDiscovery", DucoDevice)
-DucoTime = duco_ns.class_("DucoTime", cg.PollingComponent, cg.Parented.template(Duco))
-
-# Entities of the platforms take the hub with this
-DUCO_COMPONENT_SCHEMA = cv.Schema({cv.GenerateID(CONF_DUCO_ID): cv.use_id(Duco)})
-
-DISCOVERY_SCHEMA = cv.Schema({cv.GenerateID(): cv.declare_id(DucoDiscovery)}).extend(
-    cv.COMPONENT_SCHEMA
-)
-
-TIME_SCHEMA = cv.Schema(
-    {
-        cv.GenerateID(): cv.declare_id(DucoTime),
-        cv.GenerateID(CONF_TIME_ID): cv.use_id(time.RealTimeClock),
-    }
-).extend(cv.polling_component_schema("15min"))
-
-CONFIG_SCHEMA = (
-    cv.Schema(
-        {
-            cv.GenerateID(): cv.declare_id(Duco),
-            cv.Optional(CONF_DISABLE_CRC, default=False): cv.boolean,
-            cv.Optional(CONF_DISCOVERY): DISCOVERY_SCHEMA,
-            cv.Optional(CONF_TIME): TIME_SCHEMA,
-        }
-    )
-    .extend(cv.COMPONENT_SCHEMA)
-    .extend(uart.UART_DEVICE_SCHEMA)
-)
-
-FINAL_VALIDATE_SCHEMA = uart.final_validate_device_schema(
-    DOMAIN,
-    baud_rate=57600,
-    require_tx=True,
-    require_rx=True,
-    data_bits=8,
-    parity="NONE",
-    stop_bits=1,
-)
-
-
-_request_device_slot = cg.slot_counter("DUCO_DEVICE_COUNT")
-
-
-async def register_duco_device(var: cg.MockObj, config: ConfigType, hub_id: ID) -> None:
-    """Register a device that sends requests, and give it an open request slot on its hub."""
-    await cg.register_component(var, config)
-    hub = await cg.get_variable(hub_id)
-    await cg.register_parented(var, hub)
-    _request_device_slot(str(hub_id))
-    cg.add(hub.register_device(var))
-
-
-async def to_code(config: ConfigType) -> None:
-    var = await uart.new_uart_component(config)
-    cg.add(var.set_disable_crc(config[CONF_DISABLE_CRC]))
-
-    if (discovery := config.get(CONF_DISCOVERY)) is not None:
-        discovery_var = cg.new_Pvariable(discovery[CONF_ID])
-        await register_duco_device(discovery_var, discovery, config[CONF_ID])
-
-    if (time_config := config.get(CONF_TIME)) is not None:
-        clock = await cg.get_variable(time_config[CONF_TIME_ID])
-        time_var = cg.new_Pvariable(time_config[CONF_ID], clock)
-        await cg.register_component(time_var, time_config)
-        await cg.register_parented(time_var, var)

esphome/components/duco/duco.cpp

@@ -1,273 +0,0 @@
-#include "duco.h"
-
-#include "esphome/core/application.h"
-#include "esphome/core/log.h"
-
-namespace esphome::duco {
-
-ESPHOME_LOG_TAG(TAG, "duco");
-
-static constexpr uint8_t HEADER_START = 0xAA;
-static constexpr uint8_t HEADER_END = 0x55;
-static constexpr uint8_t STUFFING = 0x01;  // follows an 0xAA inside a message, not part of it
-static constexpr uint32_t FRAME_GAP_MS = 50;
-
-static constexpr uint32_t DISCOVERY_START_ID = 0;
-static constexpr uint32_t DISCOVERY_STEP_ID = 1;
-static constexpr uint32_t DISCOVERY_START_MS = 16000;
-static constexpr uint32_t DISCOVERY_STEP_MS = 1600;
-static constexpr uint8_t DISCOVERY_MAX_ATTEMPTS = 3;
-
-void Duco::loop() {
-  const uint32_t now = App.get_loop_component_start_time();
-  // Read first: after a slow loop pass the rest of a message is already waiting, which is not silence
-  this->read_available([this, now](uint8_t byte) {
-    if (this->parse_byte_(byte)) {
-      this->last_byte_ = now;
-    } else {
-      this->reset_frame_();
-    }
-  });
-
-  // The last message of a burst has no header after it, so it ends on silence
-  if (this->rx_size_ != 0 && now - this->last_byte_ > FRAME_GAP_MS) {
-    this->finalize_message_();
-    this->reset_frame_();
-  }
-}
-
-void Duco::reset_frame_() {
-  this->rx_size_ = 0;
-  this->escaped_ = false;
-}
-
-void Duco::close_request(DucoDevice *device) {
-#ifdef DUCO_DEVICE_COUNT
-  for (auto &pending : this->pending_) {
-    if (pending.device == device) {
-      pending.function = 0;
-      pending.missed = false;
-      this->update_warning_();
-      return;
-    }
-  }
-#endif
-}
-
-bool Duco::parse_byte_(uint8_t byte) {
-  const size_t at = this->rx_size_;
-  if (at >= MAX_FRAME_SIZE) {
-    ESP_LOGV(TAG, "Message longer than %u bytes dropped", static_cast<unsigned>(MAX_FRAME_SIZE));
-    return false;
-  }
-  const uint8_t prev = at > 0 ? this->rx_buffer_[at - 1] : 0;
-
-  if (at == 1 && prev == HEADER_START && byte == HEADER_END)
-    return false;  // header of the next message
-
-  if (at >= 2) {
-    const bool escaped = this->escaped_;
-    this->escaped_ = false;
-    if (prev == HEADER_START && !escaped) {
-      if (byte == STUFFING) {
-        this->escaped_ = true;
-        return true;
-      }
-      if (at >= 3 && byte == HEADER_END) {
-        this->rx_size_--;  // drop the 0xAA of the header
-        this->finalize_message_();
-        return false;
-      }
-    }
-  }
-
-  this->rx_buffer_[this->rx_size_++] = byte;
-  return true;
-}
-
-void Duco::finalize_message_() {
-  const uint8_t *raw = this->rx_buffer_.data();
-  // length (function, id and data), function, id, data, CRC low, CRC high
-  if (this->rx_size_ < 5 || raw[0] < 2 || this->rx_size_ < raw[0] + 3u) {
-    ESP_LOGV(TAG, "Malformed message dropped: %u bytes, length byte %u", this->rx_size_, raw[0]);
-    return;
-  }
-  const uint8_t length = raw[0];
-
-  const uint16_t computed_crc = crc16(raw, length + 1);
-  const uint16_t remote_crc = encode_uint16(raw[length + 2], raw[length + 1]);
-  if (computed_crc != remote_crc) {
-    if (!this->disable_crc_) {
-      ESP_LOGV(TAG, "CRC check failed: %04X != %04X", computed_crc, remote_crc);
-      return;
-    }
-    ESP_LOGV(TAG, "CRC check failed, ignored: %04X != %04X", computed_crc, remote_crc);
-  }
-
-#ifdef DUCO_DEVICE_COUNT
-  // The box first acknowledges a request with function + 1, then answers with function + 2
-  const DucoMessage message{raw[2], raw + 3, static_cast<uint8_t>(length - 2)};
-  for (auto &pending : this->pending_) {
-    if (pending.function != 0 && pending.id == message.id && pending.function + 2 == raw[1]) {
-      pending.function = 0;
-      pending.missed = false;
-      this->update_warning_();
-      pending.device->receive_response(message);
-      return;
-    }
-  }
-  // Acknowledgements (odd function codes) are expected and never match
-  if ((raw[1] & 1) == 0) {
-    ESP_LOGV(TAG, "Answer %02X with id %u matches no open request", raw[1], message.id);
-  }
-#endif
-}
-
-#ifdef DUCO_DEVICE_COUNT
-void Duco::update_warning_() {
-  for (const auto &pending : this->pending_) {
-    if (pending.missed) {
-      this->status_set_warning(LOG_STR("No answer from the box"));
-      return;
-    }
-  }
-  this->status_clear_warning();
-}
-#endif
-
-void Duco::dump_config() {
-  ESP_LOGCONFIG(TAG,
-                "Duco:\n"
-                "  CRC Disabled: %s",
-                YESNO(this->disable_crc_));
-}
-
-uint8_t Duco::next_id_() {
-  do {
-    this->last_id_++;
-  } while (this->last_id_ == HEADER_START || this->last_id_ == HEADER_END);
-  return this->last_id_;
-}
-
-void Duco::send(DucoDevice *device, uint8_t function, std::initializer_list<uint8_t> data) {
-  if (data.size() > MAX_REQUEST_DATA) {
-    ESP_LOGE(TAG, "Request of %u bytes is too long", static_cast<unsigned>(data.size()));
-    return;
-  }
-  // Not byte stuffed, as in the author's original and no capture shows a request with 0xAA. An 0xAA followed by any
-  // byte but 0x01 or 0x55 reads the same with or without unstuffing on the box, so only those rare pairs are
-  // unverified.
-  const size_t size = data.size();
-  const uint8_t id = this->next_id_();
-  uint8_t frame[5 + MAX_REQUEST_DATA + 2] = {HEADER_START, HEADER_END, static_cast<uint8_t>(size + 2), function, id};
-  std::copy_n(data.begin(), size, frame + 5);
-  const uint16_t crc = crc16(frame + 2, size + 3);
-  frame[size + 5] = crc & 0xFF;
-  frame[size + 6] = crc >> 8;
-  this->write_array(frame, size + 7);
-  this->flush();
-
-#ifdef DUCO_DEVICE_COUNT
-  for (auto &pending : this->pending_) {
-    if (pending.device == device) {
-      pending.missed = pending.function != 0;
-      if (pending.missed) {
-        ESP_LOGV(TAG, "No answer to request %02X with id %u", pending.function, pending.id);
-        this->update_warning_();
-      }
-      pending.id = id;
-      pending.function = function;
-      break;
-    }
-  }
-#endif
-
-  ESP_LOGV_HEX(TAG, frame + 2, size + 5, sizeof(frame), "Sent %s");
-}
-
-static const LogString *node_type_name(uint8_t type) {
-  switch (type) {
-    case 8:
-      return LOG_STR("UCBAT");
-    case 9:
-      return LOG_STR("UC");
-    case 10:
-      return LOG_STR("UCRH");
-    case 12:
-      return LOG_STR("UCCO2");
-    case 13:
-      return LOG_STR("VLV");
-    case 17:
-      return LOG_STR("BOX");
-    case 18:
-      return LOG_STR("SWITCH");
-    default:
-      return LOG_STR("UNKNOWN");
-  }
-}
-
-void DucoDiscovery::setup() {
-  // Give the box time to start before walking its node addresses
-  this->set_timeout(DISCOVERY_START_ID, DISCOVERY_START_MS, [this]() {
-    this->set_interval(DISCOVERY_STEP_ID, DISCOVERY_STEP_MS, [this]() { this->update(); });
-  });
-}
-
-void DucoDiscovery::update() {
-  if (this->attempts_ == DISCOVERY_MAX_ATTEMPTS) {
-    ESP_LOGV(TAG, "No answer for node %u", this->next_node_);
-    this->next_node_++;
-    this->attempts_ = 0;
-  }
-  if (this->next_node_ >= NODE_COUNT) {
-    this->cancel_interval(DISCOVERY_STEP_ID);
-    this->parent_->close_request(this);
-    return;
-  }
-  // Without an answer by the next step the same node is asked again; a retry is not a missed answer
-  if (this->attempts_ > 0)
-    this->parent_->close_request(this);
-  ESP_LOGV(TAG, "Discovering node %u", this->next_node_);
-  this->attempts_++;
-  this->parent_->send(this, FUNCTION_NODE, {0x01, this->next_node_});
-}
-
-void DucoDiscovery::receive_response(const DucoMessage &message) {
-  // Only the latest attempt is open, so a late answer to an earlier one never arrives here
-  if (message.size >= 1 && this->next_node_ < NODE_COUNT) {
-    if (message.data[0] != 0) {
-      ESP_LOGV(TAG, "Found node %u: type %u", this->next_node_, message.data[0]);
-    }
-    this->node_types_[this->next_node_++] = message.data[0];
-    this->attempts_ = 0;
-  }
-}
-
-void DucoDiscovery::dump_config() {
-  ESP_LOGCONFIG(TAG, "Discovered nodes:");
-  for (uint8_t node = 0; node < NODE_COUNT; node++) {
-    const uint8_t type = this->node_types_[node];
-    if (type != 0) {
-      ESP_LOGCONFIG(TAG, "  Node %u: type %u (%s)", node, type, LOG_STR_ARG(node_type_name(type)));
-    }
-  }
-  if (this->next_node_ < NODE_COUNT) {
-    ESP_LOGCONFIG(TAG, "  Still discovering, at node %u", this->next_node_);
-  }
-}
-
-#ifdef USE_TIME
-void DucoTime::update() {
-  const ESPTime now = this->clock_->now();
-  if (!now.is_valid()) {
-    ESP_LOGV(TAG, "Time is not valid yet");
-    return;
-  }
-  const uint32_t ts = now.timestamp;
-  this->parent_->send(nullptr, FUNCTION_PARAMETER,
-                      {0x05, static_cast<uint8_t>(ts), static_cast<uint8_t>(ts >> 8), static_cast<uint8_t>(ts >> 16),
-                       static_cast<uint8_t>(ts >> 24), 0x00, 0x00, 0x00, 0x00});
-}
-#endif
-
-}  // namespace esphome::duco

esphome/components/duco/duco.h

@@ -1,113 +0,0 @@
-#pragma once
-
-#include <array>
-#include <initializer_list>
-
-#include "esphome/components/uart/uart.h"
-#include "esphome/core/component.h"
-#include "esphome/core/helpers.h"
-
-#ifdef USE_TIME
-#include "esphome/components/time/real_time_clock.h"
-#endif
-
-namespace esphome::duco {
-
-// Function codes of the requests; the box answers a request with function + 2
-static constexpr uint8_t FUNCTION_NODE = 0x0c;       // discovery, status and mode of a node
-static constexpr uint8_t FUNCTION_NODE_DATA = 0x10;  // a block of a node's data (sensors, serial number)
-static constexpr uint8_t FUNCTION_PARAMETER = 0x24;  // read or write a box parameter, set the clock
-
-/// A received message; data points into the receive buffer and is valid only during the callback.
-struct DucoMessage {
-  uint8_t id;
-  const uint8_t *data;
-  uint8_t size;
-};
-
-class DucoDevice;
-
-/// The open request of one device: the answer to it is function + 2 with the same message id.
-struct DucoPendingRequest {
-  DucoDevice *device;
-  uint8_t id;
-  uint8_t function;  // 0 while nothing is open
-  bool missed;       // the request before this one got no answer; sits in padding
-};
-
-class Duco : public uart::UARTDevice, public Component {
- public:
-  void loop() override;
-  void dump_config() override;
-
-  void set_disable_crc(bool disable_crc) { this->disable_crc_ = disable_crc; }
-
-#ifdef DUCO_DEVICE_COUNT
-  void register_device(DucoDevice *device) { this->pending_.push_back({device, 0, 0, false}); }
-#endif
-
-  /// Forget device's open request, for a device that will not send again.
-  void close_request(DucoDevice *device);
-
-  /// Send a request; its answer goes to device, or nowhere if nullptr. A device's new request replaces its
-  /// open one, so an answer is never lost to another device's traffic.
-  void send(DucoDevice *device, uint8_t function, std::initializer_list<uint8_t> data);
-
- protected:
-  // The longest answer to a request sent here is 25 bytes (node status), the longest request 9
-  static constexpr size_t MAX_FRAME_SIZE = 32;
-  static constexpr size_t MAX_REQUEST_DATA = 9;
-
-  bool parse_byte_(uint8_t byte);
-  void reset_frame_();
-#ifdef DUCO_DEVICE_COUNT
-  void update_warning_();  // warn while any device's previous request went unanswered
-#endif
-  void finalize_message_();
-  uint8_t next_id_();
-
-#ifdef DUCO_DEVICE_COUNT
-  StaticVector<DucoPendingRequest, DUCO_DEVICE_COUNT> pending_;
-#endif
-  std::array<uint8_t, MAX_FRAME_SIZE> rx_buffer_{};
-  uint32_t last_byte_{0};
-  uint8_t rx_size_{0};
-  uint8_t last_id_{10};
-  bool escaped_{false};  // the last 0xAA was followed by a stuffing byte, so it starts no header
-  bool disable_crc_{false};
-};
-
-/// Every entity polls the box; deriving from PollingComponent shares its vtable.
-class DucoDevice : public PollingComponent, public Parented<Duco> {
- public:
-  virtual void receive_response(const DucoMessage &message) = 0;
-};
-
-/// Walks the node addresses once after boot; the nodes found are listed in the config dump.
-class DucoDiscovery : public DucoDevice {
- public:
-  void setup() override;
-  void dump_config() override;
-  void update() override;  // one discovery step, run by the step interval
-  void receive_response(const DucoMessage &message) override;
-
- protected:
-  static constexpr uint8_t NODE_COUNT = 0x45;
-
-  std::array<uint8_t, NODE_COUNT> node_types_{};  // 0 when no node answered at that address
-  uint8_t next_node_{0};
-  uint8_t attempts_{0};
-};
-
-#ifdef USE_TIME
-class DucoTime : public PollingComponent, public Parented<Duco> {
- public:
-  explicit DucoTime(time::RealTimeClock *clock) : clock_(clock) {}
-  void update() override;
-
- protected:
-  time::RealTimeClock *clock_;
-};
-#endif
-
-}  // namespace esphome::duco

esphome/components/duco/number/__init__.py

@@ -1,34 +0,0 @@
-from esphome.components import number
-import esphome.config_validation as cv
-from esphome.const import DEVICE_CLASS_TEMPERATURE, UNIT_CELSIUS
-from esphome.types import ConfigType
-
-from .. import (
-    CONF_DUCO_ID,
-    DUCO_COMPONENT_SCHEMA,
-    DucoDevice,
-    duco_ns,
-    register_duco_device,
-)
-
-DEPENDENCIES = ["duco"]
-CODEOWNERS = ["@kokx"]
-
-DucoComfortTemperature = duco_ns.class_(
-    "DucoComfortTemperature", DucoDevice, number.Number
-)
-
-CONFIG_SCHEMA = (
-    number.number_schema(
-        DucoComfortTemperature,
-        unit_of_measurement=UNIT_CELSIUS,
-        device_class=DEVICE_CLASS_TEMPERATURE,
-    )
-    .extend(DUCO_COMPONENT_SCHEMA)
-    .extend(cv.polling_component_schema("60s"))
-)
-
-
-async def to_code(config: ConfigType) -> None:
-    var = await number.new_number(config, min_value=10.0, max_value=25.5, step=0.1)
-    await register_duco_device(var, config, config[CONF_DUCO_ID])

esphome/components/duco/number/number.cpp

@@ -1,26 +0,0 @@
-#include "number.h"
-
-#include <cmath>
-
-namespace esphome::duco {
-
-static constexpr uint8_t PARAMETER_COMFORT_TEMPERATURE = 0x12;
-static constexpr uint8_t GROUP_COMFORT_TEMPERATURE = 0x0a;
-
-void DucoComfortTemperature::update() {
-  this->parent_->send(this, FUNCTION_PARAMETER, {0x00, PARAMETER_COMFORT_TEMPERATURE, GROUP_COMFORT_TEMPERATURE});
-}
-
-void DucoComfortTemperature::receive_response(const DucoMessage &message) {
-  // Reads and writes get the same answer: one byte in tenths of a degree, below 10.0 is invalid
-  if (message.size >= 4 && message.data[3] >= 100)
-    this->publish_state(message.data[3] / 10.0f);
-}
-
-void DucoComfortTemperature::control(float value) {
-  const auto tenths = static_cast<uint8_t>(lroundf(value * 10.0f));
-  this->parent_->send(this, FUNCTION_PARAMETER,
-                      {0x01, PARAMETER_COMFORT_TEMPERATURE, GROUP_COMFORT_TEMPERATURE, tenths, 0x00, 0x00, 0x00});
-}
-
-}  // namespace esphome::duco

esphome/components/duco/number/number.h

@@ -1,18 +0,0 @@
-#pragma once
-
-#include "esphome/components/number/number.h"
-
-#include "../duco.h"
-
-namespace esphome::duco {
-
-class DucoComfortTemperature : public DucoDevice, public number::Number {
- public:
-  void update() override;
-  void receive_response(const DucoMessage &message) override;
-
- protected:
-  void control(float value) override;
-};
-
-}  // namespace esphome::duco

esphome/components/duco/select/__init__.py

@@ -1,45 +0,0 @@
-from esphome.components import select
-import esphome.config_validation as cv
-from esphome.types import ConfigType
-
-from .. import (
-    CONF_DUCO_ID,
-    DUCO_COMPONENT_SCHEMA,
-    DucoDevice,
-    duco_ns,
-    register_duco_device,
-)
-
-DEPENDENCIES = ["duco"]
-CODEOWNERS = ["@kokx"]
-
-# Same order as MODE_CODES in select.cpp
-DUCO_MODE_OPTIONS = [
-    "AUTO",
-    "MAN1",
-    "MAN2",
-    "MAN3",
-    "EMPT",
-    "CNT1",
-    "CNT2",
-    "CNT3",
-    "MAN1x2",
-    "MAN2x2",
-    "MAN3x2",
-    "MAN1x3",
-    "MAN2x3",
-    "MAN3x3",
-]
-
-DucoSelect = duco_ns.class_("DucoSelect", DucoDevice, select.Select)
-
-CONFIG_SCHEMA = (
-    select.select_schema(DucoSelect)
-    .extend(cv.polling_component_schema("3s"))
-    .extend(DUCO_COMPONENT_SCHEMA)
-)
-
-
-async def to_code(config: ConfigType) -> None:
-    var = await select.new_select(config, options=DUCO_MODE_OPTIONS)
-    await register_duco_device(var, config, config[CONF_DUCO_ID])

esphome/components/duco/select/select.cpp

@@ -1,47 +0,0 @@
-#include "select.h"
-
-#include "esphome/core/hal.h"
-#include "esphome/core/log.h"
-
-namespace esphome::duco {
-
-ESPHOME_LOG_TAG(TAG, "duco.select");
-
-// Box code of each option, in the order of DUCO_MODE_OPTIONS in __init__.py
-static constexpr uint8_t MODE_CODES[] PROGMEM = {
-    0x00,  // AUTO
-    0x04,  // MAN1
-    0x05,  // MAN2
-    0x06,  // MAN3
-    0x07,  // EMPT
-    0x08,  // CNT1
-    0x09,  // CNT2
-    0x0a,  // CNT3
-    0x84,  // MAN1x2
-    0x85,  // MAN2x2
-    0x86,  // MAN3x2
-    0xc4,  // MAN1x3
-    0xc5,  // MAN2x3
-    0xc6,  // MAN3x3
-};
-
-void DucoSelect::update() { this->parent_->send(this, FUNCTION_NODE, {0x02, 0x01}); }
-
-void DucoSelect::receive_response(const DucoMessage &message) {
-  if (message.size < 1)
-    return;
-  for (size_t i = 0; i < sizeof(MODE_CODES); i++) {
-    if (progmem_read_byte(&MODE_CODES[i]) == message.data[0]) {
-      this->publish_state(i);
-      return;
-    }
-  }
-  ESP_LOGV(TAG, "Unknown mode %02X", message.data[0]);
-}
-
-void DucoSelect::control(size_t index) {
-  // The next update reads the new mode back
-  this->parent_->send(nullptr, FUNCTION_NODE, {0x04, 0x01, progmem_read_byte(&MODE_CODES[index])});
-}
-
-}  // namespace esphome::duco

esphome/components/duco/select/select.h

@@ -1,18 +0,0 @@
-#pragma once
-
-#include "esphome/components/select/select.h"
-
-#include "../duco.h"
-
-namespace esphome::duco {
-
-class DucoSelect : public DucoDevice, public select::Select {
- public:
-  void update() override;
-  void receive_response(const DucoMessage &message) override;
-
- protected:
-  void control(size_t index) override;
-};
-
-}  // namespace esphome::duco

esphome/components/duco/sensor/__init__.py

@@ -1,156 +0,0 @@
-from esphome.components import sensor
-import esphome.config_validation as cv
-from esphome.const import (
-    CONF_ADDRESS,
-    CONF_CO2,
-    CONF_HUMIDITY,
-    CONF_TEMPERATURE,
-    DEVICE_CLASS_CARBON_DIOXIDE,
-    DEVICE_CLASS_DURATION,
-    DEVICE_CLASS_HUMIDITY,
-    DEVICE_CLASS_TEMPERATURE,
-    STATE_CLASS_MEASUREMENT,
-    UNIT_CELSIUS,
-    UNIT_PARTS_PER_MILLION,
-    UNIT_PERCENT,
-    UNIT_SECOND,
-)
-from esphome.types import ConfigType
-
-from .. import (
-    CONF_DUCO_ID,
-    DUCO_COMPONENT_SCHEMA,
-    DucoDevice,
-    duco_ns,
-    register_duco_device,
-)
-
-DEPENDENCIES = ["duco"]
-CODEOWNERS = ["@kokx"]
-
-UNIT_DAYS = "d"
-
-CONF_BYPASS = "bypass"
-CONF_FILTER_REMAINING = "filter_remaining"
-CONF_FLOW_LEVEL = "flow_level"
-CONF_TEMPERATURE_EHA = "temperature_eha"
-CONF_TEMPERATURE_ETA = "temperature_eta"
-CONF_TEMPERATURE_ODA = "temperature_oda"
-CONF_TEMPERATURE_SUP = "temperature_sup"
-CONF_TIME_REMAINING = "time_remaining"
-
-DucoSensor = duco_ns.class_("DucoSensor", DucoDevice, sensor.Sensor)
-DucoReading = duco_ns.enum("DucoReading", is_class=True)
-
-BOX_NODE = 1
-
-
-def _schema(update_interval: str = "60s", **kwargs) -> cv.Schema:
-    return sensor.sensor_schema(
-        DucoSensor, state_class=STATE_CLASS_MEASUREMENT, **kwargs
-    ).extend(cv.polling_component_schema(update_interval))
-
-
-def _node_schema(**kwargs) -> cv.All:
-    """A list of sensors, one per node address."""
-    return cv.ensure_list(
-        _schema(**kwargs).extend({cv.Required(CONF_ADDRESS): cv.int_range(0, 68)})
-    )
-
-
-_TEMPERATURE = {
-    "unit_of_measurement": UNIT_CELSIUS,
-    "accuracy_decimals": 1,
-    "device_class": DEVICE_CLASS_TEMPERATURE,
-}
-
-# key: (what is read, request argument or None for the node address, schema)
-SENSORS = {
-    CONF_CO2: (
-        DucoReading.DUCO_READING_CO2,
-        None,
-        _node_schema(
-            unit_of_measurement=UNIT_PARTS_PER_MILLION,
-            accuracy_decimals=0,
-            device_class=DEVICE_CLASS_CARBON_DIOXIDE,
-        ),
-    ),
-    CONF_TEMPERATURE: (
-        DucoReading.DUCO_READING_NODE_TEMPERATURE,
-        None,
-        _node_schema(**_TEMPERATURE),
-    ),
-    CONF_HUMIDITY: (
-        DucoReading.DUCO_READING_HUMIDITY,
-        None,
-        _node_schema(
-            unit_of_measurement=UNIT_PERCENT,
-            accuracy_decimals=1,
-            device_class=DEVICE_CLASS_HUMIDITY,
-        ),
-    ),
-    CONF_FILTER_REMAINING: (
-        DucoReading.DUCO_READING_FILTER_REMAINING,
-        0x30,
-        _schema(
-            "1200s",
-            unit_of_measurement=UNIT_DAYS,
-            accuracy_decimals=0,
-            device_class=DEVICE_CLASS_DURATION,
-        ),
-    ),
-    CONF_FLOW_LEVEL: (
-        DucoReading.DUCO_READING_FLOW_LEVEL,
-        BOX_NODE,
-        _schema(unit_of_measurement=UNIT_PERCENT, accuracy_decimals=0),
-    ),
-    CONF_TIME_REMAINING: (
-        DucoReading.DUCO_READING_TIME_REMAINING,
-        BOX_NODE,
-        _schema(
-            unit_of_measurement=UNIT_SECOND,
-            accuracy_decimals=0,
-            device_class=DEVICE_CLASS_DURATION,
-        ),
-    ),
-    CONF_TEMPERATURE_ODA: (
-        DucoReading.DUCO_READING_BOX_TEMPERATURE,
-        0x00,
-        _schema(**_TEMPERATURE),
-    ),
-    CONF_TEMPERATURE_SUP: (
-        DucoReading.DUCO_READING_BOX_TEMPERATURE,
-        0x01,
-        _schema(**_TEMPERATURE),
-    ),
-    CONF_TEMPERATURE_ETA: (
-        DucoReading.DUCO_READING_BOX_TEMPERATURE,
-        0x02,
-        _schema(**_TEMPERATURE),
-    ),
-    CONF_TEMPERATURE_EHA: (
-        DucoReading.DUCO_READING_BOX_TEMPERATURE,
-        0x03,
-        _schema(**_TEMPERATURE),
-    ),
-    CONF_BYPASS: (
-        DucoReading.DUCO_READING_BYPASS,
-        0x10,
-        _schema(unit_of_measurement=UNIT_PERCENT, accuracy_decimals=0),
-    ),
-}
-
-CONFIG_SCHEMA = DUCO_COMPONENT_SCHEMA.extend(
-    {cv.Optional(key): schema for key, (_, _, schema) in SENSORS.items()}
-)
-
-
-async def to_code(config: ConfigType) -> None:
-    for key, (reading, argument, _) in SENSORS.items():
-        if (confs := config.get(key)) is None:
-            continue
-        for conf in confs if isinstance(confs, list) else [confs]:
-            var = await sensor.new_sensor(
-                conf, reading, conf.get(CONF_ADDRESS, argument)
-            )
-            await register_duco_device(var, conf, config[CONF_DUCO_ID])

esphome/components/duco/sensor/sensor.cpp

@@ -1,78 +0,0 @@
-#include "sensor.h"
-
-#include "esphome/core/hal.h"
-#include "esphome/core/log.h"
-
-namespace esphome::duco {
-
-ESPHOME_LOG_TAG(TAG, "duco.sensor");
-
-enum class DucoValueFormat : uint8_t {
-  DUCO_VALUE_FORMAT_UINT8,
-  DUCO_VALUE_FORMAT_UINT16,
-  DUCO_VALUE_FORMAT_INT16,
-};
-
-/// A little endian field at offset in the answer. Values outside [minimum, maximum] are dropped;
-/// the box reports those for sensors that are missing or still starting.
-struct ReadingLayout {
-  uint8_t function;
-  uint8_t offset;
-  DucoValueFormat format;
-  uint8_t divisor;
-  int16_t minimum;
-  uint16_t maximum;
-};
-
-// Indexed by DucoReading
-static constexpr ReadingLayout READINGS[] PROGMEM = {
-    {FUNCTION_NODE_DATA, 4, DucoValueFormat::DUCO_VALUE_FORMAT_UINT16, 1, 300, 10000},  // CO2
-    {FUNCTION_NODE_DATA, 2, DucoValueFormat::DUCO_VALUE_FORMAT_UINT16, 10, 0, 1000},    // node temperature
-    {FUNCTION_NODE_DATA, 6, DucoValueFormat::DUCO_VALUE_FORMAT_UINT16, 100, 0, 10000},  // humidity
-    {FUNCTION_PARAMETER, 3, DucoValueFormat::DUCO_VALUE_FORMAT_UINT8, 1, 0, 255},       // filter remaining
-    {FUNCTION_NODE, 2, DucoValueFormat::DUCO_VALUE_FORMAT_UINT8, 1, 0, 255},            // flow level
-    {FUNCTION_NODE, 12, DucoValueFormat::DUCO_VALUE_FORMAT_UINT16, 1, 0, 65535},        // time remaining
-    {FUNCTION_PARAMETER, 3, DucoValueFormat::DUCO_VALUE_FORMAT_INT16, 10, -999, 1000},  // box temperature
-    {FUNCTION_PARAMETER, 3, DucoValueFormat::DUCO_VALUE_FORMAT_UINT8, 1, 0, 100},       // bypass
-};
-
-static ReadingLayout layout_of(DucoReading reading) {
-  ReadingLayout layout;
-  progmem_memcpy(&layout, &READINGS[static_cast<uint8_t>(reading)], sizeof(layout));
-  return layout;
-}
-
-void DucoSensor::update() {
-  switch (layout_of(this->reading_).function) {
-    case FUNCTION_NODE_DATA:
-      this->parent_->send(this, FUNCTION_NODE_DATA, {0x01, this->argument_, 0x00, 0x49, 0x04});
-      break;
-    case FUNCTION_PARAMETER:
-      this->parent_->send(this, FUNCTION_PARAMETER, {0x00, this->argument_, 0x09});
-      break;
-    case FUNCTION_NODE:
-      this->parent_->send(this, FUNCTION_NODE, {0x02, this->argument_});
-      break;
-  }
-}
-
-void DucoSensor::receive_response(const DucoMessage &message) {
-  const ReadingLayout layout = layout_of(this->reading_);
-  const bool wide = layout.format != DucoValueFormat::DUCO_VALUE_FORMAT_UINT8;
-  if (message.size < layout.offset + (wide ? 2 : 1)) {
-    ESP_LOGV(TAG, "Answer of %u bytes is too short", message.size);
-    return;
-  }
-
-  const uint8_t *field = message.data + layout.offset;
-  int32_t value = field[0];
-  if (layout.format == DucoValueFormat::DUCO_VALUE_FORMAT_UINT16) {
-    value = encode_value_le<uint16_t>(field);
-  } else if (layout.format == DucoValueFormat::DUCO_VALUE_FORMAT_INT16) {
-    value = encode_value_le<int16_t>(field);
-  }
-  if (value >= layout.minimum && value <= layout.maximum)
-    this->publish_state(static_cast<float>(value) / layout.divisor);
-}
-
-}  // namespace esphome::duco

esphome/components/duco/sensor/sensor.h

@@ -1,34 +0,0 @@
-#pragma once
-
-#include "esphome/components/sensor/sensor.h"
-
-#include "../duco.h"
-
-namespace esphome::duco {
-
-/// What a sensor reads; the request and where the value is in the answer are in READINGS in sensor.cpp.
-enum class DucoReading : uint8_t {
-  DUCO_READING_CO2,
-  DUCO_READING_NODE_TEMPERATURE,
-  DUCO_READING_HUMIDITY,
-  DUCO_READING_FILTER_REMAINING,
-  DUCO_READING_FLOW_LEVEL,
-  DUCO_READING_TIME_REMAINING,
-  DUCO_READING_BOX_TEMPERATURE,
-  DUCO_READING_BYPASS,
-};
-
-class DucoSensor : public DucoDevice, public sensor::Sensor {
- public:
-  /// argument is the node address, or the parameter number for a box parameter.
-  DucoSensor(DucoReading reading, uint8_t argument) : reading_(reading), argument_(argument) {}
-
-  void update() override;
-  void receive_response(const DucoMessage &message) override;
-
- protected:
-  DucoReading reading_;
-  uint8_t argument_;
-};
-
-}  // namespace esphome::duco

esphome/components/duco/text_sensor/__init__.py

@@ -1,27 +0,0 @@
-from esphome.components import text_sensor
-import esphome.config_validation as cv
-from esphome.types import ConfigType
-
-from .. import (
-    CONF_DUCO_ID,
-    DUCO_COMPONENT_SCHEMA,
-    DucoDevice,
-    duco_ns,
-    register_duco_device,
-)
-
-DEPENDENCIES = ["duco"]
-CODEOWNERS = ["@kokx"]
-
-DucoSerial = duco_ns.class_("DucoSerial", DucoDevice, text_sensor.TextSensor)
-
-CONFIG_SCHEMA = (
-    text_sensor.text_sensor_schema(DucoSerial)
-    .extend(cv.polling_component_schema("300s"))
-    .extend(DUCO_COMPONENT_SCHEMA)
-)
-
-
-async def to_code(config: ConfigType) -> None:
-    var = await text_sensor.new_text_sensor(config)
-    await register_duco_device(var, config, config[CONF_DUCO_ID])

esphome/components/duco/text_sensor/serial.cpp

@@ -1,17 +0,0 @@
-#include "serial.h"
-
-#include <cstring>
-
-namespace esphome::duco {
-
-void DucoSerial::update() { this->parent_->send(this, FUNCTION_NODE_DATA, {0x01, 0x01, 0x00, 0x1a, 0x10}); }
-
-void DucoSerial::receive_response(const DucoMessage &message) {
-  if (message.size > 2) {
-    // The serial number starts at byte 2 and is padded with zeros
-    const char *serial = reinterpret_cast<const char *>(message.data + 2);
-    this->publish_state(serial, strnlen(serial, message.size - 2));
-  }
-}
-
-}  // namespace esphome::duco

esphome/components/duco/text_sensor/serial.h

@@ -1,15 +0,0 @@
-#pragma once
-
-#include "esphome/components/text_sensor/text_sensor.h"
-
-#include "../duco.h"
-
-namespace esphome::duco {
-
-class DucoSerial : public DucoDevice, public text_sensor::TextSensor {
- public:
-  void update() override;
-  void receive_response(const DucoMessage &message) override;
-};
-
-}  // namespace esphome::duco

esphome/components/entity_transport/__init__.py

@@ -0,0 +1,175 @@
+"""Send sensor and binary sensor states to other devices over a packet interface."""
+
+from collections.abc import Callable
+from typing import Any
+
+import esphome.codegen as cg
+from esphome.components import packet_interface
+from esphome.components.binary_sensor import BinarySensor
+from esphome.components.const import CONF_PROVIDER, CONF_REMOTE_ID
+from esphome.components.packet_interface import (
+    CONF_PACKET_INTERFACE,
+    final_validate_interface,
+    interface_layers,
+)
+from esphome.components.packet_interface.layers import CONF_SESSION
+from esphome.components.sensor import Sensor
+import esphome.config_validation as cv
+from esphome.const import (
+    CONF_BINARY_SENSORS,
+    CONF_ID,
+    CONF_SENSORS,
+    CONF_TIMEOUT,
+    CONF_UPDATE_INTERVAL,
+)
+from esphome.cpp_generator import MockObj, MockObjClass
+from esphome.types import ConfigType
+
+CODEOWNERS = ["@clydebarrow"]
+DEPENDENCIES = ["packet_interface"]
+DOMAIN = "entity_transport"
+MULTI_CONF = True
+
+CONF_BROADCAST_ID = "broadcast_id"
+CONF_ENTITY_TRANSPORT_ID = "entity_transport_id"
+
+entity_transport_ns = cg.esphome_ns.namespace("entity_transport")
+EntityTransport = entity_transport_ns.class_("EntityTransport", cg.Component)
+
+_request_remote_sensor_slot = cg.slot_counter("ENTITY_TRANSPORT_REMOTE_SENSOR_COUNT")
+_request_remote_binary_sensor_slot = cg.slot_counter(
+    "ENTITY_TRANSPORT_REMOTE_BINARY_SENSOR_COUNT"
+)
+
+
+def _advertised_id(conf: ConfigType) -> str:
+    return conf.get(CONF_BROADCAST_ID, conf[CONF_ID].id)
+
+
+def _unique_advertised_ids(entities: list[ConfigType]) -> list[ConfigType]:
+    """A receiver tells entities of one type apart by their advertised ids, so each must be different."""
+    seen: set[str] = set()
+    for index, conf in enumerate(entities):
+        if (advertised := _advertised_id(conf)) in seen:
+            raise cv.Invalid(
+                f"The id '{advertised}' is sent for two entities", path=[index]
+            )
+        seen.add(advertised)
+    return entities
+
+
+def _local_entity(cls: MockObjClass) -> Callable[[Any], Any]:
+    return cv.maybe_simple_value(
+        cv.Schema(
+            {
+                cv.Required(CONF_ID): cv.use_id(cls),
+                cv.Optional(CONF_BROADCAST_ID): cv.All(
+                    cv.validate_id_name, cv.Length(max=255)
+                ),
+            }
+        ),
+        key=CONF_ID,
+    )
+
+
+CONFIG_SCHEMA = cv.Schema(
+    {
+        cv.GenerateID(): cv.declare_id(EntityTransport),
+        cv.Required(CONF_PACKET_INTERFACE): cv.use_id(packet_interface.PacketInterface),
+        # Defaults to a periodic resend unless the interface has session and reliability layers
+        cv.Optional(CONF_UPDATE_INTERVAL): cv.All(
+            cv.update_interval, cv.Range(min=cv.TimePeriod(seconds=1))
+        ),
+        # Remote entities lose their state when none arrives for this long
+        cv.Optional(CONF_TIMEOUT): cv.All(
+            cv.positive_time_period_milliseconds,
+            cv.Range(min=cv.TimePeriod(seconds=1)),
+        ),
+        # Entities are numbered with one byte
+        cv.Optional(CONF_SENSORS): cv.All(
+            cv.ensure_list(_local_entity(Sensor)),
+            cv.Length(max=255),
+            _unique_advertised_ids,
+        ),
+        cv.Optional(CONF_BINARY_SENSORS): cv.All(
+            cv.ensure_list(_local_entity(BinarySensor)),
+            cv.Length(max=255),
+            _unique_advertised_ids,
+        ),
+    }
+).extend(cv.COMPONENT_SCHEMA)
+
+
+def _final_validate(config: ConfigType) -> ConfigType:
+    """With a session layer, which clears the states when the peer is lost, nothing would refresh an unchanged state."""
+    layers = interface_layers(config[CONF_PACKET_INTERFACE])
+    if CONF_TIMEOUT in config and layers is not None and CONF_SESSION in layers:
+        raise cv.Invalid(
+            f"Not allowed with a '{CONF_SESSION}' layer, which already clears the states when the other device "
+            "cannot be reached; unchanged states may never be sent again, so they would time out on a working link",
+            path=[CONF_TIMEOUT],
+        )
+    return config
+
+
+FINAL_VALIDATE_SCHEMA = cv.All(
+    final_validate_interface(CONF_PACKET_INTERFACE), _final_validate
+)
+
+
+def _validate_remote_id(config: ConfigType) -> ConfigType:
+    if CONF_REMOTE_ID not in config and not config[CONF_ID].is_manual:
+        raise cv.Invalid(f"'{CONF_REMOTE_ID}' is required unless '{CONF_ID}' is given")
+    return config
+
+
+def remote_entity_schema(base_schema: cv.Schema) -> cv.Schema:
+    """Schema for an entity whose state comes from another device."""
+    return cv.All(
+        base_schema.extend(
+            {
+                cv.GenerateID(CONF_ENTITY_TRANSPORT_ID): cv.use_id(EntityTransport),
+                cv.Required(CONF_PROVIDER): cv.valid_name,
+                cv.Optional(CONF_REMOTE_ID): cv.All(
+                    cv.string_strict, cv.Length(min=1, max=255)
+                ),
+            }
+        ),
+        _validate_remote_id,
+    )
+
+
+def _remote_id(config: ConfigType) -> str:
+    return config.get(CONF_REMOTE_ID) or config[CONF_ID].id
+
+
+async def register_remote_sensor(config: ConfigType, var: MockObj) -> None:
+    hub = await cg.get_variable(config[CONF_ENTITY_TRANSPORT_ID])
+    _request_remote_sensor_slot(str(hub))
+    cg.add(hub.add_remote_sensor(config[CONF_PROVIDER], _remote_id(config), var))
+
+
+async def register_remote_binary_sensor(config: ConfigType, var: MockObj) -> None:
+    hub = await cg.get_variable(config[CONF_ENTITY_TRANSPORT_ID])
+    _request_remote_binary_sensor_slot(str(hub))
+    cg.add(hub.add_remote_binary_sensor(config[CONF_PROVIDER], _remote_id(config), var))
+
+
+async def to_code(config: ConfigType) -> None:
+    interface = await cg.get_variable(config[CONF_PACKET_INTERFACE])
+    var = cg.new_Pvariable(config[CONF_ID], interface)
+    await cg.register_component(var, config)
+    if (interval := config.get(CONF_UPDATE_INTERVAL)) is not None:
+        cg.add(var.set_update_interval(interval))
+    if (timeout := config.get(CONF_TIMEOUT)) is not None:
+        cg.add(var.set_remote_timeout(timeout))
+    sensors = config.get(CONF_SENSORS, [])
+    binary_sensors = config.get(CONF_BINARY_SENSORS, [])
+    if count := len(sensors) + len(binary_sensors):
+        cg.add(var.set_entity_count(count))
+    for conf in sensors:
+        sensor = await cg.get_variable(conf[CONF_ID])
+        cg.add(var.add_sensor(_advertised_id(conf), sensor))
+    for conf in binary_sensors:
+        sensor = await cg.get_variable(conf[CONF_ID])
+        cg.add(var.add_binary_sensor(_advertised_id(conf), sensor))

esphome/components/entity_transport/binary_sensor.py

@@ -0,0 +1,11 @@
+from esphome.components import binary_sensor
+from esphome.types import ConfigType
+
+from . import register_remote_binary_sensor, remote_entity_schema
+
+CONFIG_SCHEMA = remote_entity_schema(binary_sensor.binary_sensor_schema())
+
+
+async def to_code(config: ConfigType) -> None:
+    var = await binary_sensor.new_binary_sensor(config)
+    await register_remote_binary_sensor(config, var)

esphome/components/entity_transport/entity_transport.cpp

@@ -0,0 +1,683 @@
+#include "entity_transport.h"
+#include <algorithm>
+#include <cmath>
+#include <cstring>
+#include "esphome/core/application.h"
+#include "esphome/core/log.h"
+
+namespace esphome::entity_transport {
+
+using packet_interface::PacketBuffer;
+using packet_interface::PacketMetaData;
+
+ESPHOME_LOG_TAG(TAG, "entity_transport");
+
+// The packet type byte holds the format version in its high nibble
+static constexpr uint8_t FORMAT_VERSION = 1;
+static constexpr uint8_t PACKET_DICTIONARY = 0x11;
+static constexpr uint8_t PACKET_DATA = 0x12;
+static constexpr uint8_t PACKET_REQUEST = 0x13;
+// Entity types, in dictionary sections and data records; 0 is not used
+static constexpr uint8_t TYPE_SENSOR = 1;
+static constexpr uint8_t TYPE_BINARY_SENSOR = 2;
+static constexpr uint8_t MAX_TYPE = 31;
+// Packet type and dictionary id
+static constexpr size_t HEADER_SIZE = 5;
+// A dictionary packet's part byte follows the header: the part's index in bits 0-6, and on the last part, bit 7
+static constexpr uint8_t PART_INDEX_MASK = 0x7F;
+static constexpr uint8_t PART_LAST = 0x80;
+static constexpr uint8_t PART_NONE = 0xFF;  // no dictionary is being received in order
+// A data record starts with a 16-bit tag: the entity's number in bits 0-7, its type in bits 8-12, the payload form in
+// bits 13-14, and with PAYLOAD_NONE, the state in bit 15. Any record can be skipped without knowing its type.
+static constexpr size_t TAG_SIZE = 2;
+static constexpr uint8_t TAG_TYPE_SHIFT = 8;
+static constexpr uint8_t TAG_PAYLOAD_SHIFT = 13;
+static constexpr uint16_t TAG_VALUE_BIT = 0x8000;
+static constexpr uint8_t PAYLOAD_NONE = 0;      // the state is in the tag's value bit
+static constexpr uint8_t PAYLOAD_WORD = 1;      // 4 bytes follow
+static constexpr uint8_t PAYLOAD_LENGTH = 2;    // a length byte follows, then that many bytes
+static constexpr uint8_t PAYLOAD_NO_STATE = 3;  // the entity has no state
+static constexpr size_t WORD_SIZE = 4;
+static constexpr size_t MAX_RECORD_SIZE = TAG_SIZE + WORD_SIZE;
+// A dictionary section starts with the entity type, first number and count
+static constexpr size_t SECTION_HEADER_SIZE = 3;
+static constexpr size_t MAX_STRING_LENGTH = 255;
+static constexpr uint32_t DEFAULT_UPDATE_INTERVAL_MS = 15000;
+static constexpr uint32_t REQUEST_INTERVAL_MS = 5000;
+static constexpr uint32_t RETRY_DELAY_MS = 1000;
+static constexpr uint32_t RETRY_TIMER_ID = 0;
+static constexpr uint32_t TIMEOUT_CHECK_INTERVAL_MS = 1000;
+static constexpr uint32_t WARNING_INTERVAL_MS = 60000;
+// How long the interface may refuse every packet before it is reported
+static constexpr uint32_t REFUSED_WARNING_MS = 60000;
+
+static void put_uint32(uint8_t *buf, uint32_t value) {
+  for (size_t i = 0; i != 4; i++)
+    buf[i] = value >> (i * 8);
+}
+
+// True if the NUL terminated str is the same as the len bytes at data
+static bool matches(const char *str, const char *data, size_t len) {
+  return strlen(str) == len && memcmp(str, data, len) == 0;
+}
+
+struct Record {
+  uint8_t number;
+  uint8_t type;
+  uint8_t payload;
+  bool value;
+  const uint8_t *data;  // what follows the tag
+};
+
+static Record parse_record(std::span<const uint8_t> packet, size_t pos) {
+  uint16_t tag = encode_uint16(packet[pos + 1], packet[pos]);
+  return {static_cast<uint8_t>(tag), static_cast<uint8_t>((tag >> TAG_TYPE_SHIFT) & MAX_TYPE),
+          static_cast<uint8_t>((tag >> TAG_PAYLOAD_SHIFT) & 3), (tag & TAG_VALUE_BIT) != 0,
+          packet.data() + pos + TAG_SIZE};
+}
+
+// The size of the data record at pos, or 0 if it does not fit in the packet
+static size_t record_size(std::span<const uint8_t> packet, size_t pos) {
+  if (pos + TAG_SIZE > packet.size())
+    return 0;
+  size_t size = TAG_SIZE;
+  uint8_t payload = parse_record(packet, pos).payload;
+  if (payload == PAYLOAD_WORD) {
+    size += WORD_SIZE;
+  } else if (payload == PAYLOAD_LENGTH) {
+    if (pos + TAG_SIZE == packet.size())
+      return 0;
+    size += 1 + packet[pos + TAG_SIZE];
+  }
+  return pos + size <= packet.size() ? size : 0;
+}
+
+// Checks every record of a data packet, so that a damaged or forged packet changes no state at all
+static bool data_well_formed(std::span<const uint8_t> packet) {
+  for (size_t pos = HEADER_SIZE; pos != packet.size();) {
+    size_t size = record_size(packet, pos);
+    if (size == 0)
+      return false;
+    Record record = parse_record(packet, pos);
+    if (record.type == 0 || (record.value && record.payload != PAYLOAD_NONE))
+      return false;
+    // Types this device knows must use their own payload form; others are skipped
+    if (record.type == TYPE_SENSOR && record.payload != PAYLOAD_WORD && record.payload != PAYLOAD_NO_STATE)
+      return false;
+    if (record.type == TYPE_BINARY_SENSOR && record.payload != PAYLOAD_NONE && record.payload != PAYLOAD_NO_STATE)
+      return false;
+    pos += size;
+  }
+  return true;
+}
+
+// Checks the device name and every section of a dictionary packet before anything is learnt from it
+static bool dictionary_well_formed(std::span<const uint8_t> packet) {
+  size_t pos = HEADER_SIZE + 1;
+  if (pos >= packet.size())
+    return false;
+  pos += 1 + packet[pos];
+  if (pos > packet.size())
+    return false;
+  while (pos != packet.size()) {
+    if (pos + SECTION_HEADER_SIZE > packet.size())
+      return false;
+    uint8_t type = packet[pos];
+    size_t first = packet[pos + 1];
+    size_t count = packet[pos + 2];
+    pos += SECTION_HEADER_SIZE;
+    // Numbers are one byte, and a data record can name types up to MAX_TYPE only
+    if (type == 0 || type > MAX_TYPE || count == 0 || first + count > 256)
+      return false;
+    for (size_t i = 0; i != count; i++) {
+      if (pos == packet.size())
+        return false;
+      pos += 1 + packet[pos];
+      if (pos > packet.size())
+        return false;
+    }
+  }
+  return true;
+}
+
+void EntityTransport::setup() {
+  this->interface_ = this->interface_->top();
+  this->max_packet_size_ = this->interface_->get_max_packet_size();
+  const auto &name = App.get_name();
+  size_t longest_id = 0;
+  for (const auto &entity : this->entities_)
+    longest_id = std::max(longest_id, strlen(entity.id));
+  // A dictionary packet must hold the device name and any one id, which also leaves room for a data record
+  if (name.size() > MAX_STRING_LENGTH || longest_id > MAX_STRING_LENGTH ||
+      HEADER_SIZE + 2 + name.size() + SECTION_HEADER_SIZE + 1 + longest_id > this->max_packet_size_) {
+    this->mark_failed(LOG_STR("max_packet_size too small for the device name and entity ids"));
+    return;
+  }
+  RAMAllocator<uint8_t> allocator;
+  this->buffer_ = allocator.allocate(this->max_packet_size_);
+  if (this->buffer_ == nullptr) {
+    this->mark_failed(LOG_STR("Not enough memory for the packet buffer"));
+    return;
+  }
+  // The dictionary id changes when the device name or any entity changes
+  uint32_t hash = fnv1a_hash(name.c_str());
+  for (const auto &entity : this->entities_) {
+    hash = fnv1a_hash_extend(hash, entity.is_sensor ? TYPE_SENSOR : TYPE_BINARY_SENSOR);
+    hash = fnv1a_hash_extend(hash, entity.id);
+  }
+  this->dictionary_id_ = hash;
+
+  // [&entity] is safe: FixedVector never reallocates, and the parent pointer keeps the capture to one pointer
+  for (auto &entity : this->entities_) {
+#ifdef USE_SENSOR
+    if (entity.is_sensor) {
+      static_cast<sensor::Sensor *>(entity.entity)->add_on_state_callback([&entity](float) {
+        entity.parent->mark_updated_(entity);
+      });
+    }
+#endif
+#ifdef USE_BINARY_SENSOR
+    if (!entity.is_sensor) {
+      // The full state callback also fires for the first state
+      static_cast<binary_sensor::BinarySensor *>(entity.entity)
+          ->add_full_state_callback(
+              [&entity](optional<bool>, optional<bool>) { entity.parent->mark_updated_(entity); });
+    }
+#endif
+  }
+  this->interface_->add_packet_interface_listener(
+      [this](const PacketBuffer &data, const PacketMetaData &) { this->receive_(data); });
+
+  bool session = this->interface_->has_capability(packet_interface::CAPABILITY_SESSION);
+  if (session)
+    this->interface_->add_on_session_state_callback([this](bool connected) { this->on_session_(connected); });
+  // Without a session and reliable delivery, a lost dictionary or state is only replaced by a periodic resend
+  if (this->update_interval_ms_ == 0) {
+    this->update_interval_ms_ = session && this->interface_->has_capability(packet_interface::CAPABILITY_RELIABILITY)
+                                    ? SCHEDULER_DONT_RUN
+                                    : DEFAULT_UPDATE_INTERVAL_MS;
+  }
+  if (this->update_interval_ms_ != SCHEDULER_DONT_RUN)
+    this->set_interval(this->update_interval_ms_, [this] { this->send_all_(); });
+  if (this->remote_timeout_ms_ != 0)
+    this->set_interval(TIMEOUT_CHECK_INTERVAL_MS, [this] { this->clear_remote_states_(true); });
+  this->send_all_();
+}
+
+void EntityTransport::dump_config() {
+  ESP_LOGCONFIG(TAG,
+                "Entity Transport:\n"
+                "  Packet Interface: %s\n"
+                "  Max Packet Size: %zu\n"
+                "  Encryption: %s\n"
+                "  Reliability: %s\n"
+                "  Session: %s\n"
+                "  Dictionary ID: %08" PRIX32,
+                this->interface_->get_name(), this->max_packet_size_,
+                YESNO(this->interface_->has_capability(packet_interface::CAPABILITY_ENCRYPTION)),
+                YESNO(this->interface_->has_capability(packet_interface::CAPABILITY_RELIABILITY)),
+                YESNO(this->interface_->has_capability(packet_interface::CAPABILITY_SESSION)), this->dictionary_id_);
+  if (this->update_interval_ms_ == SCHEDULER_DONT_RUN) {
+    ESP_LOGCONFIG(TAG, "  Update Interval: never");
+  } else {
+    ESP_LOGCONFIG(TAG, "  Update Interval: %" PRIu32 "ms", this->update_interval_ms_);
+  }
+  if (this->remote_timeout_ms_ != 0) {
+    ESP_LOGCONFIG(TAG, "  Remote Timeout: %" PRIu32 "ms", this->remote_timeout_ms_);
+  }
+  for (const auto &entity : this->entities_) {
+    ESP_LOGCONFIG(TAG, "  %s %u: %s", entity.is_sensor ? LOG_STR_LITERAL("Sensor") : LOG_STR_LITERAL("Binary Sensor"),
+                  entity.number, entity.id);
+  }
+#ifdef ENTITY_TRANSPORT_REMOTE_SENSOR_COUNT
+  for (const auto &remote : this->remote_sensors_) {
+    ESP_LOGCONFIG(TAG, "  Remote Sensor: %s from %s", remote.remote_id, remote.provider);
+  }
+#endif
+#ifdef ENTITY_TRANSPORT_REMOTE_BINARY_SENSOR_COUNT
+  for (const auto &remote : this->remote_binary_sensors_) {
+    ESP_LOGCONFIG(TAG, "  Remote Binary Sensor: %s from %s", remote.remote_id, remote.provider);
+  }
+#endif
+}
+
+void EntityTransport::send_all_() {
+  this->dictionary_pending_ = true;
+  this->dictionary_next_ = 0;
+  this->dictionary_part_ = 0;
+  for (auto &entity : this->entities_)
+    entity.updated = true;
+  this->enable_loop();
+}
+
+void EntityTransport::mark_updated_(LocalEntity &entity) {
+  entity.updated = true;
+  this->enable_loop();
+}
+
+void EntityTransport::loop() {
+  this->disable_loop();
+  // States are only sent once the dictionary that names them has been accepted
+  if ((this->dictionary_pending_ && !this->send_dictionary_()) || !this->send_updated_()) {
+    this->sending_refused_();
+    this->set_timeout(RETRY_TIMER_ID, RETRY_DELAY_MS, [this] { this->enable_loop(); });
+    return;
+  }
+  this->refusing_ = false;
+  if (this->status_has_warning()) {
+    ESP_LOGI(TAG, "Packets are accepted again");
+    this->status_clear_warning();
+  }
+}
+
+// A link that is down or full refuses packets for a while; one that refuses them for long sends nothing at all
+void EntityTransport::sending_refused_() {
+  uint32_t now = App.get_loop_component_start_time();
+  if (!this->refusing_) {
+    this->refusing_ = true;
+    this->refused_since_ms_ = now;
+    return;
+  }
+  if (!this->status_has_warning() && now - this->refused_since_ms_ >= REFUSED_WARNING_MS) {
+    ESP_LOGW(TAG, "The packet interface has accepted no packets for %" PRIu32 "s, so no states are sent",
+             (now - this->refused_since_ms_) / 1000);
+    this->status_set_warning();
+  }
+}
+
+size_t EntityTransport::write_header_(uint8_t type) const {
+  this->buffer_[0] = type;
+  put_uint32(this->buffer_ + 1, this->dictionary_id_);
+  return HEADER_SIZE;
+}
+
+bool EntityTransport::send_dictionary_() {
+  uint8_t *buf = this->buffer_;
+  const auto &name = App.get_name();
+  size_t header = this->write_header_(PACKET_DICTIONARY);
+  size_t part_offset = header++;
+  buf[header++] = name.size();
+  memcpy(buf + header, name.c_str(), name.size());
+  header += name.size();
+  size_t length = header;
+  size_t count_offset = 0;
+  uint8_t section_type = 0;  // none
+  // A dictionary in several packets resumes after the last packet accepted, so a refused one does not resend the rest
+  for (size_t i = this->dictionary_next_; i != this->entities_.size(); i++) {
+    const auto &entity = this->entities_[i];
+    uint8_t type = entity.is_sensor ? TYPE_SENSOR : TYPE_BINARY_SENSOR;
+    size_t id_length = strlen(entity.id);
+    bool new_section = type != section_type;
+    if (length + (new_section ? SECTION_HEADER_SIZE : 0) + 1 + id_length > this->max_packet_size_) {
+      buf[part_offset] = this->dictionary_part_ & PART_INDEX_MASK;
+      if (!this->interface_->send_to_interface(PacketBuffer(buf, length), {})) {
+        ESP_LOGV(TAG, "Dictionary packet of %zu bytes not accepted, will retry", length);
+        return false;
+      }
+      this->dictionary_next_ = i;
+      this->dictionary_part_++;
+      length = header;
+      new_section = true;
+    }
+    if (new_section) {
+      buf[length++] = type;
+      buf[length++] = entity.number;
+      count_offset = length;
+      buf[length++] = 0;
+      section_type = type;
+    }
+    buf[count_offset]++;
+    buf[length++] = id_length;
+    memcpy(buf + length, entity.id, id_length);
+    length += id_length;
+  }
+  if (length != header) {
+    buf[part_offset] = (this->dictionary_part_ & PART_INDEX_MASK) | PART_LAST;
+    if (!this->interface_->send_to_interface(PacketBuffer(buf, length), {})) {
+      ESP_LOGV(TAG, "Dictionary packet of %zu bytes not accepted, will retry", length);
+      return false;
+    }
+  }
+  this->dictionary_pending_ = false;
+  this->dictionary_next_ = 0;
+  this->dictionary_part_ = 0;
+  return true;
+}
+
+// Writes the entity's data record, and returns its size
+size_t EntityTransport::write_record_(const LocalEntity &entity, uint8_t *record) const {
+  uint8_t type = entity.is_sensor ? TYPE_SENSOR : TYPE_BINARY_SENSOR;
+  uint8_t payload = PAYLOAD_NO_STATE;
+  bool value = false;
+  size_t size = TAG_SIZE;
+#ifdef USE_SENSOR
+  if (entity.is_sensor) {
+    float state = static_cast<sensor::Sensor *>(entity.entity)->get_state();
+    if (!std::isnan(state)) {
+      payload = PAYLOAD_WORD;
+      uint32_t bits;
+      memcpy(&bits, &state, sizeof(bits));
+      put_uint32(record + TAG_SIZE, bits);
+      size += WORD_SIZE;
+    }
+  }
+#endif
+#ifdef USE_BINARY_SENSOR
+  if (!entity.is_sensor) {
+    auto *sensor = static_cast<binary_sensor::BinarySensor *>(entity.entity);
+    if (sensor->has_state()) {
+      payload = PAYLOAD_NONE;
+      value = sensor->state;
+    }
+  }
+#endif
+  uint16_t tag =
+      entity.number | (type << TAG_TYPE_SHIFT) | (payload << TAG_PAYLOAD_SHIFT) | (value ? TAG_VALUE_BIT : 0);
+  record[0] = tag;
+  record[1] = tag >> 8;
+  return size;
+}
+
+// Sends every updated entity, in as few packets as fit; returns false if a packet was refused
+bool EntityTransport::send_updated_() {
+  size_t length = this->write_header_(PACKET_DATA);
+  size_t first = 0;
+  for (size_t i = 0; i != this->entities_.size(); i++) {
+    auto &entity = this->entities_[i];
+    if (!entity.updated)
+      continue;
+    uint8_t record[MAX_RECORD_SIZE];
+    size_t size = this->write_record_(entity, record);
+    if (length + size > this->max_packet_size_) {
+      if (!this->flush_(length, first, i))
+        return false;
+      length = HEADER_SIZE;
+      first = i;
+    }
+    memcpy(this->buffer_ + length, record, size);
+    length += size;
+  }
+  return this->flush_(length, first, this->entities_.size());
+}
+
+// Sends the packet holding the updated entities from first up to last, and clears their flags if it was accepted
+bool EntityTransport::flush_(size_t length, size_t first, size_t last) {
+  if (length == HEADER_SIZE)
+    return true;
+  if (!this->interface_->send_to_interface(PacketBuffer(this->buffer_, length), {})) {
+    ESP_LOGV(TAG, "Packet of %zu bytes not accepted, will retry", length);
+    return false;
+  }
+  for (size_t i = first; i != last; i++)
+    this->entities_[i].updated = false;
+  return true;
+}
+
+void EntityTransport::receive_(const PacketBuffer &data) {
+  // Packet interface layers deliver packets in one piece
+  if (!data.is_contiguous()) {
+    ESP_LOGW(TAG, "Packet split across buffers is not supported");
+    return;
+  }
+  auto packet = data.as_span();
+  if (packet.size() < HEADER_SIZE) {
+    if (this->warning_due_()) {
+      ESP_LOGW(TAG, "Packet of %zu bytes is too short", packet.size());
+    }
+    return;
+  }
+  if (packet[0] >> 4 != FORMAT_VERSION) {
+    if (this->warning_due_()) {
+      ESP_LOGW(TAG, "Packet format version %u not supported; the sender may run another ESPHome version",
+               packet[0] >> 4);
+    }
+    return;
+  }
+  uint32_t dictionary_id = encode_uint32(packet[4], packet[3], packet[2], packet[1]);
+  if (dictionary_id == this->dictionary_id_) {
+    // Either a request for our dictionary, or our own packet heard on a broadcast channel
+    if (packet[0] == PACKET_REQUEST && packet.size() == HEADER_SIZE) {
+      ESP_LOGD(TAG, "Dictionary requested");
+      this->send_all_();
+    }
+    return;
+  }
+  if (packet[0] == PACKET_DICTIONARY) {
+    this->receive_dictionary_(packet, dictionary_id);
+  } else if (packet[0] == PACKET_DATA) {
+    this->receive_data_(packet, dictionary_id);
+  } else if (packet[0] != PACKET_REQUEST) {
+    ESP_LOGV(TAG, "Unknown packet type 0x%02X", packet[0]);
+  }
+}
+
+void EntityTransport::receive_dictionary_(std::span<const uint8_t> packet, uint32_t dictionary_id) {
+  if (!dictionary_well_formed(packet)) {
+    if (this->warning_due_()) {
+      ESP_LOGW(TAG, "Dictionary packet of %zu bytes is malformed", packet.size());
+    }
+    return;
+  }
+  size_t pos = HEADER_SIZE;
+  uint8_t part = packet[pos++];
+  uint8_t index = part & PART_INDEX_MASK;
+  // The dictionary is complete, and need not be asked for again, once its last part follows all the others in order
+  bool in_order = index == 0 || (this->rx_dictionary_id_ == dictionary_id && index == this->rx_next_part_);
+  this->rx_dictionary_id_ = dictionary_id;
+  this->rx_next_part_ = in_order ? (index + 1) & PART_INDEX_MASK : PART_NONE;
+  bool completed = in_order && (part & PART_LAST) != 0;
+  bool first_time = completed && !this->dictionary_seen_(dictionary_id);
+  if (first_time) {
+    this->seen_dictionaries_[this->seen_next_] = dictionary_id;
+    this->seen_next_ = (this->seen_next_ + 1) % this->seen_dictionaries_.size();
+  }
+  size_t provider_length = packet[pos++];
+  const auto *provider = reinterpret_cast<const char *>(packet.data() + pos);
+  pos += provider_length;
+  while (pos != packet.size()) {
+    uint8_t type = packet[pos];
+    uint8_t number = packet[pos + 1];
+    uint8_t count = packet[pos + 2];
+    pos += SECTION_HEADER_SIZE;
+    for (uint8_t i = 0; i != count; i++) {
+      size_t id_length = packet[pos++];
+      this->learn_(provider, provider_length, type, number + i, reinterpret_cast<const char *>(packet.data() + pos),
+                   id_length, dictionary_id);
+      pos += id_length;
+    }
+  }
+  // A provider may go back to a dictionary already seen, so every complete one is checked
+  if (completed)
+    this->forget_unnamed_(provider, provider_length, dictionary_id, first_time);
+}
+
+void EntityTransport::forget_unnamed_(const char *provider, size_t provider_length, uint32_t dictionary_id,
+                                      bool first_time) {
+  // A remote entity that its provider's whole dictionary does not name would otherwise keep no or a stale state
+  // silently
+#ifdef ENTITY_TRANSPORT_REMOTE_SENSOR_COUNT
+  for (auto &remote : this->remote_sensors_) {
+    if (!matches(remote.provider, provider, provider_length) || (remote.known && remote.dictionary_id == dictionary_id))
+      continue;
+    if (remote.known || first_time) {
+      ESP_LOGW(TAG, "'%s' does not send '%s'", remote.provider, remote.remote_id);
+    }
+    remote.known = false;
+    if (remote.has_state) {
+      remote.has_state = false;
+      remote.entity->publish_state(NAN);
+    }
+  }
+#endif
+#ifdef ENTITY_TRANSPORT_REMOTE_BINARY_SENSOR_COUNT
+  for (auto &remote : this->remote_binary_sensors_) {
+    if (!matches(remote.provider, provider, provider_length) || (remote.known && remote.dictionary_id == dictionary_id))
+      continue;
+    if (remote.known || first_time) {
+      ESP_LOGW(TAG, "'%s' does not send '%s'", remote.provider, remote.remote_id);
+    }
+    remote.known = false;
+    if (remote.has_state) {
+      remote.has_state = false;
+      remote.entity->invalidate_state();
+    }
+  }
+#endif
+}
+
+void EntityTransport::learn_(const char *provider, size_t provider_length, uint8_t type, uint8_t number, const char *id,
+                             size_t id_length, uint32_t dictionary_id) {
+#ifdef ENTITY_TRANSPORT_REMOTE_SENSOR_COUNT
+  if (type == TYPE_SENSOR) {
+    for (auto &remote : this->remote_sensors_) {
+      if (matches(remote.provider, provider, provider_length) && matches(remote.remote_id, id, id_length)) {
+        remote.dictionary_id = dictionary_id;
+        remote.number = number;
+        remote.known = true;
+      }
+    }
+  }
+#endif
+#ifdef ENTITY_TRANSPORT_REMOTE_BINARY_SENSOR_COUNT
+  if (type == TYPE_BINARY_SENSOR) {
+    for (auto &remote : this->remote_binary_sensors_) {
+      if (matches(remote.provider, provider, provider_length) && matches(remote.remote_id, id, id_length)) {
+        remote.dictionary_id = dictionary_id;
+        remote.number = number;
+        remote.known = true;
+      }
+    }
+  }
+#endif
+}
+
+bool EntityTransport::dictionary_seen_(uint32_t dictionary_id) const {
+  return std::find(this->seen_dictionaries_.begin(), this->seen_dictionaries_.end(), dictionary_id) !=
+         this->seen_dictionaries_.end();
+}
+
+void EntityTransport::receive_data_(std::span<const uint8_t> packet, uint32_t dictionary_id) {
+  bool known = false;
+  bool has_remotes = false;
+#ifdef ENTITY_TRANSPORT_REMOTE_SENSOR_COUNT
+  for (const auto &remote : this->remote_sensors_) {
+    known |= remote.known && remote.dictionary_id == dictionary_id;
+    has_remotes = true;
+  }
+#endif
+#ifdef ENTITY_TRANSPORT_REMOTE_BINARY_SENSOR_COUNT
+  for (const auto &remote : this->remote_binary_sensors_) {
+    known |= remote.known && remote.dictionary_id == dictionary_id;
+    has_remotes = true;
+  }
+#endif
+  if (!has_remotes)
+    return;
+  // Checked first, so a damaged packet does not make the provider resend everything
+  if (!data_well_formed(packet)) {
+    if (this->warning_due_()) {
+      ESP_LOGW(TAG, "Data packet of %zu bytes is malformed", packet.size());
+    }
+    return;
+  }
+  // A dictionary not yet received in full may name our entities, or be a provider's new one; one received in full
+  // named all of them it could, so asking again would only make that provider resend everything
+  if (!this->dictionary_seen_(dictionary_id))
+    this->request_dictionary_(dictionary_id);
+  if (!known)
+    return;
+  [[maybe_unused]] uint32_t now = App.get_loop_component_start_time();
+  for (size_t pos = HEADER_SIZE; pos != packet.size(); pos += record_size(packet, pos)) {
+    [[maybe_unused]] Record record = parse_record(packet, pos);
+#ifdef ENTITY_TRANSPORT_REMOTE_SENSOR_COUNT
+    if (record.type == TYPE_SENSOR) {
+      float value = NAN;
+      if (record.payload == PAYLOAD_WORD) {
+        uint32_t bits = encode_uint32(record.data[3], record.data[2], record.data[1], record.data[0]);
+        memcpy(&value, &bits, sizeof(value));
+      }
+      for (auto &remote : this->remote_sensors_) {
+        if (remote.known && remote.dictionary_id == dictionary_id && remote.number == record.number) {
+          remote.last_state_ms = now;
+          remote.has_state = true;
+          remote.entity->publish_state(value);
+        }
+      }
+    }
+#endif
+#ifdef ENTITY_TRANSPORT_REMOTE_BINARY_SENSOR_COUNT
+    if (record.type == TYPE_BINARY_SENSOR) {
+      for (auto &remote : this->remote_binary_sensors_) {
+        if (!remote.known || remote.dictionary_id != dictionary_id || remote.number != record.number)
+          continue;
+        remote.last_state_ms = now;
+        remote.has_state = true;
+        if (record.payload == PAYLOAD_NO_STATE) {
+          remote.entity->invalidate_state();
+        } else {
+          remote.entity->publish_state(record.value);
+        }
+      }
+    }
+#endif
+  }
+}
+
+void EntityTransport::request_dictionary_(uint32_t dictionary_id) {
+  uint32_t now = App.get_loop_component_start_time();
+  if (this->request_sent_ && now - this->last_request_ms_ < REQUEST_INTERVAL_MS)
+    return;
+  uint8_t packet[HEADER_SIZE] = {PACKET_REQUEST};
+  put_uint32(packet + 1, dictionary_id);
+  // A refused request is tried again with the next data packet under that dictionary id
+  if (!this->interface_->send_to_interface(PacketBuffer(packet, sizeof(packet)), {})) {
+    ESP_LOGV(TAG, "Request for dictionary %08" PRIX32 " not accepted", dictionary_id);
+    return;
+  }
+  this->request_sent_ = true;
+  this->last_request_ms_ = now;
+  ESP_LOGD(TAG, "Requested dictionary %08" PRIX32, dictionary_id);
+}
+
+// Dropped packets point to a device with other firmware or a fault, and may arrive steadily, so warn only now and then
+bool EntityTransport::warning_due_() {
+  uint32_t now = App.get_loop_component_start_time();
+  if (this->warned_ && now - this->last_warning_ms_ < WARNING_INTERVAL_MS)
+    return false;
+  this->warned_ = true;
+  this->last_warning_ms_ = now;
+  return true;
+}
+
+// A newly connected or restarted peer needs the dictionary and every state; while it is lost, its entities have no
+// state
+void EntityTransport::on_session_(bool connected) {
+  if (connected) {
+    this->send_all_();
+    return;
+  }
+  this->clear_remote_states_(false);
+}
+
+// Clears the state of every remote entity, or with timed_out_only, of those whose state is older than the timeout
+void EntityTransport::clear_remote_states_(bool timed_out_only) {
+  [[maybe_unused]] uint32_t now = App.get_loop_component_start_time();
+#ifdef ENTITY_TRANSPORT_REMOTE_SENSOR_COUNT
+  for (auto &remote : this->remote_sensors_) {
+    if (timed_out_only && (!remote.has_state || now - remote.last_state_ms <= this->remote_timeout_ms_))
+      continue;
+    remote.has_state = false;
+    remote.entity->publish_state(NAN);
+  }
+#endif
+#ifdef ENTITY_TRANSPORT_REMOTE_BINARY_SENSOR_COUNT
+  for (auto &remote : this->remote_binary_sensors_) {
+    if (timed_out_only && (!remote.has_state || now - remote.last_state_ms <= this->remote_timeout_ms_))
+      continue;
+    remote.has_state = false;
+    remote.entity->invalidate_state();
+  }
+#endif
+}
+
+}  // namespace esphome::entity_transport

esphome/components/entity_transport/entity_transport.h

@@ -0,0 +1,171 @@
+#pragma once
+
+#include <array>
+#include <span>
+
+#include "esphome/components/packet_interface/packet_interface.h"
+#include "esphome/core/component.h"
+#include "esphome/core/defines.h"
+#include "esphome/core/entity_base.h"
+#include "esphome/core/helpers.h"
+#ifdef USE_SENSOR
+#include "esphome/components/sensor/sensor.h"
+#endif
+#ifdef USE_BINARY_SENSOR
+#include "esphome/components/binary_sensor/binary_sensor.h"
+#endif
+
+namespace esphome::entity_transport {
+
+/**
+ * Sends the states of local sensors and binary sensors over a packet interface, and publishes the states received
+ * from other devices to remote entities.
+ *
+ * Each device numbers its sensors and its binary sensors from 0, and sends a dictionary that gives the id for each
+ * number. Data packets then refer to an entity by its number. Every packet carries the sender's dictionary id, a hash
+ * of its device name and dictionary, so that a receiver knows which device sent it and which dictionary applies.
+ * All values are little endian.
+ *
+ * Dictionary packet:
+ * - type: 1 byte, PACKET_DICTIONARY;
+ * - dictionary id: 4 bytes;
+ * - part: 1 byte, the packet's index in the dictionary in bits 0-6, counting from 0 and wrapping, and bit 7 set on
+ *   the last packet;
+ * - sender's device name: length (1 byte), then the name;
+ * - one or more sections, each: entity type (1 byte), first number (1 byte), count (1 byte), then for each entity
+ *   its id: length (1 byte), then the id.
+ *
+ * Data packet:
+ * - type: 1 byte, PACKET_DATA;
+ * - dictionary id: 4 bytes;
+ * - records, to the end, each a 16-bit tag, then its payload. The tag holds the entity's number in bits 0-7, its type
+ *   in bits 8-12, and the payload form in bits 13-14: none, with the state in bit 15 (binary sensors); 4 bytes (a
+ *   sensor's float); a length byte, then that many bytes; or no state, with no payload. The form gives the record's
+ *   size, so a receiver skips records of types it does not know.
+ *
+ * Every packet is checked in full before anything in it is used, so a damaged or forged packet changes no state.
+ *
+ * Dictionary request packet, sent by a device that receives data with a dictionary id it has not received in full,
+ * with every part in order:
+ * - type: 1 byte, PACKET_REQUEST;
+ * - the dictionary id wanted: 4 bytes.
+ *
+ * Changed states are sent from loop(). The dictionary and all states are sent at boot, when a session layer reports
+ * the peer connected, when the dictionary is requested, and every update interval. Unless the interface has both a
+ * session and a reliability layer, the update interval defaults to DEFAULT_UPDATE_INTERVAL_MS. When the interface
+ * refuses a packet, sending is tried again after a delay, and a warning is set once it has refused every packet for a
+ * minute. With a remote timeout, a remote entity loses its state when
+ * none arrives for it within the timeout.
+ */
+class EntityTransport : public Component {
+ public:
+  explicit EntityTransport(packet_interface::PacketInterface *interface) : interface_(interface) {}
+
+  void setup() override;
+  void loop() override;
+  void dump_config() override;
+
+  /// 0 chooses the default for the interface's layers; SCHEDULER_DONT_RUN never resends.
+  void set_update_interval(uint32_t interval_ms) { this->update_interval_ms_ = interval_ms; }
+  /// Remote entities lose their state when none arrives for this long; 0 keeps the last state.
+  void set_remote_timeout(uint32_t timeout_ms) { this->remote_timeout_ms_ = timeout_ms; }
+  void set_entity_count(size_t count) { this->entities_.init(count); }
+  // Sensors must be added before binary sensors, so that data packets hold sensor records first
+#ifdef USE_SENSOR
+  void add_sensor(const char *id, sensor::Sensor *sensor) {
+    this->entities_.push_back({sensor, id, this, this->sensor_count_++, true, true});
+  }
+#endif
+#ifdef USE_BINARY_SENSOR
+  void add_binary_sensor(const char *id, binary_sensor::BinarySensor *sensor) {
+    this->entities_.push_back({sensor, id, this, this->binary_sensor_count_++, false, true});
+  }
+#endif
+#ifdef ENTITY_TRANSPORT_REMOTE_SENSOR_COUNT
+  void add_remote_sensor(const char *provider, const char *remote_id, sensor::Sensor *sensor) {
+    this->remote_sensors_.push_back({provider, remote_id, sensor});
+  }
+#endif
+#ifdef ENTITY_TRANSPORT_REMOTE_BINARY_SENSOR_COUNT
+  void add_remote_binary_sensor(const char *provider, const char *remote_id, binary_sensor::BinarySensor *sensor) {
+    this->remote_binary_sensors_.push_back({provider, remote_id, sensor});
+  }
+#endif
+
+ protected:
+  struct LocalEntity {
+    EntityBase *entity;  // a sensor::Sensor or a binary_sensor::BinarySensor, as is_sensor says
+    const char *id;
+    EntityTransport *parent;
+    uint8_t number;
+    bool is_sensor;
+    bool updated;
+  };
+  template<typename T> struct RemoteEntity {
+    const char *provider;
+    const char *remote_id;
+    T *entity;
+    uint32_t dictionary_id{0};  // learnt from the provider's dictionary
+    uint32_t last_state_ms{0};
+    uint8_t number{0};
+    bool known{false};
+    bool has_state{false};  // a state arrived, and has not yet timed out
+  };
+
+  void send_all_();
+  void mark_updated_(LocalEntity &entity);
+  bool send_dictionary_();
+  bool send_updated_();
+  size_t write_record_(const LocalEntity &entity, uint8_t *record) const;
+  bool flush_(size_t length, size_t first, size_t last);
+  size_t write_header_(uint8_t type) const;
+  void receive_(const packet_interface::PacketBuffer &data);
+  void receive_dictionary_(std::span<const uint8_t> packet, uint32_t dictionary_id);
+  void receive_data_(std::span<const uint8_t> packet, uint32_t dictionary_id);
+  void learn_(const char *provider, size_t provider_length, uint8_t type, uint8_t number, const char *id,
+              size_t id_length, uint32_t dictionary_id);
+  void request_dictionary_(uint32_t dictionary_id);
+  bool dictionary_seen_(uint32_t dictionary_id) const;
+  /// Clears each remote entity of \p provider that its complete dictionary does not name, warning if the entity was
+  /// known or the dictionary is \p first_time seen, so a resent dictionary does not repeat the warning.
+  void forget_unnamed_(const char *provider, size_t provider_length, uint32_t dictionary_id, bool first_time);
+  bool warning_due_();
+  void sending_refused_();
+  void on_session_(bool connected);
+  void clear_remote_states_(bool timed_out_only);
+
+  packet_interface::PacketInterface *interface_;
+  FixedVector<LocalEntity> entities_;
+#ifdef ENTITY_TRANSPORT_REMOTE_SENSOR_COUNT
+  StaticVector<RemoteEntity<sensor::Sensor>, ENTITY_TRANSPORT_REMOTE_SENSOR_COUNT> remote_sensors_;
+#endif
+#ifdef ENTITY_TRANSPORT_REMOTE_BINARY_SENSOR_COUNT
+  StaticVector<RemoteEntity<binary_sensor::BinarySensor>, ENTITY_TRANSPORT_REMOTE_BINARY_SENSOR_COUNT>
+      remote_binary_sensors_;
+#endif
+  // Packets are built here, allocated in setup()
+  uint8_t *buffer_{nullptr};
+  size_t max_packet_size_{0};
+  uint32_t update_interval_ms_{0};
+  uint32_t remote_timeout_ms_{0};
+  uint32_t dictionary_id_{0};
+  uint32_t last_request_ms_{0};
+  uint32_t last_warning_ms_{0};
+  uint32_t refused_since_ms_{0};  // when the interface began refusing every packet
+  uint32_t rx_dictionary_id_{0};  // the dictionary whose parts are arriving
+  // The last dictionary ids received in full, so a provider whose dictionary names none of our entities is not asked
+  // again
+  std::array<uint32_t, 8> seen_dictionaries_{};
+  uint8_t seen_next_{0};
+  uint8_t rx_next_part_{0};     // the index of its next part, or PART_NONE if one was missed
+  uint8_t dictionary_part_{0};  // the index of the next dictionary packet to send
+  uint8_t sensor_count_{0};
+  uint8_t binary_sensor_count_{0};
+  size_t dictionary_next_{0};  // the first entity of the next dictionary packet to send
+  bool dictionary_pending_{true};
+  bool request_sent_{false};
+  bool warned_{false};
+  bool refusing_{false};
+};
+
+}  // namespace esphome::entity_transport

esphome/components/entity_transport/sensor.py

@@ -0,0 +1,11 @@
+from esphome.components import sensor
+from esphome.types import ConfigType
+
+from . import register_remote_sensor, remote_entity_schema
+
+CONFIG_SCHEMA = remote_entity_schema(sensor.sensor_schema())
+
+
+async def to_code(config: ConfigType) -> None:
+    var = await sensor.new_sensor(config)
+    await register_remote_sensor(config, var)

esphome/components/epaper_spi/epaper_spi.cpp

@@ -1,5 +1,4 @@
 #include "epaper_spi.h"
-#include <algorithm>
 #include <cinttypes>
 #include "esphome/core/application.h"
 #include "esphome/core/helpers.h"
@@ -38,42 +37,6 @@ bool EPaperBase::init_buffer_(size_t buffer_length) {
   return true;
 }
 
-bool EPaperBase::init_sent_frame_(size_t length) {
-  if (!this->is_using_partial_update_())
-    return false;
-  if (this->sent_.init(length))
-    return true;
-  ESP_LOGW(TAG, "No memory for the previous frame; partial updates will send the whole drawn area");
-  return false;
-}
-
-uint32_t EPaperBase::buffer_hash_() const {
-  uint32_t hash = FNV1_OFFSET_BASIS;
-  size_t index = 0;
-  while (index != this->buffer_.size()) {
-    size_t length;
-    const uint8_t *data = this->buffer_.get_span(index, length);
-    for (size_t i = 0; i != length; i++)
-      hash = fnv1a_hash_extend(hash, data[i]);
-    index += length;
-  }
-  return hash;
-}
-
-void EPaperBase::set_full_bounds_() {
-  this->x_low_ = 0;
-  this->y_low_ = 0;
-  this->x_high_ = this->width_;
-  this->y_high_ = this->height_;
-}
-
-void EPaperBase::reset_bounds_() {
-  this->x_low_ = this->width_;
-  this->x_high_ = 0;
-  this->y_low_ = this->height_;
-  this->y_high_ = 0;
-}
-
 void EPaperBase::setup_pins_() const {
   for (auto *pin : this->enable_pins_) {
     pin->setup();
@@ -270,28 +233,17 @@ void EPaperBase::process_state_() {
         // Refresh the whole panel even if nothing was drawn
         this->full_update_requested_ = false;
         this->update_count_ = 0;
-        this->set_full_bounds_();
+        this->x_low_ = 0;
+        this->y_low_ = 0;
+        this->x_high_ = this->width_;
+        this->y_high_ = this->height_;
       }
       if (this->x_high_ < this->x_low_ || this->y_high_ < this->y_low_) {
         this->set_state_(EPaperState::IDLE);
         return;
       }
-      if (this->is_using_partial_update_()) {
-        const uint32_t frame_hash = this->buffer_hash_();
-        if (this->update_count_ != 0 && this->shown_hash_valid_ && frame_hash == this->shown_hash_) {
-          ESP_LOGD(TAG, "Frame unchanged, refresh skipped");
-          this->reset_bounds_();
-          this->set_state_(EPaperState::IDLE);
-          return;
-        }
-        this->shown_hash_ = frame_hash;
-      }
-      this->drawn_since_hash_ = false;
-      // Valid again only once this frame is on the panel, so an abandoned update leaves nothing to match
-      this->shown_hash_valid_ = false;
       // A full update resets update_count_ to zero, so a non-zero count marks a partial one
       this->partial_ = this->update_count_ != 0;
-      this->sent_count_ = 0;
       this->set_state_(EPaperState::RESET);
       break;
     case EPaperState::INITIALISE:
@@ -304,15 +256,10 @@ void EPaperBase::process_state_() {
       if (!this->transfer_data()) {
         return;  // Not done yet, come back next loop
       }
-      if (this->sent_.is_valid() && this->sent_count_ == this->sent_.size())
-        this->sent_valid_ = true;
-      // A draw during the chunked push may not have reached the panel, so the next update sends the whole frame
-      this->sent_hash_intact_ = this->is_using_partial_update_() && !this->drawn_since_hash_;
-      if (this->drawn_since_hash_) {
-        this->set_full_bounds_();
-      } else {
-        this->reset_bounds_();
-      }
+      this->x_low_ = this->width_;
+      this->x_high_ = 0;
+      this->y_low_ = this->height_;
+      this->y_high_ = 0;
       this->set_state_(EPaperState::POWER_ON);
       break;
     case EPaperState::POWER_ON:
@@ -333,7 +280,6 @@ void EPaperBase::process_state_() {
       break;
     case EPaperState::DEEP_SLEEP:
       this->deep_sleep();
-      this->shown_hash_valid_ = this->sent_hash_intact_;
       this->status_clear_warning();
       this->set_state_(EPaperState::IDLE);
       ESP_LOGD(TAG, "Display update took %" PRIu32 " ms", millis() - this->update_start_time_);
@@ -419,7 +365,6 @@ bool EPaperBase::rotate_coordinates_(int &x, int &y) {
   this->x_high_ = clamp_at_least(this->x_high_, x + 1);
   this->y_low_ = clamp_at_most(this->y_low_, y);
   this->y_high_ = clamp_at_least(this->y_high_, y + 1);
-  this->drawn_since_hash_ = true;
   return true;
 }
 
@@ -541,7 +486,6 @@ void HOT EPaperBase::draw_rgb565_block_(uint8_t *buffer, int x_start, int y_star
   this->x_high_ = clamp_at_least(this->x_high_, x_high);
   this->y_low_ = clamp_at_most(this->y_low_, y_low);
   this->y_high_ = clamp_at_least(this->y_high_, y_high);
-  this->drawn_since_hash_ = true;
 }
 
 // Writes an RGB565 block of pixels, as LVGL sends them, straight into a 1 bit per pixel buffer that is one block (the

esphome/components/epaper_spi/epaper_spi.h

@@ -99,7 +99,10 @@ class EPaperBase : public Display,
 
     // We store 8 pixels per byte
     this->buffer_.fill(pixel_color);
-    this->mark_all_drawn_();
+    this->x_high_ = this->width_;
+    this->y_high_ = this->height_;
+    this->x_low_ = 0;
+    this->y_low_ = 0;
   }
 
   void clear() override {
@@ -136,25 +139,6 @@ class EPaperBase : public Display,
   void wait_for_idle_(bool should_wait);
   void abandon_update_();
   bool init_buffer_(size_t buffer_length);
-  // Allocates the copy of the previous frame; only drivers that diff against it (needs_previous_frame) call this
-  bool init_sent_frame_(size_t length);
-  void record_sent_(size_t index, const uint8_t *data, size_t length) {
-    if (this->sent_.is_valid()) {
-      this->sent_.write(index, data, length);
-      this->sent_count_ += length;
-    }
-  }
-  // Whether the driver reads the previous frame (sent_) for its differential refresh
-  virtual bool needs_previous_frame() const { return false; }
-  // FNV-1a hash of the current frame buffer, to detect an unchanged frame without a full copy
-  uint32_t buffer_hash_() const;
-  void reset_bounds_();
-  void set_full_bounds_();
-  // For a draw that writes the whole buffer without going through rotate_coordinates_()
-  void mark_all_drawn_() {
-    this->set_full_bounds_();
-    this->drawn_since_hash_ = true;
-  }
   void update_effective_transform_();
   bool rotate_coordinates_(int &x, int &y);
   void draw_rgb565_block_(uint8_t *buffer, int x_start, int y_start, int w, int h, const uint8_t *ptr, bool big_endian,
@@ -216,13 +200,6 @@ class EPaperBase : public Display,
   size_t buffer_length_;
   size_t current_data_index_{};  // used by data transfer to track progress
   split_buffer::SplitBuffer buffer_{};
-  split_buffer::SplitBuffer sent_{};  // the previous frame, kept only by drivers that diff against it
-  bool sent_valid_{};                 // sent_ holds a whole frame
-  size_t sent_count_{};               // bytes recorded into sent_ by the update in progress
-  uint32_t shown_hash_{};             // hash of the frame on the panel, to skip an unchanged update
-  bool shown_hash_valid_{};           // shown_hash_ holds the hash of a frame whose refresh completed
-  bool sent_hash_intact_{};           // the buffer was unchanged by the end of the push of shown_hash_
-  bool drawn_since_hash_{};           // something was drawn after shown_hash_ was taken
   GPIOPin *dc_pin_{};
   GPIOPin *busy_pin_{};
   GPIOPin *reset_pin_{};

esphome/components/epaper_spi/epaper_spi_4bpp.cpp

@@ -18,7 +18,11 @@ void EPaper4bpp::fill(Color color) {
   // We store 2 pixels per byte
   this->buffer_.fill(pixel_color + (pixel_color << 4));
 
-  this->mark_all_drawn_();
+  // Whole buffer just changed; mark the entire canvas dirty.
+  this->x_low_ = 0;
+  this->y_low_ = 0;
+  this->x_high_ = this->width_;
+  this->y_high_ = this->height_;
 }
 
 void EPaper4bpp::clear() {

esphome/components/epaper_spi/epaper_spi_inkplate2.cpp

@@ -71,7 +71,10 @@ void EPaperInkplate2::fill(Color color) {
   for (size_t i = half_buffer; i < this->buffer_length_; i++)
     this->buffer_[i] = red_byte;
 
-  this->mark_all_drawn_();
+  this->x_low_ = 0;
+  this->y_low_ = 0;
+  this->x_high_ = this->width_;
+  this->y_high_ = this->height_;
 }
 
 void EPaperInkplate2::clear() { this->fill(COLOR_ON); }

esphome/components/epaper_spi/epaper_spi_jd79660.cpp

@@ -30,7 +30,6 @@ void EPaperJD79660::fill(Color color) {
 
   // We store 4 pixels per byte
   this->buffer_.fill(pixel_color | (pixel_color << 2) | (pixel_color << 4) | (pixel_color << 6));
-  this->drawn_since_hash_ = true;
 }
 
 void HOT EPaperJD79660::draw_pixel_at(int x, int y, Color color) {

esphome/components/epaper_spi/epaper_spi_mono.cpp

@@ -7,12 +7,6 @@
 namespace esphome::epaper_spi {
 ESPHOME_LOG_TAG(TAG, "epaper_spi.mono");
 
-void EPaperMono::setup() {
-  EPaperBase::setup();
-  if (!this->is_failed() && this->needs_previous_frame())
-    this->init_sent_frame_(this->sent_frame_length());
-}
-
 void EPaperMono::refresh_screen(bool partial) {
   ESP_LOGV(TAG, "Refresh screen");
   this->cmd_data(0x22, {partial ? (uint8_t) 0xFF : (uint8_t) 0xF7});
@@ -72,8 +66,7 @@ bool HOT EPaperMono::transfer_data() {
   ESP_LOGV(TAG, "Writing %u bytes at line %zu at %ums", row_length, this->current_data_index_, (unsigned) millis());
   this->start_data_();
   while (this->current_data_index_ != this->y_high_) {
-    const size_t row_start = this->current_data_index_ * this->row_width_ + this->x_low_ / 8;
-    size_t data_idx = row_start;
+    size_t data_idx = this->current_data_index_ * this->row_width_ + this->x_low_ / 8;
     for (size_t i = 0; i != row_length; i++) {
       bytes_to_send[i] = this->send_red_ && !this->send_red_as_image_ ? 0 : this->buffer_[data_idx++];
     }

esphome/components/epaper_spi/epaper_spi_mono.h

@@ -12,8 +12,6 @@ class EPaperMono : public EPaperBase {
              size_t init_sequence_length, DisplayType display_type = DISPLAY_TYPE_BINARY, uint8_t bits_per_pixel = 1)
       : EPaperBase(name, width, height, init_sequence, init_sequence_length, display_type, bits_per_pixel) {}
 
-  void setup() override;
-
  protected:
   void refresh_screen(bool partial) override;
   void power_on() override {}
@@ -21,8 +19,6 @@ class EPaperMono : public EPaperBase {
   void deep_sleep() override;
   bool reset() override;
   virtual void set_window();
-  // Bytes in the comparison frame; the buffer's size unless a subclass sends the frame in another layout
-  virtual size_t sent_frame_length() const { return this->buffer_length_; }
   bool transfer_data() override;
   bool send_red_{true};
   bool software_reset_{true};  // send 0x12 after the hardware reset

esphome/components/epaper_spi/epaper_spi_ssd1677.cpp

@@ -6,6 +6,21 @@
 #include "esphome/core/log.h"
 
 namespace esphome::epaper_spi {
+ESPHOME_LOG_TAG(TAG, "epaper_spi.ssd1677");
+
+void EPaperSSD1677::setup() {
+  EPaperMono::setup();
+  if (!this->is_failed())
+    this->init_comparison_frame_();
+}
+
+void EPaperSSD1677::init_comparison_frame_() {
+  if (!this->is_using_partial_update_())
+    return;
+  if (!this->sent_.init(this->plane_row_length_() * this->height_)) {
+    ESP_LOGW(TAG, "No memory for the comparison frame; partial updates will degrade unchanged areas");
+  }
+}
 
 void EPaperSSD1677::plane_row(size_t y, uint8_t *out) {
   const size_t row_length = this->plane_row_length_();
@@ -67,7 +82,7 @@ bool HOT EPaperSSD1677::transfer_data() {
     }
     this->write_array(data, length);
     if (this->plane_ == 1)
-      this->record_sent_(this->current_data_index_, data, length);
+      this->sent_.write(this->current_data_index_, data, length);
     this->current_data_index_ += length;
     if (this->current_data_index_ != plane_length && millis() - start_time > MAX_TRANSFER_TIME) {
       // Let the main loop run and come back next loop

esphome/components/epaper_spi/epaper_spi_ssd1677.h

@@ -26,12 +26,12 @@ class EPaperSSD1677 : public EPaperMono {
                 size_t init_sequence_length, DisplayType display_type = DISPLAY_TYPE_BINARY, uint8_t bits_per_pixel = 1)
       : EPaperMono(name, width, height, init_sequence, init_sequence_length, display_type, bits_per_pixel) {}
 
+  void setup() override;
+
  protected:
-  // Reads the previous frame to copy it into the other RAM bank on a full refresh
-  bool needs_previous_frame() const override { return true; }
-  // Allocates the comparison frame as setup() would, for tests that run without a bus.
-  void init_comparison_frame_() { this->init_sent_frame_(this->sent_frame_length()); }
-  size_t sent_frame_length() const override { return this->plane_row_length_() * this->height_; }
+  // Allocates the comparison frame when partial updates are enabled. Separate from setup() so it
+  // can run without a bus.
+  void init_comparison_frame_();
   // Bytes in one row of a RAM plane: 8 pixels per byte, whatever the buffer holds.
   size_t plane_row_length_() const { return (this->width_ + 7) / 8; }
   // Row y of the frame as a RAM plane holds it, 1 bit per pixel with 1 = white.
@@ -39,7 +39,8 @@ class EPaperSSD1677 : public EPaperMono {
   bool reset() override;
   bool transfer_data() override;
 
-  uint8_t plane_{0};  // 0 while sending 0x26, 1 while sending 0x24
+  split_buffer::SplitBuffer sent_{};  // the frame last sent to 0x24, i.e. what the panel shows
+  uint8_t plane_{0};                  // 0 while sending 0x26, 1 while sending 0x24
 };
 
 }  // namespace esphome::epaper_spi

esphome/components/epaper_spi/epaper_spi_ssd1677_gray4.cpp

@@ -29,7 +29,10 @@ void EPaperSSD1677Gray4::fill(Color color) {
   }
   const uint8_t level = color_to_gray4(color);
   this->buffer_.fill((uint8_t) (level | (level << 2) | (level << 4) | (level << 6)));
-  this->mark_all_drawn_();
+  this->x_low_ = 0;
+  this->y_low_ = 0;
+  this->x_high_ = this->width_;
+  this->y_high_ = this->height_;
 }
 
 void HOT EPaperSSD1677Gray4::draw_pixel_at(int x, int y, Color color) {
@@ -80,14 +83,14 @@ bool HOT EPaperSSD1677Gray4::transfer_data() {
   this->start_data_();
   while (this->current_data_index_ != this->y_high_) {
     const size_t src_row = this->current_data_index_ * this->row_width_ + this->x_low_ / 4;
-    for (size_t i = 0; i != plane_row_length; i++)
-      bytes_to_send[i] = plane_byte(this->buffer_[src_row + 2 * i], this->buffer_[src_row + 2 * i + 1], first_pass);
-    // What the next partial update compares against: the high bits, as a black-and-white frame.
-    if (first_pass)
-      this->record_sent_(this->current_data_index_ * plane_row_length, bytes_to_send, plane_row_length);
-    // The OTP grayscale waveform treats data as inverted relative to monochrome
-    for (size_t i = 0; i != plane_row_length; i++)
-      bytes_to_send[i] = (uint8_t) ~bytes_to_send[i];
+    for (size_t i = 0; i != plane_row_length; i++) {
+      const uint8_t plane = plane_byte(this->buffer_[src_row + 2 * i], this->buffer_[src_row + 2 * i + 1], first_pass);
+      // The OTP grayscale waveform treats data as inverted relative to monochrome
+      bytes_to_send[i] = (uint8_t) ~plane;
+      // What the next partial update compares against: the high bits, as a black-and-white frame.
+      if (first_pass && this->sent_.is_valid())
+        this->sent_[this->current_data_index_ * plane_row_length + i] = plane;
+    }
     ++this->current_data_index_;
     this->write_array(bytes_to_send, plane_row_length);
     if (millis() - start_time > MAX_TRANSFER_TIME) {

esphome/components/epaper_spi/epaper_spi_ssd1681.cpp

@@ -1,50 +1,10 @@
 #include "epaper_spi_ssd1681.h"
 
-#include <algorithm>
-#include <cstring>
-
 #include "esphome/core/log.h"
 
 namespace esphome::epaper_spi {
 ESPHOME_LOG_TAG(TAG, "epaper_spi.ssd1681");
 
-void EPaperSSD1681::bounds_from_changes_() {
-  if (!this->sent_valid_ || this->sent_.size() != this->buffer_.size())
-    return;
-  bool changed = false;
-  uint16_t row_low = this->height_, row_high = 0, col_low = this->row_width_, col_high = 0;
-  for (uint16_t row = 0; row != this->height_; row++) {
-    const size_t base = row * this->row_width_;
-    const size_t end = base + this->row_width_;
-    size_t index = base;
-    while (index != end) {
-      size_t new_length, old_length;
-      const uint8_t *new_bytes = this->buffer_.get_span(index, new_length);
-      const uint8_t *old_bytes = this->sent_.get_span(index, old_length);
-      const size_t length = std::min({new_length, old_length, end - index});
-      if (std::memcmp(new_bytes, old_bytes, length) != 0) {
-        for (size_t i = 0; i != length; i++) {
-          if (new_bytes[i] == old_bytes[i])
-            continue;
-          const auto col = static_cast<uint16_t>(index + i - base);
-          changed = true;
-          row_low = std::min(row_low, row);
-          row_high = std::max<uint16_t>(row_high, row + 1);
-          col_low = std::min(col_low, col);
-          col_high = std::max<uint16_t>(col_high, col + 1);
-        }
-      }
-      index += length;
-    }
-  }
-  if (!changed)
-    return;
-  this->x_low_ = col_low * 8;
-  this->x_high_ = std::min<uint16_t>(col_high * 8, this->width_);
-  this->y_low_ = row_low;
-  this->y_high_ = row_high;
-}
-
 bool HOT EPaperSSD1681::transfer_data() {
   if (this->current_data_index_ == 0 && this->send_red_) {
     if (!this->partial_) {
@@ -55,7 +15,6 @@ bool HOT EPaperSSD1681::transfer_data() {
       this->y_high_ = this->height_;
     } else {
       // 0x26 already holds the image on the panel: the controller copies 0x24 into it after each refresh
-      this->bounds_from_changes_();
       this->set_window();
       this->send_red_ = false;
     }

esphome/components/epaper_spi/epaper_spi_ssd1681.h

@@ -16,10 +16,6 @@ class EPaperSSD1681 : public EPaperSSD1683 {
   }
 
  protected:
-  // Reads the previous frame to compute the changed window for a partial refresh
-  bool needs_previous_frame() const override { return true; }
-  // Shrinks the update bounds to the bytes that differ from the frame last sent
-  void bounds_from_changes_();
   bool transfer_data() override;
   void refresh_screen(bool partial) override;
 };

esphome/components/epaper_spi/epaper_spi_ssd1683.cpp

@@ -71,15 +71,12 @@ bool HOT EPaperSSD1683::transfer_data() {
   ESP_LOGV(TAG, "Writing %u bytes at line %zu at %ums", row_length, this->current_data_index_, (unsigned) millis());
   this->start_data_();
   while (this->current_data_index_ != this->y_high_) {
-    const size_t row_start = this->current_data_index_ * this->row_width_ + this->x_low_;
-    size_t data_idx = row_start;
+    size_t data_idx = this->current_data_index_ * this->row_width_ + this->x_low_;
     for (size_t i = 0; i != row_length; i++) {
       bytes_to_send[i] = this->buffer_[data_idx++];
     }
     ++this->current_data_index_;
     this->write_array(&bytes_to_send.front(), row_length);  // NOLINT
-    if (!this->send_red_)
-      this->record_sent_(row_start, &bytes_to_send.front(), row_length);
     if (millis() - start_time > MAX_TRANSFER_TIME) {
       // Let the main loop run and come back next loop
       this->disable();

esphome/components/epaper_spi/epaper_spi_t133a01.cpp

@@ -232,7 +232,6 @@ void EPaperT133A01::fill(Color color) {
   }
   auto pixel_color = color_to_index(color);
   this->buffer_.fill(pixel_color + (pixel_color << 4));
-  this->drawn_since_hash_ = true;
 }
 
 void EPaperT133A01::draw_pixel_at(int x, int y, Color color) {

esphome/components/epaper_spi/epaper_waveshare_bwr.cpp

@@ -1,5 +1,4 @@
 #include "epaper_waveshare_bwr.h"
-#include "esphome/core/helpers.h"
 
 #include <algorithm>
 
@@ -37,9 +36,17 @@ void EPaperWaveshareBWR::draw_pixel_at(int x, int y, Color color) {
 
   const auto bwr = color_to_bwr(color);
 
-  assign_bits(this->buffer_[pos], bit, bwr == BwrState::BWR_BLACK);
+  if (bwr == BwrState::BWR_BLACK) {
+    this->buffer_[pos] |= bit;
+  } else {
+    this->buffer_[pos] &= ~bit;
+  }
 
-  assign_bits(this->buffer_[red_offset + pos], bit, bwr == BwrState::BWR_RED);
+  if (bwr == BwrState::BWR_RED) {
+    this->buffer_[red_offset + pos] |= bit;
+  } else {
+    this->buffer_[red_offset + pos] &= ~bit;
+  }
 }
 
 void EPaperWaveshareBWR::fill(Color color) {

esphome/components/es8156/es8156.cpp

@@ -1,7 +1,6 @@
 #include "es8156.h"
 #include "es8156_const.h"
 #include "esphome/core/hal.h"
-#include "esphome/core/helpers.h"
 #include "esphome/core/log.h"
 #include <cinttypes>
 
@@ -101,7 +100,11 @@ bool ES8156::set_mute_state_(bool mute_state) {
 
   ESP_LOGV(TAG, "Read ES8156_REG13_DAC_MUTE: %u", reg13);
 
-  assign_bits(reg13, BIT(1) | BIT(2), mute_state);
+  if (mute_state) {
+    reg13 |= BIT(1) | BIT(2);
+  } else {
+    reg13 &= ~(BIT(1) | BIT(2));
+  }
 
   ESP_LOGV(TAG, "Setting ES8156_REG13_DAC_MUTE to %u (muted: %s)", reg13, YESNO(mute_state));
   return this->write_byte(ES8156_REG13_DAC_MUTE, reg13);

esphome/components/es8311/es8311.cpp

@@ -1,7 +1,6 @@
 #include "es8311.h"
 #include "es8311_const.h"
 #include "esphome/core/hal.h"
-#include "esphome/core/helpers.h"
 #include "esphome/core/log.h"
 #include <cinttypes>
 
@@ -155,7 +154,11 @@ bool ES8311::configure_clock_() {
   // Register 0x06
   uint8_t reg06;
   ES8311_ERROR_CHECK(this->read_byte(ES8311_REG06_CLK_MANAGER, &reg06));
-  assign_bits(reg06, BIT(5), this->sclk_inverted_);
+  if (this->sclk_inverted_) {
+    reg06 |= BIT(5);
+  } else {
+    reg06 &= ~BIT(5);
+  }
   reg06 &= 0xE0;
   if (coefficient->bclk_div < 19) {
     reg06 |= (coefficient->bclk_div - 1) << 0;
@@ -220,7 +223,11 @@ bool ES8311::set_mute_state_(bool mute_state) {
     return false;
   }
 
-  assign_bits(reg31, BIT(6) | BIT(5), mute_state);
+  if (mute_state) {
+    reg31 |= BIT(6) | BIT(5);
+  } else {
+    reg31 &= ~(BIT(6) | BIT(5));
+  }
 
   return this->write_byte(ES8311_REG31_DAC, reg31);
 }

esphome/components/es8388/es8388.cpp

@@ -2,7 +2,6 @@
 
 #include <cinttypes>
 #include "esphome/core/hal.h"
-#include "esphome/core/helpers.h"
 #include "esphome/core/log.h"
 
 namespace esphome::es8388 {
@@ -185,7 +184,11 @@ bool ES8388::set_mute_state_(bool mute_state) {
   // DAC settings that must be preserved. Previously muting overwrote the whole
   // register with 0x3C and unmuting never cleared the bit, so once muted the DAC
   // could not be unmuted again.
-  assign_bits(value, ES8388_DACCONTROL3_DAC_MUTE, mute_state);
+  if (mute_state) {
+    value |= ES8388_DACCONTROL3_DAC_MUTE;
+  } else {
+    value &= ~ES8388_DACCONTROL3_DAC_MUTE;
+  }
 
   ESP_LOGV(TAG, "Setting ES8388_DACCONTROL3 to 0x%02X (muted: %s)", value, YESNO(mute_state));
   return this->write_byte(ES8388_DACCONTROL3, value);

esphome/components/gree/gree.cpp

@@ -1,6 +1,5 @@
 #include "gree.h"
 #include "esphome/components/remote_base/remote_base.h"
-#include "esphome/core/helpers.h"
 
 namespace esphome::gree {
 
@@ -25,7 +24,11 @@ void GreeClimate::set_model(Model model) {
 }
 
 void GreeClimate::set_mode_bit(uint8_t bit_mask, bool enabled) {
-  assign_bits(this->mode_bits_, bit_mask, enabled);
+  if (enabled) {
+    this->mode_bits_ |= bit_mask;
+  } else {
+    this->mode_bits_ &= ~bit_mask;
+  }
   this->transmit_state();
 }
 

esphome/components/hitachi_ac344/hitachi_ac344.cpp

@@ -1,5 +1,4 @@
 #include "hitachi_ac344.h"
-#include "esphome/core/helpers.h"
 
 namespace esphome::hitachi_ac344 {
 
@@ -17,6 +16,15 @@ void set_bits(uint8_t *const dst, const uint8_t offset, const uint8_t nbits, con
   *dst |= ((data & mask) << offset);
 }
 
+void set_bit(uint8_t *const data, const uint8_t position, const bool on) {
+  uint8_t mask = 1 << position;
+  if (on) {
+    *data |= mask;
+  } else {
+    *data &= ~mask;
+  }
+}
+
 uint8_t *invert_byte_pairs(uint8_t *ptr, const uint16_t length) {
   for (uint16_t i = 1; i < length; i += 2) {
     // Code done this way to avoid a compiler warning bug.
@@ -116,7 +124,7 @@ bool HitachiClimate::get_swing_v_toggle_() { return get_button_() == HITACHI_AC3
 
 void HitachiClimate::set_swing_v_(bool on) {
   set_swing_v_toggle_(on);  // Set the button value.
-  assign_bits(this->remote_state_[HITACHI_AC344_SWINGV_BYTE], 1 << HITACHI_AC344_SWINGV_OFFSET, on);
+  set_bit(&remote_state_[HITACHI_AC344_SWINGV_BYTE], HITACHI_AC344_SWINGV_OFFSET, on);
 }
 
 bool HitachiClimate::get_swing_v_() {

esphome/components/hitachi_ac424/hitachi_ac424.cpp

@@ -1,5 +1,4 @@
 #include "hitachi_ac424.h"
-#include "esphome/core/helpers.h"
 
 namespace esphome::hitachi_ac424 {
 
@@ -17,6 +16,15 @@ void set_bits(uint8_t *const dst, const uint8_t offset, const uint8_t nbits, con
   *dst |= ((data & mask) << offset);
 }
 
+void set_bit(uint8_t *const data, const uint8_t position, const bool on) {
+  uint8_t mask = 1 << position;
+  if (on) {
+    *data |= mask;
+  } else {
+    *data &= ~mask;
+  }
+}
+
 uint8_t *invert_byte_pairs(uint8_t *ptr, const uint16_t length) {
   for (uint16_t i = 1; i < length; i += 2) {
     // Code done this way to avoid a compiler warning bug.
@@ -116,7 +124,7 @@ bool HitachiClimate::get_swing_v_toggle_() { return get_button_() == HITACHI_AC4
 
 void HitachiClimate::set_swing_v_(bool on) {
   set_swing_v_toggle_(on);  // Set the button value.
-  assign_bits(this->remote_state_[HITACHI_AC424_SWINGV_BYTE], 1 << HITACHI_AC424_SWINGV_OFFSET, on);
+  set_bit(&remote_state_[HITACHI_AC424_SWINGV_BYTE], HITACHI_AC424_SWINGV_OFFSET, on);
 }
 
 bool HitachiClimate::get_swing_v_() {

esphome/components/max17043/max17043.cpp

@@ -3,36 +3,67 @@
 
 namespace esphome::max17043 {
 
-// MAX17043 is a 1-Cell Fuel Gauge with ModelGauge and Low-Battery Alert
+// MAX174043 is a 1-Cell Fuel Gauge with ModelGauge and Low-Battery Alert
 // Consult the datasheet at https://www.analog.com/en/products/max17043.html
 
 ESPHOME_LOG_TAG(TAG, "max17043");
 
-void MAX17043Component::update() {
-  if (!this->ready_for_update_())
-    return;
+static const uint8_t MAX17043_VCELL = 0x02;
+static const uint8_t MAX17043_SOC = 0x04;
+static const uint8_t MAX17043_CONFIG = 0x0c;
 
-  uint16_t raw;
-  bool ok = true;
+static const uint16_t MAX17043_CONFIG_POWER_UP_DEFAULT = 0x971C;
+static const uint16_t MAX17043_CONFIG_SAFE_MASK = 0xFF1F;  // mask out sleep bit (7), unused bit (6) and alert bit (4)
+static const uint16_t MAX17043_CONFIG_SLEEP_MASK = 0x0080;
+
+void MAX17043Component::update() {
+  uint16_t raw_voltage, raw_percent;
 
   if (this->voltage_sensor_ != nullptr) {
-    if (this->read_byte_16(max170xx::REG_VCELL, &raw)) {
-      // 12 bits in the top of the word at 1.25 mV
-      this->voltage_sensor_->publish_state((raw >> 4) * 1.25e-3f);
+    if (!this->read_byte_16(MAX17043_VCELL, &raw_voltage)) {
+      this->status_set_warning(LOG_STR("Unable to read MAX17043_VCELL"));
     } else {
-      ok = false;
+      float voltage = (1.25f * (float) (raw_voltage >> 4)) / 1000.0f;
+      this->voltage_sensor_->publish_state(voltage);
+      this->status_clear_warning();
     }
   }
   if (this->battery_remaining_sensor_ != nullptr) {
-    if (this->read_byte_16(max170xx::REG_SOC, &raw)) {
-      float percent = (float) ((raw >> 8) + 0.003906f * (raw & 0x00ff));
-      this->battery_remaining_sensor_->publish_state(percent);
+    if (!this->read_byte_16(MAX17043_SOC, &raw_percent)) {
+      this->status_set_warning(LOG_STR("Unable to read MAX17043_SOC"));
     } else {
-      ok = false;
+      float percent = (float) ((raw_percent >> 8) + 0.003906f * (raw_percent & 0x00ff));
+      this->battery_remaining_sensor_->publish_state(percent);
+      this->status_clear_warning();
     }
   }
+}
 
-  this->status_comm_result(ok, LOG_STR("Register read failed"));
+void MAX17043Component::setup() {
+  uint16_t config_reg;
+  if (this->write(&MAX17043_CONFIG, 1) != i2c::ERROR_OK) {
+    this->status_set_warning();
+    return;
+  }
+
+  if (this->read(reinterpret_cast<uint8_t *>(&config_reg), 2) != i2c::ERROR_OK) {
+    this->status_set_warning();
+    return;
+  }
+
+  config_reg = i2c::i2ctohs(config_reg) & MAX17043_CONFIG_SAFE_MASK;
+  ESP_LOGV(TAG, "MAX17043 CONFIG register reads 0x%X", config_reg);
+
+  if (config_reg != MAX17043_CONFIG_POWER_UP_DEFAULT) {
+    this->mark_failed(LOG_STR("Device does not appear to be a MAX17043"));
+    return;
+  }
+
+  // need to write back to config register to reset the sleep bit
+  if (!this->write_byte_16(MAX17043_CONFIG, MAX17043_CONFIG_POWER_UP_DEFAULT)) {
+    this->mark_failed(LOG_STR("sleep reset failed"));
+    return;
+  }
 }
 
 void MAX17043Component::dump_config() {
@@ -43,4 +74,13 @@ void MAX17043Component::dump_config() {
   LOG_SENSOR("  ", "Battery Level", this->battery_remaining_sensor_);
 }
 
+void MAX17043Component::sleep_mode() {
+  if (!this->is_failed()) {
+    if (!this->write_byte_16(MAX17043_CONFIG, MAX17043_CONFIG_POWER_UP_DEFAULT | MAX17043_CONFIG_SLEEP_MASK)) {
+      ESP_LOGW(TAG, "Unable to write the sleep bit to config register");
+      this->status_set_warning();
+    }
+  }
+}
+
 }  // namespace esphome::max17043

esphome/components/max17043/max17043.h

@@ -1,18 +1,21 @@
 #pragma once
 
-#include "esphome/components/max170xx/max170xx.h"
+#include "esphome/core/component.h"
 #include "esphome/components/sensor/sensor.h"
+#include "esphome/components/i2c/i2c.h"
 
 namespace esphome::max17043 {
 
-class MAX17043Component final : public max170xx::MAX170xxComponent<max170xx::Model::MODEL_MAX17043> {
+class MAX17043Component final : public PollingComponent, public i2c::I2CDevice {
  public:
+  void setup() override;
   void dump_config() override;
   void update() override;
+  void sleep_mode();
 
-  void set_voltage_sensor(sensor::Sensor *voltage_sensor) { this->voltage_sensor_ = voltage_sensor; }
+  void set_voltage_sensor(sensor::Sensor *voltage_sensor) { voltage_sensor_ = voltage_sensor; }
   void set_battery_remaining_sensor(sensor::Sensor *battery_remaining_sensor) {
-    this->battery_remaining_sensor_ = battery_remaining_sensor;
+    battery_remaining_sensor_ = battery_remaining_sensor;
   }
 
  protected:

esphome/components/max17043/sensor.py

@@ -16,7 +16,6 @@ from esphome.const import (
 )
 from esphome.types import ConfigType
 
-AUTO_LOAD = ["max170xx"]
 DEPENDENCIES = ["i2c"]
 
 max17043_ns = cg.esphome_ns.namespace("max17043")

esphome/components/max17048/__init__.py

@@ -1,2 +1,2 @@
-CODEOWNERS = ["@B48D81EFCC", "@ryansch"]
+CODEOWNERS = ["@B48D81EFCC"]
 DOMAIN = "max17048"

esphome/components/max17048/max17048.cpp

@@ -8,27 +8,41 @@ namespace esphome::max17048 {
 
 ESPHOME_LOG_TAG(TAG, "max17048");
 
-static constexpr uint8_t REG_CRATE = 0x16;  // charge rate, signed
+static constexpr uint8_t REG_VCELL = 0x02;    // cell voltage
+static constexpr uint8_t REG_SOC = 0x04;      // state of charge
+static constexpr uint8_t REG_VERSION = 0x08;  // 0x001x
+static constexpr uint8_t REG_CRATE = 0x16;    // charge rate, signed
+
+static constexpr uint16_t VERSION_MASK = 0xFFF0;
+static constexpr uint16_t VERSION_FAMILY = 0x0010;
 
 static constexpr float VCELL_VOLTS_PER_LSB = 78.125e-6f;
 static constexpr float SOC_PERCENT_PER_LSB = 1.0f / 256.0f;
 static constexpr float CRATE_PERCENT_PER_HOUR_PER_LSB = 0.208f;
 
-void MAX17048Component::update() {
-  if (!this->ready_for_update_())
+void MAX17048Component::setup() {
+  uint16_t version;
+  if (!this->read_byte_16(REG_VERSION, &version)) {
+    this->mark_failed(LOG_STR(ESP_LOG_MSG_COMM_FAIL));
     return;
+  }
+  if ((version & VERSION_MASK) != VERSION_FAMILY) {
+    ESP_LOGW(TAG, "Unexpected version 0x%04X", version);
+  }
+}
 
+void MAX17048Component::update() {
   bool ok = true;
   uint16_t raw;
   if (this->battery_voltage_sensor_ != nullptr) {
-    if (this->read_byte_16(max170xx::REG_VCELL, &raw)) {
+    if (this->read_byte_16(REG_VCELL, &raw)) {
       this->battery_voltage_sensor_->publish_state(raw * VCELL_VOLTS_PER_LSB);
     } else {
       ok = false;
     }
   }
   if (this->battery_level_sensor_ != nullptr) {
-    if (this->read_byte_16(max170xx::REG_SOC, &raw)) {
+    if (this->read_byte_16(REG_SOC, &raw)) {
       this->battery_level_sensor_->publish_state(raw * SOC_PERCENT_PER_LSB);
     } else {
       ok = false;

esphome/components/max17048/max17048.h

@@ -1,16 +1,18 @@
 #pragma once
 
-#include "esphome/components/max170xx/max170xx.h"
+#include "esphome/core/component.h"
 #include "esphome/components/sensor/sensor.h"
+#include "esphome/components/i2c/i2c.h"
 
 namespace esphome::max17048 {
 
-class MAX17048Component final : public max170xx::MAX170xxComponent<max170xx::Model::MODEL_MAX17048> {
+class MAX17048Component final : public PollingComponent, public i2c::I2CDevice {
   SUB_SENSOR(battery_voltage)
   SUB_SENSOR(battery_level)
   SUB_SENSOR(rate)
 
  public:
+  void setup() override;
   void dump_config() override;
   void update() override;
 };

esphome/components/max17048/sensor.py

@@ -1,12 +1,9 @@
-from esphome import automation
-from esphome.automation import maybe_simple_id
 import esphome.codegen as cg
 from esphome.components import i2c, sensor
 import esphome.config_validation as cv
 from esphome.const import (
     CONF_BATTERY_LEVEL,
     CONF_BATTERY_VOLTAGE,
-    CONF_ID,
     CONF_RATE,
     DEVICE_CLASS_BATTERY,
     DEVICE_CLASS_VOLTAGE,
@@ -17,7 +14,6 @@ from esphome.const import (
 )
 from esphome.types import ConfigType
 
-AUTO_LOAD = ["max170xx"]
 DEPENDENCIES = ["i2c"]
 
 UNIT_PERCENT_PER_HOUR = "%/h"
@@ -65,15 +61,3 @@ async def to_code(config: ConfigType) -> None:
     await sensors(CONF_BATTERY_VOLTAGE, var.set_battery_voltage_sensor)
     await sensors(CONF_BATTERY_LEVEL, var.set_battery_level_sensor)
     await sensors(CONF_RATE, var.set_rate_sensor)
-
-
-MAX17048_ACTION_SCHEMA = maybe_simple_id(
-    {
-        cv.Required(CONF_ID): cv.use_id(MAX17048Component),
-    }
-)
-
-
-automation.register_apply_action(
-    "max17048.sleep_mode", MAX17048_ACTION_SCHEMA, automation.ApplyCall("sleep_mode()")
-)

esphome/components/max170xx/__init__.py

@@ -1,3 +0,0 @@
-CODEOWNERS = ["@ryansch"]
-DEPENDENCIES = ["i2c"]
-DOMAIN = "max170xx"

esphome/components/max170xx/max170xx.cpp

@@ -1,87 +0,0 @@
-#include "max170xx.h"
-#include "esphome/core/log.h"
-
-namespace esphome::max170xx {
-
-ESPHOME_LOG_TAG(TAG, "max170xx");
-
-template<Model MODEL> void MAX170xxComponent<MODEL>::setup() {
-  // A silent bus is retried from update(): some boards gate the I2C rail until after setup.
-  // An early on_boot may already have configured the gauge and put it to sleep, so this must not configure again.
-  this->ready_for_update_();
-}
-
-template<Model MODEL> bool MAX170xxComponent<MODEL>::ready_for_update_() {
-  if (this->configured_ || this->configure_())
-    return true;
-  this->status_set_warning(LOG_STR("Gauge did not answer"));
-  return false;
-}
-
-template<Model MODEL> bool MAX170xxComponent<MODEL>::configure_() {
-  uint16_t config;
-  if (!this->read_byte_16(REG_CONFIG, &config))
-    return false;
-
-  const bool was_asleep = (config & CONFIG_SLEEP) != 0;
-  // RCOMP and ATHD survive on the battery, so an earlier firmware's values are reset here, not treated as a fault
-  if ((config & CONFIG_SAFE_MASK) != CONFIG_POWER_UP_DEFAULT) {
-    ESP_LOGW(TAG, "CONFIG reads 0x%04X, expected 0x%04X; resetting it", config & CONFIG_SAFE_MASK,
-             CONFIG_POWER_UP_DEFAULT);
-  }
-
-  uint16_t version;
-  if (this->read_byte_16(REG_VERSION, &version)) {
-    ESP_LOGCONFIG(TAG, "IC version: 0x%04X", version);
-  }
-
-  // Write back the power-up value to clear a stale sleep bit; a failed write is retried like a silent bus
-  if (!this->write_byte_16(REG_CONFIG, CONFIG_POWER_UP_DEFAULT))
-    return false;
-
-  this->configured_ = true;
-  // Waking from sleep raises a false low-battery alert; a real one at an ordinary boot is left alone
-  if (was_asleep)
-    this->set_timeout(WAKE_ALERT_CLEAR_TIMEOUT_ID, WAKE_ALERT_CLEAR_DELAY_MS, [this]() { this->clear_wake_alert_(); });
-  return true;
-}
-
-template<Model MODEL> void MAX170xxComponent<MODEL>::clear_wake_alert_() {
-  uint16_t config;
-  if (!this->read_byte_16(REG_CONFIG, &config) || !this->write_byte_16(REG_CONFIG, config & ~CONFIG_ALRT)) {
-    this->status_set_warning(LOG_STR("Wake alert clear failed"));
-    return;
-  }
-  if constexpr (MODEL == Model::MODEL_MAX17048) {
-    uint16_t status;
-    if (!this->read_byte_16(REG_STATUS, &status) || !this->write_byte_16(REG_STATUS, status & ~STATUS_HD))
-      this->status_set_warning(LOG_STR("Wake alert clear failed"));
-  }
-}
-
-template<Model MODEL> void MAX170xxComponent<MODEL>::sleep_mode() {
-  if (this->is_failed())
-    return;
-  // The deferred configuration clears the sleep bit, so it has to run before the gauge is put to sleep
-  if (!this->ready_for_update_())
-    return;
-
-  // A clear still pending would otherwise run against a sleeping gauge
-  if (this->cancel_timeout(WAKE_ALERT_CLEAR_TIMEOUT_ID))
-    this->clear_wake_alert_();
-
-  if constexpr (MODEL == Model::MODEL_MAX17048) {
-    if (!this->write_byte_16(REG_MODE, MODE_EN_SLEEP)) {
-      this->status_set_warning(LOG_STR("Unable to enable sleep mode in the mode register"));
-      return;
-    }
-  }
-
-  if (!this->write_byte_16(REG_CONFIG, CONFIG_POWER_UP_DEFAULT | CONFIG_SLEEP))
-    this->status_set_warning(LOG_STR("Unable to write the sleep bit to config register"));
-}
-
-template class MAX170xxComponent<Model::MODEL_MAX17043>;
-template class MAX170xxComponent<Model::MODEL_MAX17048>;
-
-}  // namespace esphome::max170xx

esphome/components/max170xx/max170xx.h

@@ -1,61 +0,0 @@
-#pragma once
-
-#include "esphome/core/component.h"
-#include "esphome/components/i2c/i2c.h"
-
-namespace esphome::max170xx {
-
-// Shared base for the ModelGauge fuel gauges.
-// MAX17043: https://www.analog.com/en/products/max17043.html
-// MAX17048: https://www.analog.com/en/products/max17048.html
-// The MAX17048 is register-compatible with the MAX17043, and adds a STATUS register and a MODE.EnSleep gate in
-// front of CONFIG.SLEEP.
-
-static constexpr uint8_t REG_VCELL = 0x02;
-static constexpr uint8_t REG_SOC = 0x04;
-static constexpr uint8_t REG_MODE = 0x06;
-static constexpr uint8_t REG_VERSION = 0x08;
-static constexpr uint8_t REG_CONFIG = 0x0C;
-static constexpr uint8_t REG_STATUS = 0x1A;
-
-static constexpr uint16_t CONFIG_POWER_UP_DEFAULT = 0x971C;
-// Mask out SLEEP (7), ALRT (5), and bit 6, which is a don't-care on the MAX17043 but ALSC on the MAX17048.
-static constexpr uint16_t CONFIG_SAFE_MASK = 0xFF1F;
-static constexpr uint16_t CONFIG_SLEEP = 0x0080;
-static constexpr uint16_t CONFIG_ALRT = 0x0020;
-
-// CONFIG.SLEEP is ignored unless MODE.EnSleep (bit 13) is set first.
-static constexpr uint16_t MODE_EN_SLEEP = 0x2000;
-static constexpr uint16_t STATUS_HD = 0x1000;
-
-static constexpr uint32_t WAKE_ALERT_CLEAR_TIMEOUT_ID = 0;
-// The gauge raises its false wake alert some time after the wake write; on hardware it rose 0.8 to 1.0 s later
-static constexpr uint32_t WAKE_ALERT_CLEAR_DELAY_MS = 2000;
-
-enum class Model : uint8_t {
-  MODEL_MAX17043,
-  MODEL_MAX17048,
-};
-
-/// Defined in max170xx.cpp, which instantiates both models.
-template<Model MODEL> class MAX170xxComponent : public PollingComponent, public i2c::I2CDevice {
- public:
-  void setup() override;
-  void sleep_mode();
-
- protected:
-  /// True once the gauge is configured; otherwise retries the configuration and warns if the gauge did not answer.
-  /// Call first in update().
-  bool ready_for_update_();
-  /// Verify and wake the gauge; false if it did not answer.
-  bool configure_();
-  /// Clear the false alert raised on waking, leaving every other CONFIG and STATUS bit as it is.
-  void clear_wake_alert_();
-
-  bool configured_{false};
-};
-
-extern template class MAX170xxComponent<Model::MODEL_MAX17043>;
-extern template class MAX170xxComponent<Model::MODEL_MAX17048>;
-
-}  // namespace esphome::max170xx

esphome/components/mcp23016/mcp23016.cpp

@@ -1,5 +1,4 @@
 #include "mcp23016.h"
-#include "esphome/core/helpers.h"
 #include "esphome/core/log.h"
 #include <cstdio>
 
@@ -80,7 +79,11 @@ void MCP23016::update_reg_(uint8_t pin, bool pin_value, uint8_t reg_addr) {
     this->read_reg_(reg_addr, &reg_value);
   }
 
-  assign_bits(reg_value, 1 << pin, pin_value);
+  if (pin_value) {
+    reg_value |= 1 << pin;
+  } else {
+    reg_value &= ~(1 << pin);
+  }
 
   this->write_reg_(reg_addr, reg_value);
 

esphome/components/mcp23x08_base/mcp23x08_base.cpp

@@ -1,5 +1,4 @@
 #include "mcp23x08_base.h"
-#include "esphome/core/helpers.h"
 #include "esphome/core/log.h"
 
 namespace esphome::mcp23x08_base {
@@ -79,7 +78,11 @@ void MCP23X08Base::update_reg(uint8_t pin, bool pin_value, uint8_t reg_addr) {
     this->read_reg(reg_addr, &reg_value);
   }
 
-  assign_bits(reg_value, 1 << bit, pin_value);
+  if (pin_value) {
+    reg_value |= 1 << bit;
+  } else {
+    reg_value &= ~(1 << bit);
+  }
 
   this->write_reg(reg_addr, reg_value);
 

esphome/components/mcp23x17_base/mcp23x17_base.cpp

@@ -92,7 +92,11 @@ void MCP23X17Base::update_reg(uint8_t pin, bool pin_value, uint8_t reg_addr) {
     this->read_reg(reg_addr, &reg_value);
   }
 
-  assign_bits(reg_value, 1 << bit, pin_value);
+  if (pin_value) {
+    reg_value |= 1 << bit;
+  } else {
+    reg_value &= ~(1 << bit);
+  }
 
   this->write_reg(reg_addr, reg_value);
 

esphome/components/opentherm/hub.cpp

@@ -33,22 +33,22 @@ uint16_t parse_u8_hb_60(OpenthermData &data) { return data.valueHB * 60; }
 int16_t parse_s16(OpenthermData &data) { return data.get_s16(); }
 float parse_f88(OpenthermData &data) { return data.get_f88(); }
 
-void write_flag8_lb_0(const bool value, OpenthermData &data) { assign_bits(data.valueLB, 1 << 0, value); }
-void write_flag8_lb_1(const bool value, OpenthermData &data) { assign_bits(data.valueLB, 1 << 1, value); }
-void write_flag8_lb_2(const bool value, OpenthermData &data) { assign_bits(data.valueLB, 1 << 2, value); }
-void write_flag8_lb_3(const bool value, OpenthermData &data) { assign_bits(data.valueLB, 1 << 3, value); }
-void write_flag8_lb_4(const bool value, OpenthermData &data) { assign_bits(data.valueLB, 1 << 4, value); }
-void write_flag8_lb_5(const bool value, OpenthermData &data) { assign_bits(data.valueLB, 1 << 5, value); }
-void write_flag8_lb_6(const bool value, OpenthermData &data) { assign_bits(data.valueLB, 1 << 6, value); }
-void write_flag8_lb_7(const bool value, OpenthermData &data) { assign_bits(data.valueLB, 1 << 7, value); }
-void write_flag8_hb_0(const bool value, OpenthermData &data) { assign_bits(data.valueHB, 1 << 0, value); }
-void write_flag8_hb_1(const bool value, OpenthermData &data) { assign_bits(data.valueHB, 1 << 1, value); }
-void write_flag8_hb_2(const bool value, OpenthermData &data) { assign_bits(data.valueHB, 1 << 2, value); }
-void write_flag8_hb_3(const bool value, OpenthermData &data) { assign_bits(data.valueHB, 1 << 3, value); }
-void write_flag8_hb_4(const bool value, OpenthermData &data) { assign_bits(data.valueHB, 1 << 4, value); }
-void write_flag8_hb_5(const bool value, OpenthermData &data) { assign_bits(data.valueHB, 1 << 5, value); }
-void write_flag8_hb_6(const bool value, OpenthermData &data) { assign_bits(data.valueHB, 1 << 6, value); }
-void write_flag8_hb_7(const bool value, OpenthermData &data) { assign_bits(data.valueHB, 1 << 7, value); }
+void write_flag8_lb_0(const bool value, OpenthermData &data) { data.valueLB = write_bit(data.valueLB, 0, value); }
+void write_flag8_lb_1(const bool value, OpenthermData &data) { data.valueLB = write_bit(data.valueLB, 1, value); }
+void write_flag8_lb_2(const bool value, OpenthermData &data) { data.valueLB = write_bit(data.valueLB, 2, value); }
+void write_flag8_lb_3(const bool value, OpenthermData &data) { data.valueLB = write_bit(data.valueLB, 3, value); }
+void write_flag8_lb_4(const bool value, OpenthermData &data) { data.valueLB = write_bit(data.valueLB, 4, value); }
+void write_flag8_lb_5(const bool value, OpenthermData &data) { data.valueLB = write_bit(data.valueLB, 5, value); }
+void write_flag8_lb_6(const bool value, OpenthermData &data) { data.valueLB = write_bit(data.valueLB, 6, value); }
+void write_flag8_lb_7(const bool value, OpenthermData &data) { data.valueLB = write_bit(data.valueLB, 7, value); }
+void write_flag8_hb_0(const bool value, OpenthermData &data) { data.valueHB = write_bit(data.valueHB, 0, value); }
+void write_flag8_hb_1(const bool value, OpenthermData &data) { data.valueHB = write_bit(data.valueHB, 1, value); }
+void write_flag8_hb_2(const bool value, OpenthermData &data) { data.valueHB = write_bit(data.valueHB, 2, value); }
+void write_flag8_hb_3(const bool value, OpenthermData &data) { data.valueHB = write_bit(data.valueHB, 3, value); }
+void write_flag8_hb_4(const bool value, OpenthermData &data) { data.valueHB = write_bit(data.valueHB, 4, value); }
+void write_flag8_hb_5(const bool value, OpenthermData &data) { data.valueHB = write_bit(data.valueHB, 5, value); }
+void write_flag8_hb_6(const bool value, OpenthermData &data) { data.valueHB = write_bit(data.valueHB, 6, value); }
+void write_flag8_hb_7(const bool value, OpenthermData &data) { data.valueHB = write_bit(data.valueHB, 7, value); }
 void write_u8_lb(const uint8_t value, OpenthermData &data) { data.valueLB = value; }
 void write_u8_hb(const uint8_t value, OpenthermData &data) { data.valueHB = value; }
 void write_s8_lb(const int8_t value, OpenthermData &data) { data.valueLB = (uint8_t) value; }

esphome/components/opentherm/opentherm.h

@@ -20,6 +20,14 @@ namespace esphome::opentherm {
 
 template<class T> constexpr T read_bit(T value, uint8_t bit) { return (value >> bit) & 0x01; }
 
+template<class T> constexpr T set_bit(T value, uint8_t bit) { return value |= (1UL << bit); }
+
+template<class T> constexpr T clear_bit(T value, uint8_t bit) { return value &= ~(1UL << bit); }
+
+template<class T> constexpr T write_bit(T value, uint8_t bit, uint8_t bit_value) {
+  return bit_value ? set_bit(value, bit) : clear_bit(value, bit);
+}
+
 enum OperationMode {
   IDLE = 0,  // no operation
 

esphome/components/packet_interface/__init__.py

@@ -1,56 +1,175 @@
+from collections.abc import Callable
+import importlib
+import pkgutil
 from typing import Any
 
 import esphome.codegen as cg
 from esphome.components.const import CONF_MAX_PACKET_SIZE
 import esphome.config_validation as cv
 from esphome.const import CONF_ID
+from esphome.core import ID
 from esphome.cpp_generator import MockObj, MockObjClass
+import esphome.final_validate as fv
 from esphome.types import ConfigType
 
+from . import layers
+from .layers import (
+    ADDRESSING,
+    BROADCAST_ADDRESS,
+    CONF_ADDRESSING,
+    CONF_DESTINATION,
+    CONF_PEERS,
+    STACK_ORDER,
+    PacketInterface,
+    build_stack,
+    check_packet_sizes,
+    check_session,
+    check_single_peer,
+    packet_interface_ns,
+    stack_auto_load,
+    stack_schema,
+)
+
 CODEOWNERS = ["@clydebarrow"]
 DOMAIN = "packet_interface"
 IS_PLATFORM_COMPONENT = True
 
 CONF_PACKET_INTERFACE = "packet_interface"
 
-packet_interface_ns = cg.esphome_ns.namespace("packet_interface")
-PacketInterface = packet_interface_ns.class_("PacketInterface", cg.Component)
+# Each module in layers registers a layer type; import them all before building the schemas from the registry
+for module_info in pkgutil.iter_modules(layers.__path__):
+    importlib.import_module(f".layers.{module_info.name}", package=__package__)
+
+LINK_LAYER_SCHEMAS = {
+    cv.Optional(CONF_ADDRESSING): ADDRESSING.schema(),
+    **stack_schema(),
+}
 
 __all__ = [
     "CONF_MAX_PACKET_SIZE",
     "CONF_PACKET_INTERFACE",
+    "interface_layers",
     "PacketInterface",
+    "final_validate_interface",
     "new_packet_interface",
     "packet_interface_ns",
     "packet_interface_schema",
 ]
 
 
+def AUTO_LOAD(config: list[ConfigType] | None = None) -> list[str]:
+    """Load only what the configured layers use, on the link and in each addressing peer.
+
+    Without a config, as tooling that lists dependencies calls it, everything a layer could load.
+    """
+    if config is None:
+        return ["binary_sensor", "xxtea"]
+    loads: set[str] = set()
+    for interface in config:
+        loads |= stack_auto_load(interface)
+        for peer in interface.get(CONF_ADDRESSING, {}).get(CONF_PEERS, []):
+            loads |= stack_auto_load(peer)
+    return sorted(loads)
+
+
+def _validate_layers(config: ConfigType) -> ConfigType:
+    """With peers, the layers go in each peer; otherwise check them against the one destination."""
+    check_session(config)
+    size = config[CONF_MAX_PACKET_SIZE]
+    if (addressing := config.get(CONF_ADDRESSING)) is None:
+        check_packet_sizes(config, size)
+        return config
+    size = ADDRESSING.get_type(addressing).packet_size(addressing, size)
+    if CONF_PEERS in addressing:
+        for kind in STACK_ORDER:
+            if kind.key in config:
+                raise cv.Invalid(
+                    f"With '{CONF_PEERS}', '{kind.key}' goes in each peer",
+                    path=[kind.key],
+                )
+        for index, peer in enumerate(addressing[CONF_PEERS]):
+            try:
+                check_packet_sizes(peer, size)
+            except cv.Invalid as err:
+                err.prepend([CONF_ADDRESSING, CONF_PEERS, index])
+                raise
+        return config
+    addressing.setdefault(CONF_DESTINATION, BROADCAST_ADDRESS)
+    check_single_peer(config, addressing[CONF_DESTINATION])
+    check_packet_sizes(config, size)
+    return config
+
+
+def interface_layers(interface_id: ID) -> ConfigType | None:
+    """During final validation, the configuration holding the layers of the packet interface with this id.
+
+    The id is a link's, or an addressing peer's.
+    """
+    for interface in fv.full_config.get().get(DOMAIN, []):
+        if interface[CONF_ID].id == interface_id.id:
+            return interface
+        for peer in interface.get(CONF_ADDRESSING, {}).get(CONF_PEERS, []):
+            if peer[CONF_ID].id == interface_id.id:
+                return peer
+    return None
+
+
+def final_validate_interface(key: str) -> Callable[[ConfigType], ConfigType]:
+    """Final validation for an application: a link with peers must be used through one of the peers."""
+
+    def validator(config: ConfigType) -> ConfigType:
+        interface_id: ID = config[key]
+        interface = interface_layers(interface_id)
+        if interface is not None and (
+            peers := interface.get(CONF_ADDRESSING, {}).get(CONF_PEERS)
+        ):
+            raise cv.Invalid(
+                f"'{interface_id.id}' has peers, so use the id of one of them, such as '{peers[0][CONF_ID].id}'",
+                path=[key],
+            )
+        return config
+
+    return validator
+
+
 def packet_interface_schema(
     class_: MockObjClass,
     default_max_packet_size: int,
     max_packet_size_limit: int = 4096,
 ) -> cv.Schema:
-    """Schema for a link platform."""
-    return cv.Schema(
-        {
-            cv.GenerateID(): cv.declare_id(class_),
-            cv.Optional(
-                CONF_MAX_PACKET_SIZE, default=default_max_packet_size
-            ): cv.int_range(16, max_packet_size_limit),
-        }
-    ).extend(cv.COMPONENT_SCHEMA)
+    """Schema for a link platform, with the layers that can be stacked on it."""
+    return (
+        cv.Schema(
+            {
+                cv.GenerateID(): cv.declare_id(class_),
+                cv.Optional(
+                    CONF_MAX_PACKET_SIZE, default=default_max_packet_size
+                ): cv.int_range(16, max_packet_size_limit),
+                **LINK_LAYER_SCHEMAS,
+            }
+        )
+        .extend(cv.COMPONENT_SCHEMA)
+        .add_extra(_validate_layers)
+    )
 
 
 async def new_packet_interface(config: ConfigType, *args: Any) -> MockObj:
-    """Create the link layer.
+    """Create the link layer and the layers configured on it, from the bottom up.
 
     The link's constructor takes its maximum packet size, usually as a std::span over a buffer that code generation
     sized from the configuration, so the two cannot differ.
 
-    Returns the link layer; applications reach the top layer with PacketInterface::top().
+    Returns the link layer; applications reach the top layer with PacketInterface::top(). With several addressing
+    peers, applications use the peers' ids instead.
     """
     var = cg.new_Pvariable(config[CONF_ID], *args)
     cg.add(var.set_name(config[CONF_ID].id))
     await cg.register_component(var, config)
+    if (addressing := config.get(CONF_ADDRESSING)) is None:
+        await build_stack(config, var)
+        return var
+    for port, layers_config in await ADDRESSING.get_type(addressing).build(
+        addressing, var
+    ):
+        await build_stack(config if layers_config is None else layers_config, port)
     return var

esphome/components/packet_interface/basic_addressing.cpp

@@ -0,0 +1,97 @@
+#include "basic_addressing.h"
+#ifdef USE_PACKET_INTERFACE_BASIC_ADDRESSING
+#include "esphome/core/log.h"
+
+namespace esphome::packet_interface {
+
+ESPHOME_LOG_TAG(TAG, "packet_interface.addressing");
+
+void BasicAddressing::setup() {
+  this->link_->add_packet_interface_listener(
+      [this](const PacketBuffer &data, const PacketMetaData &meta_data) { this->receive_(data, meta_data); });
+}
+
+void BasicAddressing::dump_config() {
+  ESP_LOGCONFIG(TAG,
+                "Basic Addressing on '%s':\n"
+                "  Address: 0x%04X",
+                this->link_->get_name(), this->address_);
+}
+
+bool BasicAddressing::send(const PacketBuffer &data, const PacketMetaData &meta_data, uint16_t destination) {
+  if (meta_data.destination_address != 0)
+    destination = meta_data.destination_address;
+  uint8_t header[HEADER_SIZE] = {static_cast<uint8_t>(destination), static_cast<uint8_t>(destination >> 8),
+                                 static_cast<uint8_t>(this->address_), static_cast<uint8_t>(this->address_ >> 8)};
+  PacketBuffer packet(header, HEADER_SIZE, &data, nullptr, 0);
+  return this->link_->send_to_interface(packet, meta_data);
+}
+
+void BasicAddressing::receive_(const PacketBuffer &data, const PacketMetaData &meta_data) {
+  // Lower layers deliver packets in one piece; the payload is passed up without copying
+  if (!data.is_contiguous()) {
+    ESP_LOGW(TAG, "%s: Packet split across buffers is not supported", this->link_->get_name());
+    return;
+  }
+  auto packet = data.as_span();
+  if (packet.size() < HEADER_SIZE) {
+    ESP_LOGV(TAG, "%s: Packet of %zu bytes is shorter than the address header, dropped", this->link_->get_name(),
+             packet.size());
+    return;
+  }
+  uint16_t destination = encode_uint16(packet[1], packet[0]);
+  uint16_t source = encode_uint16(packet[3], packet[2]);
+  if (source == this->address_ || (destination != this->address_ && destination != BROADCAST_ADDRESS))
+    return;
+  AddressingPort *source_port = nullptr;
+  AddressingPort *broadcast_port = nullptr;
+  for (auto *port : this->ports_) {
+    if (port->destination_ == source) {
+      source_port = port;
+    } else if (port->destination_ == BROADCAST_ADDRESS) {
+      broadcast_port = port;
+    }
+  }
+  // A broadcast goes to the broadcast port, even from a device with a port of its own, as that port's layers expect
+  // only its point-to-point packets; anything else goes to the source's port, or to the broadcast port if it has none
+  AddressingPort *target = source_port;
+  if (broadcast_port != nullptr && (destination == BROADCAST_ADDRESS || source_port == nullptr))
+    target = broadcast_port;
+  if (target == nullptr) {
+    ESP_LOGV(TAG, "%s: Packet from 0x%04X dropped", this->link_->get_name(), source);
+    return;
+  }
+  PacketMetaData received = meta_data;
+  received.source_address = source;
+  received.destination_address = destination;
+  target->on_receive_from_interface_(PacketBuffer(packet.data() + HEADER_SIZE, packet.size() - HEADER_SIZE), received);
+}
+
+AddressingPort::AddressingPort(BasicAddressing *addressing, uint16_t destination, bool only_port)
+    : PacketInterface(
+          remaining_packet_size(addressing->get_link()->get_max_packet_size(), BasicAddressing::HEADER_SIZE)),
+      addressing_(addressing),
+      destination_(destination) {
+  if (only_port) {
+    this->stack_on_(addressing->get_link(), CAPABILITY_ADDRESSING);
+  } else {
+    this->inherit_from_(addressing->get_link(), CAPABILITY_ADDRESSING);
+  }
+  // A link with no room leaves the layers above none either, so they fail their setup
+  addressing->add_port(this);
+}
+
+void AddressingPort::dump_config() {
+  ESP_LOGCONFIG(TAG,
+                "Addressing Port '%s':\n"
+                "  Max Packet Size: %zu",
+                this->name_, this->max_packet_size_);
+  if (this->destination_ == BasicAddressing::BROADCAST_ADDRESS) {
+    ESP_LOGCONFIG(TAG, "  Destination: broadcast");
+  } else {
+    ESP_LOGCONFIG(TAG, "  Destination: 0x%04X", this->destination_);
+  }
+}
+
+}  // namespace esphome::packet_interface
+#endif

esphome/components/packet_interface/basic_addressing.h

@@ -0,0 +1,69 @@
+#pragma once
+
+#include "esphome/core/defines.h"
+#ifdef USE_PACKET_INTERFACE_BASIC_ADDRESSING
+#include "esphome/core/helpers.h"
+#include "packet_interface.h"
+
+namespace esphome::packet_interface {
+
+class AddressingPort;
+
+/**
+ * An addressing layer for channels shared by several devices, such as an RS485 bus or a LoRa radio.
+ *
+ * Each packet starts with a 16-bit destination address and a 16-bit source address, little endian.
+ * BROADCAST_ADDRESS sends to every device. A packet is dropped unless it is addressed to this device or broadcast, and
+ * a packet from this device's own address, such as an echo on a half-duplex bus, is dropped too.
+ *
+ * Above this layer are one or more ports, each the bottom of its own stack of layers. A port with a destination
+ * address is a point-to-point link to that device: it sends to it and receives only its packets, so the reliability
+ * and session layers and the rolling code, which work between two devices only, can be used above it. A port with
+ * the broadcast destination sends to every device, and receives every broadcast, as well as packets from devices
+ * that have no port of their own. Without a broadcast port, a device's broadcasts go to its own port.
+ */
+class BasicAddressing : public Component {
+ public:
+  static constexpr uint16_t BROADCAST_ADDRESS = 0xFFFF;
+  /// Destination and source addresses.
+  static constexpr size_t HEADER_SIZE = 4;
+
+  BasicAddressing(PacketInterface *link, uint16_t address) : link_(link), address_(address) {}
+
+  void setup() override;
+  void dump_config() override;
+
+  PacketInterface *get_link() const { return this->link_; }
+  void add_port(AddressingPort *port) { this->ports_.push_back(port); }
+  /// Sends \p data to \p destination, or to the destination in \p meta_data if set.
+  bool send(const PacketBuffer &data, const PacketMetaData &meta_data, uint16_t destination);
+
+ protected:
+  void receive_(const PacketBuffer &data, const PacketMetaData &meta_data);
+
+  PacketInterface *link_;
+  const uint16_t address_;
+  StaticVector<AddressingPort *, PACKET_INTERFACE_ADDRESSING_PORT_COUNT> ports_;
+};
+
+/// The bottom of the stack of layers for one destination, or for broadcast, on an addressed channel.
+class AddressingPort : public PacketInterface {
+ public:
+  /// With \p only_port, the port is the top of the link, so top() on the link reaches this port's stack.
+  AddressingPort(BasicAddressing *addressing, uint16_t destination, bool only_port);
+
+  void dump_config() override;
+  bool send_to_interface(const PacketBuffer &data, const PacketMetaData &meta_data) override {
+    return this->addressing_->send(data, meta_data, this->destination_);
+  }
+  uint16_t get_destination() const { return this->destination_; }
+
+ protected:
+  friend class BasicAddressing;
+
+  BasicAddressing *addressing_;
+  const uint16_t destination_;
+};
+
+}  // namespace esphome::packet_interface
+#endif

esphome/components/packet_interface/basic_fragmentation.cpp

@@ -0,0 +1,160 @@
+#include "basic_fragmentation.h"
+#ifdef USE_PACKET_INTERFACE_BASIC_FRAGMENTATION
+#include <algorithm>
+#include <cstring>
+#include "esphome/core/helpers.h"
+#include "esphome/core/log.h"
+
+namespace esphome::packet_interface {
+
+ESPHOME_LOG_TAG(TAG, "packet_interface.fragmentation");
+
+static constexpr uint8_t LAST_FRAGMENT = 0x80;
+static constexpr uint8_t INDEX_MASK = 0x7F;
+
+BasicFragmentation::BasicFragmentation(PacketInterface *lower, size_t max_packet_size)
+    : PacketInterface(max_packet_size), lower_(lower) {
+  this->stack_on_(lower, CAPABILITY_FRAGMENTATION);
+}
+
+size_t BasicFragmentation::fragments_for_(size_t size) const {
+  size_t fragment_size = this->fragment_size_();
+  if (fragment_size == 0)
+    return SIZE_MAX;
+  return std::max<size_t>(1, (size + fragment_size - 1) / fragment_size);
+}
+
+void BasicFragmentation::setup() {
+  if (this->fragment_size_() == 0) {
+    this->mark_failed(LOG_STR("max_packet_size too small for the configured layers"));
+    return;
+  }
+  if (this->fragments_for_(this->max_packet_size_) > MAX_FRAGMENTS) {
+    this->mark_failed(LOG_STR("max_packet_size needs more than 128 fragments"));
+    return;
+  }
+  // Checked now, while the layer below holds nothing; a failed layer below reports its own failure instead
+  this->queue_too_short_ =
+      !this->lower_->is_failed() && this->fragments_for_(this->max_packet_size_) > this->lower_->get_send_capacity();
+  RAMAllocator<uint8_t> allocator;
+  this->tx_buffer_ = allocator.allocate(this->fragment_size_() + this->max_packet_size_);
+  if (this->tx_buffer_ == nullptr) {
+    this->mark_failed(LOG_STR("Not enough memory for the packet buffers"));
+    return;
+  }
+  this->rx_buffer_ = this->tx_buffer_ + this->fragment_size_();
+  // Numbering from a random start makes it unlikely that a packet joins fragments from before a restart
+  this->tx_number_ = random_uint32();
+  this->lower_->add_packet_interface_listener(
+      [this](const PacketBuffer &data, const PacketMetaData &meta_data) { this->receive_(data, meta_data); });
+}
+
+void BasicFragmentation::dump_config() {
+  // A link with no room for fragments fails setup, which core reports below
+  size_t fragments = this->fragment_size_() == 0 ? 0 : this->fragments_for_(this->max_packet_size_);
+  ESP_LOGCONFIG(TAG,
+                "Basic Fragmentation on '%s':\n"
+                "  Max Packet Size: %zu\n"
+                "  Fragment Size: %zu\n"
+                "  Fragments in the Largest Packet: %zu",
+                this->name_, this->max_packet_size_, this->fragment_size_(), fragments);
+  if (this->queue_too_short_) {
+    ESP_LOGW(TAG, "  The reliability queue is too short for the largest packets, which cannot be sent");
+  }
+}
+
+bool BasicFragmentation::send_to_interface(const PacketBuffer &data, const PacketMetaData &meta_data) {
+  if (this->tx_buffer_ == nullptr)
+    return false;
+  size_t size = data.size();
+  if (size > this->max_packet_size_) {
+    ESP_LOGW(TAG, "%s: Packet of %zu bytes is larger than %zu", this->name_, size, this->max_packet_size_);
+    return false;
+  }
+  size_t fragments = this->fragments_for_(size);
+  if (fragments > this->lower_->get_send_capacity()) {
+    ESP_LOGV(TAG, "%s: No room for %zu fragments", this->name_, fragments);
+    return false;
+  }
+  uint8_t header[HEADER_SIZE] = {this->tx_number_++, 0};
+  if (fragments == 1) {
+    header[1] = LAST_FRAGMENT;
+    return this->lower_->send_to_interface(PacketBuffer(header, HEADER_SIZE, &data, nullptr, 0), meta_data);
+  }
+  size_t fragment_size = this->fragment_size_();
+  for (size_t index = 0; index != fragments; index++) {
+    size_t length = data.copy_to(this->tx_buffer_, fragment_size, index * fragment_size);
+    header[1] = index | (index + 1 == fragments ? LAST_FRAGMENT : 0);
+    PacketBuffer body(this->tx_buffer_, length);
+    if (!this->lower_->send_to_interface(PacketBuffer(header, HEADER_SIZE, &body, nullptr, 0), meta_data)) {
+      // The peer drops the part already sent when the next packet starts
+      ESP_LOGV(TAG, "%s: Fragment %zu of %zu not accepted", this->name_, index, fragments);
+      return false;
+    }
+  }
+  return true;
+}
+
+void BasicFragmentation::receive_(const PacketBuffer &data, const PacketMetaData &meta_data) {
+  // Lower layers deliver packets in one piece; a packet in one fragment is passed up without copying
+  if (!data.is_contiguous()) {
+    ESP_LOGW(TAG, "%s: Packet split across buffers is not supported", this->name_);
+    return;
+  }
+  auto fragment = data.as_span();
+  if (fragment.size() < HEADER_SIZE) {
+    ESP_LOGV(TAG, "%s: Fragment of %zu bytes is shorter than its header, dropped", this->name_, fragment.size());
+    return;
+  }
+  uint8_t number = fragment[0];
+  uint8_t index = fragment[1] & INDEX_MASK;
+  bool last = (fragment[1] & LAST_FRAGMENT) != 0;
+  const uint8_t *payload = fragment.data() + HEADER_SIZE;
+  size_t length = fragment.size() - HEADER_SIZE;
+  if (index == 0 && last) {
+    // A packet in one fragment leaves a packet being joined from another device intact
+    if (this->rx_joining_ && meta_data.source_address == this->rx_source_) {
+      ESP_LOGV(TAG, "%s: Incomplete packet %u dropped", this->name_, this->rx_number_);
+      this->rx_joining_ = false;
+    }
+    if (length > this->max_packet_size_) {
+      ESP_LOGV(TAG, "%s: Packet %u is larger than %zu, dropped", this->name_, number, this->max_packet_size_);
+      return;
+    }
+    this->on_receive_from_interface_(PacketBuffer(payload, length), meta_data);
+    return;
+  }
+  if (index == 0) {
+    if (this->rx_joining_) {
+      ESP_LOGV(TAG, "%s: Incomplete packet %u dropped", this->name_, this->rx_number_);
+    }
+    this->rx_joining_ = true;
+    this->rx_number_ = number;
+    this->rx_source_ = meta_data.source_address;
+    this->rx_next_index_ = 0;
+    this->rx_length_ = 0;
+  } else if (this->rx_joining_ && meta_data.source_address != this->rx_source_) {
+    // Only this fragment is lost, so of two devices sending at once, the one that started last still gets through
+    ESP_LOGV(TAG, "%s: Fragment %u from 0x%04X dropped", this->name_, index, meta_data.source_address);
+    return;
+  } else if (!this->rx_joining_ || number != this->rx_number_ || index != this->rx_next_index_) {
+    ESP_LOGV(TAG, "%s: Fragment %u of packet %u dropped", this->name_, index, number);
+    this->rx_joining_ = false;
+    return;
+  }
+  if (this->rx_length_ + length > this->max_packet_size_) {
+    ESP_LOGV(TAG, "%s: Packet %u is larger than %zu, dropped", this->name_, number, this->max_packet_size_);
+    this->rx_joining_ = false;
+    return;
+  }
+  memcpy(this->rx_buffer_ + this->rx_length_, payload, length);
+  this->rx_length_ += length;
+  this->rx_next_index_++;
+  if (last) {
+    this->rx_joining_ = false;
+    this->on_receive_from_interface_(PacketBuffer(this->rx_buffer_, this->rx_length_), meta_data);
+  }
+}
+
+}  // namespace esphome::packet_interface
+#endif

esphome/components/packet_interface/basic_fragmentation.h

@@ -0,0 +1,60 @@
+#pragma once
+
+#include "esphome/core/defines.h"
+#ifdef USE_PACKET_INTERFACE_BASIC_FRAGMENTATION
+
+#include "packet_interface.h"
+
+namespace esphome::packet_interface {
+
+/**
+ * A fragmentation layer: packets up to this layer's max_packet_size are split into fragments that fit the layer
+ * below, and joined again at the other end.
+ *
+ * Each fragment starts with a 2 byte header: an 8-bit packet number, then the fragment's index in bits 0-6, with bit
+ * 7 set on the last fragment. A packet that fits in one fragment still has the header, and is sent and passed up
+ * without being copied.
+ *
+ * A packet is started only if the layer below can take all of its fragments now (get_send_capacity()), so a full
+ * reliability queue does not leave the peer with part of a packet. The receiver joins one packet at a time, and drops
+ * it when a fragment is missing or arrives with another packet number, or when the same source, or another one,
+ * starts a new packet of several fragments. Other fragments from another source address are dropped, leaving the
+ * packet being joined intact. Above a reliability layer, fragments arrive in order and none are missing.
+ */
+class BasicFragmentation : public PacketInterface {
+ public:
+  /// Packet number, then index and last flag.
+  static constexpr size_t HEADER_SIZE = 2;
+  /// The index has 7 bits.
+  static constexpr size_t MAX_FRAGMENTS = 128;
+
+  BasicFragmentation(PacketInterface *lower, size_t max_packet_size);
+
+  void setup() override;
+  void dump_config() override;
+  bool send_to_interface(const PacketBuffer &data, const PacketMetaData &meta_data) override;
+
+ protected:
+  void receive_(const PacketBuffer &data, const PacketMetaData &meta_data);
+  size_t fragment_size_() const {
+    size_t lower_size = this->lower_->get_max_packet_size();
+    return lower_size > HEADER_SIZE ? lower_size - HEADER_SIZE : 0;
+  }
+  size_t fragments_for_(size_t size) const;
+
+  PacketInterface *lower_;
+  // One fragment being sent, and the packet being joined; one block allocated in setup(), and tx_buffer_ stays null
+  // if that fails
+  uint8_t *tx_buffer_{nullptr};
+  uint8_t *rx_buffer_{nullptr};
+  size_t rx_length_{0};
+  uint16_t rx_source_{0};
+  uint8_t tx_number_{0};
+  uint8_t rx_number_{0};
+  uint8_t rx_next_index_{0};
+  bool rx_joining_{false};
+  bool queue_too_short_{false};
+};
+
+}  // namespace esphome::packet_interface
+#endif

esphome/components/packet_interface/basic_session.cpp

@@ -0,0 +1,135 @@
+#include "basic_session.h"
+#ifdef USE_PACKET_INTERFACE_BASIC_SESSION
+#include "esphome/core/application.h"
+#include "esphome/core/helpers.h"
+#include "esphome/core/log.h"
+
+namespace esphome::packet_interface {
+
+ESPHOME_LOG_TAG(TAG, "packet_interface.session");
+
+static constexpr uint8_t PACKET_TYPE_DATA = 0x00;
+static constexpr uint8_t PACKET_TYPE_KEEP_ALIVE = 0x01;
+// Type byte and the 32-bit boot id, little endian
+static constexpr size_t KEEP_ALIVE_SIZE = 5;
+
+BasicSession::BasicSession(PacketInterface *lower)
+    : PacketInterface(remaining_packet_size(lower->get_max_packet_size(), HEADER_SIZE)), lower_(lower) {
+  this->stack_on_(lower, CAPABILITY_SESSION);
+  // Data lost by a reliability layer below must be sent again, as after a restart of the peer
+  if (lower->has_capability(CAPABILITY_RELIABILITY)) {
+    lower->add_on_session_state_callback([this](bool connected) {
+      if (!connected && this->connected_)
+        this->set_connected_(false);
+    });
+  }
+}
+
+void BasicSession::setup() {
+  if (this->lower_->get_max_packet_size() < KEEP_ALIVE_SIZE) {
+    this->mark_failed(LOG_STR("max_packet_size too small for the configured layers"));
+    return;
+  }
+  this->boot_id_ = random_uint32();
+#ifdef USE_BINARY_SENSOR
+  if (this->connected_sensor_ != nullptr)
+    this->connected_sensor_->publish_initial_state(false);
+#endif
+  this->lower_->add_packet_interface_listener(
+      [this](const PacketBuffer &data, const PacketMetaData &meta_data) { this->receive_(data, meta_data); });
+  // A reliability layer below queues this until its link is up, so the peer hears of a restart straight away
+  this->send_keep_alive_();
+  this->set_interval(this->keep_alive_ms_, [this] { this->on_interval_(); });
+}
+
+void BasicSession::dump_config() {
+  ESP_LOGCONFIG(TAG,
+                "Basic Session on '%s':\n"
+                "  Max Packet Size: %zu\n"
+                "  Keep Alive: %" PRIu32 "ms\n"
+                "  Timeout: %" PRIu32 "ms",
+                this->name_, this->max_packet_size_, this->keep_alive_ms_, this->timeout_ms_);
+#ifdef USE_BINARY_SENSOR
+  LOG_BINARY_SENSOR("  ", "Connected", this->connected_sensor_);
+#endif
+}
+
+bool BasicSession::send_to_interface(const PacketBuffer &data, const PacketMetaData &meta_data) {
+  if (this->is_failed())
+    return false;
+  uint8_t header = PACKET_TYPE_DATA;
+  PacketBuffer packet(&header, HEADER_SIZE, &data, nullptr, 0);
+  return this->lower_->send_to_interface(packet, meta_data);
+}
+
+void BasicSession::send_keep_alive_() {
+  uint8_t packet[KEEP_ALIVE_SIZE] = {
+      PACKET_TYPE_KEEP_ALIVE, static_cast<uint8_t>(this->boot_id_), static_cast<uint8_t>(this->boot_id_ >> 8),
+      static_cast<uint8_t>(this->boot_id_ >> 16), static_cast<uint8_t>(this->boot_id_ >> 24)};
+  if (!this->lower_->send_to_interface(PacketBuffer(packet, sizeof(packet)), {}))
+    ESP_LOGV(TAG, "%s: Lower layer did not accept keep-alive", this->name_);
+}
+
+void BasicSession::on_interval_() {
+  this->send_keep_alive_();
+  if (this->connected_ && App.get_loop_component_start_time() - this->last_receive_ms_ > this->timeout_ms_) {
+    ESP_LOGW(TAG, "%s: Peer not heard for %" PRIu32 "ms", this->name_, this->timeout_ms_);
+    this->set_connected_(false);
+  }
+}
+
+void BasicSession::set_connected_(bool connected) {
+  this->connected_ = connected;
+  ESP_LOGD(TAG, "%s: Session %s", this->name_, connected ? LOG_STR_LITERAL("connected") : LOG_STR_LITERAL("lost"));
+#ifdef USE_BINARY_SENSOR
+  if (this->connected_sensor_ != nullptr)
+    this->connected_sensor_->publish_state(connected);
+#endif
+  this->session_callback_.call(connected);
+}
+
+void BasicSession::receive_(const PacketBuffer &data, const PacketMetaData &meta_data) {
+  // Lower layers deliver packets in one piece; the payload is passed up without copying
+  if (!data.is_contiguous()) {
+    ESP_LOGW(TAG, "%s: Packet split across buffers is not supported", this->name_);
+    return;
+  }
+  auto packet = data.as_span();
+  if (packet.empty()) {
+    this->note_received_(false);
+    return;
+  }
+  uint8_t type = packet[0];
+  if (type == PACKET_TYPE_KEEP_ALIVE) {
+    if (packet.size() != KEEP_ALIVE_SIZE) {
+      ESP_LOGV(TAG, "%s: Keep-alive of %zu bytes dropped", this->name_, packet.size());
+      this->note_received_(false);
+      return;
+    }
+    uint32_t boot_id = encode_uint32(packet[4], packet[3], packet[2], packet[1]);
+    if (!this->peer_known_ || boot_id != this->peer_boot_id_) {
+      // Data may arrive before the first keep-alive, so only a changed id means a restart
+      if (this->connected_ && this->peer_known_) {
+        ESP_LOGD(TAG, "%s: Peer has restarted", this->name_);
+        this->set_connected_(false);
+      }
+      this->peer_boot_id_ = boot_id;
+      this->peer_known_ = true;
+      // Answer a new peer at once; it answers only if our id is new to it, so this cannot repeat
+      this->send_keep_alive_();
+    }
+  } else if (type != PACKET_TYPE_DATA) {
+    ESP_LOGV(TAG, "%s: Unknown packet type 0x%02X dropped", this->name_, type);
+    this->note_received_(false);
+    return;
+  }
+  this->note_received_(true);
+  this->last_receive_ms_ = App.get_loop_component_start_time();
+  if (!this->connected_)
+    this->set_connected_(true);
+  if (type == PACKET_TYPE_DATA)
+    this->on_receive_from_interface_(PacketBuffer(packet.data() + HEADER_SIZE, packet.size() - HEADER_SIZE), meta_data);
+}
+
+}  // namespace esphome::packet_interface
+#endif

esphome/components/packet_interface/basic_session.h

@@ -0,0 +1,61 @@
+#pragma once
+
+#include "esphome/core/defines.h"
+#ifdef USE_PACKET_INTERFACE_BASIC_SESSION
+#include "packet_interface.h"
+#ifdef USE_BINARY_SENSOR
+#include "esphome/components/binary_sensor/binary_sensor.h"
+#endif
+
+namespace esphome::packet_interface {
+
+/**
+ * A session layer that reports whether the peer can be reached.
+ *
+ * Every packet starts with a type byte. A data packet carries the payload of the layer above. A keep-alive packet
+ * carries a random number chosen at boot, so that a restart of the peer is noticed even if it is quicker than the
+ * timeout. A keep-alive is sent every keep_alive interval, and at once when a new peer is heard. The peer is
+ * considered gone when nothing has been received from it for the timeout; this is checked every keep_alive interval.
+ * A restart of the peer is reported as a disconnect followed by a connect. So is a reset of a reliability layer below,
+ * which discards data: the session is reported lost, and connected again when the peer is next heard.
+ */
+class BasicSession : public PacketInterface {
+ public:
+  /// The packet type byte.
+  static constexpr size_t HEADER_SIZE = 1;
+
+  explicit BasicSession(PacketInterface *lower);
+
+  void setup() override;
+  void dump_config() override;
+  bool send_to_interface(const PacketBuffer &data, const PacketMetaData &meta_data) override;
+
+  void set_keep_alive(uint32_t keep_alive_ms) { this->keep_alive_ms_ = keep_alive_ms; }
+  void set_session_timeout(uint32_t timeout_ms) { this->timeout_ms_ = timeout_ms; }
+#ifdef USE_BINARY_SENSOR
+  void set_connected_sensor(binary_sensor::BinarySensor *sensor) { this->connected_sensor_ = sensor; }
+#endif
+
+  bool is_connected() const { return this->connected_; }
+
+ protected:
+  void receive_(const PacketBuffer &data, const PacketMetaData &meta_data);
+  void on_interval_();
+  void send_keep_alive_();
+  void set_connected_(bool connected);
+
+  PacketInterface *lower_;
+#ifdef USE_BINARY_SENSOR
+  binary_sensor::BinarySensor *connected_sensor_{nullptr};
+#endif
+  uint32_t keep_alive_ms_{10000};
+  uint32_t timeout_ms_{30000};
+  uint32_t last_receive_ms_{0};
+  uint32_t boot_id_{0};
+  uint32_t peer_boot_id_{0};
+  bool peer_known_{false};
+  bool connected_{false};
+};
+
+}  // namespace esphome::packet_interface
+#endif

esphome/components/packet_interface/hdlc_reliability.cpp

@@ -0,0 +1,365 @@
+#include "hdlc_reliability.h"
+#ifdef USE_PACKET_INTERFACE_HDLC
+#include "esphome/core/helpers.h"
+#include "esphome/core/log.h"
+
+namespace esphome::packet_interface {
+
+ESPHOME_LOG_TAG(TAG, "packet_interface.hdlc");
+
+static constexpr uint32_t RETRANSMIT_TIMER_ID = 0;
+static constexpr uint32_t ACK_TIMER_ID = 1;
+static constexpr uint32_t SEND_RETRY_TIMER_ID = 2;
+// A frame or acknowledgement the lower layer refused, for example while a radio was receiving, is sent again after this
+static constexpr uint32_t SEND_RETRY_MS = 50;
+// SABM is repeated at this interval, or the timeout if longer, until the peer answers
+static constexpr uint32_t RESET_INTERVAL_MS = 1000;
+
+// Control byte formats, with the poll/final bit (0x10) ignored
+static constexpr uint8_t POLL_FINAL_BIT = 0x10;
+static constexpr uint8_t SUPERVISORY_FRAME = 0x01;
+static constexpr uint8_t SUPERVISORY_RR = 0x00;
+static constexpr uint8_t SUPERVISORY_REJ = 0x02;
+static constexpr uint8_t UNNUMBERED_SABM = 0x2F;
+static constexpr uint8_t UNNUMBERED_UA = 0x63;
+
+static uint16_t frame_crc(uint8_t control, const uint8_t *payload, size_t length) {
+  uint16_t crc = crc16(&control, 1);
+  return crc16(payload, length, crc);
+}
+
+HdlcReliability::HdlcReliability(PacketInterface *lower)
+    : PacketInterface(remaining_packet_size(lower->get_max_packet_size(), FRAME_OVERHEAD)), lower_(lower) {
+  this->stack_on_(lower, CAPABILITY_RELIABILITY);
+}
+
+void HdlcReliability::setup() {
+  if (this->max_packet_size_ == 0) {
+    this->mark_failed(LOG_STR("max_packet_size too small for the configured layers"));
+    return;
+  }
+  RAMAllocator<uint8_t> allocator;
+  this->tx_slots_ = allocator.allocate(size_t{this->max_queue_length_} * this->max_packet_size_);
+  if (this->tx_slots_ == nullptr) {
+    this->mark_failed(LOG_STR("Not enough memory for the send queue"));
+    return;
+  }
+  this->lower_->add_packet_interface_listener(
+      [this](const PacketBuffer &data, const PacketMetaData &meta_data) { this->receive_(data, meta_data); });
+}
+
+void HdlcReliability::dump_config() {
+  ESP_LOGCONFIG(TAG,
+                "HDLC Reliability on '%s':\n"
+                "  Max Packet Size: %zu\n"
+                "  Timeout: %" PRIu32 "ms\n"
+                "  Ack Delay: %" PRIu32 "ms\n"
+                "  Max Queue Length: %u\n"
+                "  Max Retries: %u",
+                this->name_, this->max_packet_size_, this->timeout_ms_, this->ack_delay_ms_, this->max_queue_length_,
+                this->max_retries_);
+}
+
+void HdlcReliability::loop() {
+  // Disabled first, as sending may deliver a reply to this layer and request the loop again
+  this->disable_loop();
+  if (this->state_ == LinkState::LINK_STATE_RESET_PENDING) {
+    this->state_ = LinkState::LINK_STATE_RESETTING;
+    this->start_timer_();
+    this->send_frame_(UNNUMBERED_SABM, nullptr, 0);
+  }
+  if (this->state_ != LinkState::LINK_STATE_CONNECTED)
+    return;
+  // Queued frames go first, as each carries the acknowledgement
+  if (this->send_pending_() && this->ack_due_ && !this->send_supervisory_(SUPERVISORY_RR))
+    this->retry_send_();
+}
+
+void HdlcReliability::retry_send_() {
+  this->set_timeout(SEND_RETRY_TIMER_ID, SEND_RETRY_MS, [this]() { this->request_loop_(); });
+}
+
+void HdlcReliability::owe_ack_(bool now) {
+  if (now || this->ack_delay_ms_ == 0) {
+    this->ack_due_ = true;
+    this->request_loop_();
+  } else if (!this->ack_pending_) {
+    // Waiting lets one acknowledgement cover several frames, or a reply carry it
+    this->set_timeout(ACK_TIMER_ID, this->ack_delay_ms_, [this]() {
+      this->ack_due_ = true;
+      this->request_loop_();
+    });
+  }
+  this->ack_pending_ = true;
+}
+
+void HdlcReliability::ack_sent_() {
+  this->ack_pending_ = false;
+  this->ack_due_ = false;
+  this->cancel_timeout(ACK_TIMER_ID);
+}
+
+void HdlcReliability::request_loop_() { this->enable_loop(); }
+
+bool HdlcReliability::send_to_interface(const PacketBuffer &data, const PacketMetaData &meta_data) {
+  if (this->tx_slots_ == nullptr)
+    return false;
+  size_t size = data.size();
+  if (size > this->max_packet_size_) {
+    ESP_LOGW(TAG, "%s: Packet of %zu bytes is larger than %zu", this->name_, size, this->max_packet_size_);
+    return false;
+  }
+  uint8_t outstanding = this->outstanding_();
+  if (outstanding >= this->max_queue_length_) {
+    if (this->state_ == LinkState::LINK_STATE_CONNECTED) {
+      ESP_LOGV(TAG, "%s: Send queue full", this->name_);
+    } else if (!this->reset_wait_logged_) {
+      // Once for each reset; the layers above keep trying while the peer is away
+      this->reset_wait_logged_ = true;
+      ESP_LOGD(TAG, "%s: Send queue full, waiting for the peer to answer the link reset", this->name_);
+    }
+    return false;
+  }
+  uint8_t seq = this->vs_;
+  data.copy_to(this->slot_(seq), size);
+  this->tx_lengths_[this->slot_index_(seq)] = size;
+  this->vs_ = (seq + 1) & 7;
+  // While the link is being reset, the frame waits in the queue and is sent when UA arrives
+  if (this->state_ == LinkState::LINK_STATE_CONNECTED) {
+    this->send_pending_();
+    if (outstanding == 0)
+      this->start_timer_();
+  }
+  return true;
+}
+
+bool HdlcReliability::send_frame_(uint8_t control, const uint8_t *payload, size_t length) {
+  uint16_t crc = frame_crc(control, payload, length);
+  uint8_t trailer[2] = {static_cast<uint8_t>(crc), static_cast<uint8_t>(crc >> 8)};
+  PacketBuffer body(payload, length);
+  PacketBuffer frame(&control, 1, length != 0 ? &body : nullptr, trailer, sizeof(trailer));
+  if (this->lower_->send_to_interface(frame, {}))
+    return true;
+  ESP_LOGV(TAG, "%s: Lower layer did not accept frame 0x%02X", this->name_, control);
+  return false;
+}
+
+bool HdlcReliability::send_supervisory_(uint8_t type) {
+  if (!this->send_frame_(SUPERVISORY_FRAME | (type << 2) | (this->vr_ << 5), nullptr, 0))
+    return false;
+  this->ack_sent_();
+  return true;
+}
+
+// Sends the next queued frame not yet sent, and returns true if none are left. One frame per loop pass lets other
+// components run between frames: on a radio, sending blocks, and the peer's frames are received in between. If the
+// lower layer refuses the frame, it is sent again shortly.
+bool HdlcReliability::send_pending_() {
+  if (this->vn_ == this->vs_)
+    return true;
+  uint8_t control = (this->vn_ << 1) | (this->vr_ << 5);
+  if (!this->send_frame_(control, this->slot_(this->vn_), this->tx_lengths_[this->slot_index_(this->vn_)])) {
+    this->retry_send_();
+    return false;
+  }
+  // Every I-frame carries an acknowledgement, so a pending RR is no longer needed
+  this->ack_sent_();
+  this->vn_ = (this->vn_ + 1) & 7;
+  if (this->vn_ == this->vs_)
+    return true;
+  this->request_loop_();
+  return false;
+}
+
+void HdlcReliability::resend_outstanding_() {
+  this->vn_ = this->va_;
+  this->send_pending_();
+}
+
+void HdlcReliability::start_timer_() {
+  uint32_t interval = this->timeout_ms_;
+  if (this->state_ != LinkState::LINK_STATE_CONNECTED && interval < RESET_INTERVAL_MS)
+    interval = RESET_INTERVAL_MS;
+  // Up to a quarter longer at random, so devices whose frames collided on a shared channel do not resend together
+  interval += random_uint32() % (interval / 4 + 1);
+  this->set_timeout(RETRANSMIT_TIMER_ID, interval, [this]() { this->on_timeout_(); });
+}
+
+void HdlcReliability::on_timeout_() {
+  if (this->state_ != LinkState::LINK_STATE_CONNECTED) {
+    // Counted up to max_retries_ only, so the warning is logged once until the link comes up
+    if (this->retries_ < this->max_retries_) {
+      this->retries_++;
+      if (this->retries_ == this->max_retries_) {
+        ESP_LOGW(TAG, "%s: No answer to the link reset after %u tries; check that the peer has a reliability layer",
+                 this->name_, this->max_retries_);
+      }
+    }
+    this->send_frame_(UNNUMBERED_SABM, nullptr, 0);
+    this->start_timer_();
+    return;
+  }
+  if (this->outstanding_() == 0)
+    return;
+  if (this->retries_ == this->max_retries_) {
+    ESP_LOGW(TAG, "%s: No acknowledgement after %u retries, resetting link", this->name_, this->max_retries_);
+    this->start_reset_();
+    return;
+  }
+  this->retries_++;
+  ESP_LOGV(TAG, "%s: Timeout, resending %u frames", this->name_, this->outstanding_());
+  this->resend_outstanding_();
+  this->start_timer_();
+}
+
+// Unacknowledged frames are discarded; frames queued from now on are numbered from 0 and sent once the link is up.
+// Resetting a connected link can lose data both ways, which is reported to the layers above.
+void HdlcReliability::start_reset_() {
+  bool was_connected = this->state_ == LinkState::LINK_STATE_CONNECTED;
+  this->state_ = LinkState::LINK_STATE_RESET_PENDING;
+  this->va_ = this->vs_ = this->vn_ = 0;
+  this->head_ = 0;
+  this->vr_ = 0;
+  this->retries_ = 0;
+  this->rej_sent_ = false;
+  this->ack_sent_();
+  this->cancel_timeout(RETRANSMIT_TIMER_ID);
+  this->request_loop_();
+  if (was_connected)
+    this->session_callback_.call(false);
+}
+
+void HdlcReliability::link_up_() {
+  ESP_LOGD(TAG, "%s: Link connected", this->name_);
+  this->state_ = LinkState::LINK_STATE_CONNECTED;
+  this->reset_wait_logged_ = false;
+  this->peer_frame_seen_ = false;
+  this->retries_ = 0;
+  this->cancel_timeout(RETRANSMIT_TIMER_ID);
+  if (this->outstanding_() != 0) {
+    this->resend_outstanding_();
+    this->start_timer_();
+  }
+}
+
+void HdlcReliability::process_ack_(uint8_t nr) {
+  uint8_t acked = (nr - this->va_) & 7;
+  if (acked > this->outstanding_()) {
+    ESP_LOGV(TAG, "%s: Ignoring invalid N(R) %u", this->name_, nr);
+    return;
+  }
+  if (acked == 0)
+    return;
+  // The peer may have had frames that were refused when last resent
+  if (acked > ((this->vn_ - this->va_) & 7))
+    this->vn_ = nr;
+  this->head_ = (this->head_ + acked) % this->max_queue_length_;
+  this->va_ = nr;
+  this->retries_ = 0;
+  if (this->outstanding_() == 0) {
+    this->cancel_timeout(RETRANSMIT_TIMER_ID);
+  } else {
+    this->start_timer_();
+  }
+}
+
+void HdlcReliability::receive_(const PacketBuffer &data, const PacketMetaData &meta_data) {
+  // Lower layers deliver packets in one piece; the payload is passed up without copying
+  if (!data.is_contiguous()) {
+    ESP_LOGW(TAG, "%s: Packet split across buffers is not supported", this->name_);
+    return;
+  }
+  auto frame = data.as_span();
+  if (frame.size() < FRAME_OVERHEAD) {
+    this->note_received_(false);
+    return;
+  }
+  size_t length = frame.size() - FRAME_OVERHEAD;
+  uint8_t control = frame[0];
+  const uint8_t *payload = frame.data() + 1;
+  uint16_t crc = frame[length + 1] | (frame[length + 2] << 8);
+  if (frame_crc(control, payload, length) != crc) {
+    ESP_LOGV(TAG, "%s: CRC error, frame dropped", this->name_);
+    this->note_received_(false);
+    return;
+  }
+  // The peer's packets may only be larger if it has a larger max_packet_size, which the layers above cannot take
+  if (length > this->max_packet_size_) {
+    if (!this->oversize_warned_) {
+      this->oversize_warned_ = true;
+      ESP_LOGW(TAG,
+               "%s: Frame of %zu bytes is larger than %zu, dropped; check that both devices use the same "
+               "max_packet_size",
+               this->name_, length, this->max_packet_size_);
+    } else {
+      ESP_LOGV(TAG, "%s: Frame of %zu bytes is larger than %zu, dropped", this->name_, length, this->max_packet_size_);
+    }
+    this->note_received_(false);
+    return;
+  }
+  this->note_received_(true);
+
+  uint8_t command = control & ~POLL_FINAL_BIT;
+  if (command == UNNUMBERED_SABM) {
+    // A peer that has not heard our UA repeats its SABM, and cannot have sent a numbered frame meanwhile; answering
+    // again keeps this side connected, and the queued frames, instead of treating the repeat as a restart.
+    if (this->state_ == LinkState::LINK_STATE_CONNECTED && this->peer_frame_seen_) {
+      // The peer has restarted, so frames it has not acknowledged are lost
+      ESP_LOGD(TAG, "%s: Link reset by peer", this->name_);
+      this->start_reset_();
+    }
+    this->vr_ = 0;
+    this->rej_sent_ = false;
+    this->send_frame_(UNNUMBERED_UA, nullptr, 0);
+    // Both sides now start from 0, so the link is up even if our own SABM is unanswered
+    this->link_up_();
+    return;
+  }
+  if (command == UNNUMBERED_UA) {
+    if (this->state_ == LinkState::LINK_STATE_RESETTING)
+      this->link_up_();
+    return;
+  }
+  // Numbered frames are ignored until the link is reset; the peer answers our SABM first
+  if (this->state_ != LinkState::LINK_STATE_CONNECTED)
+    return;
+  this->peer_frame_seen_ = true;
+
+  uint8_t nr = control >> 5;
+  if ((control & 1) == 0) {
+    this->process_ack_(nr);
+    this->receive_info_(control, payload, length, meta_data);
+    return;
+  }
+  if ((control & 3) != SUPERVISORY_FRAME)
+    return;
+  this->process_ack_(nr);
+  if (((control >> 2) & 3) == SUPERVISORY_REJ && this->outstanding_() != 0) {
+    ESP_LOGV(TAG, "%s: Peer rejected from %u", this->name_, nr);
+    this->resend_outstanding_();
+    this->start_timer_();
+  }
+}
+
+void HdlcReliability::receive_info_(uint8_t control, const uint8_t *payload, size_t length,
+                                    const PacketMetaData &meta_data) {
+  uint8_t ns = (control >> 1) & 7;
+  if (ns != this->vr_) {
+    // A gap or a duplicate; ask once for a resend from the expected frame, then just acknowledge at once
+    if (!this->rej_sent_) {
+      this->rej_sent_ = this->send_supervisory_(SUPERVISORY_REJ);
+      if (this->rej_sent_)
+        return;
+    }
+    this->owe_ack_(true);
+    return;
+  }
+  this->vr_ = (this->vr_ + 1) & 7;
+  this->rej_sent_ = false;
+  // The acknowledgement is sent from loop(), so a reply sent from the callback can carry it instead
+  this->owe_ack_(false);
+  this->on_receive_from_interface_(PacketBuffer(payload, length), meta_data);
+}
+
+}  // namespace esphome::packet_interface
+#endif

esphome/components/packet_interface/hdlc_reliability.h

@@ -0,0 +1,99 @@
+#pragma once
+
+#include "esphome/core/defines.h"
+#ifdef USE_PACKET_INTERFACE_HDLC
+#include <array>
+
+#include "packet_interface.h"
+
+namespace esphome::packet_interface {
+
+/**
+ * A reliability layer that delivers packets in order, without loss or duplicates, between two peers.
+ *
+ * It follows HDLC asynchronous balanced mode, with sequence numbers modulo 8 and go-back-N retransmission:
+ * - I-frames carry a payload, the sequence number N(S) and an acknowledgement N(R) of the peer's frames.
+ * - RR frames acknowledge without a payload; REJ frames ask the peer to resend from N(R).
+ * - SABM resets both peers' sequence numbers, and UA answers it.
+ *
+ * Each frame is the HDLC control byte, the payload, then a CRC-16 of both in little endian order.
+ * Unacknowledged frames are resent after the timeout; after max_retries the link is reset.
+ */
+class HdlcReliability : public PacketInterface {
+ public:
+  /// Most frames that can be unacknowledged at once, set by the 3 bit sequence numbers.
+  static constexpr uint8_t MAX_WINDOW = 7;
+  /// Control byte plus CRC-16.
+  static constexpr size_t FRAME_OVERHEAD = 3;
+
+  explicit HdlcReliability(PacketInterface *lower);
+
+  void setup() override;
+  void loop() override;
+  void dump_config() override;
+  bool send_to_interface(const PacketBuffer &data, const PacketMetaData &meta_data) override;
+  /// No room while the layer has no send queue: before setup(), or when setup() failed.
+  size_t get_send_capacity() const override {
+    return this->tx_slots_ == nullptr ? 0 : this->max_queue_length_ - this->outstanding_();
+  }
+
+  void set_ack_timeout(uint32_t timeout_ms) { this->timeout_ms_ = timeout_ms; }
+  void set_ack_delay(uint32_t ack_delay_ms) { this->ack_delay_ms_ = ack_delay_ms; }
+  void set_max_queue_length(uint8_t length) { this->max_queue_length_ = length; }
+  void set_max_retries(uint8_t retries) { this->max_retries_ = retries; }
+
+  bool is_connected() const { return this->state_ == LinkState::LINK_STATE_CONNECTED; }
+
+ protected:
+  enum class LinkState : uint8_t {
+    LINK_STATE_RESET_PENDING,  // SABM to be sent from loop()
+    LINK_STATE_RESETTING,      // SABM sent, waiting for UA
+    LINK_STATE_CONNECTED,
+  };
+
+  void receive_(const PacketBuffer &data, const PacketMetaData &meta_data);
+  void receive_info_(uint8_t control, const uint8_t *payload, size_t length, const PacketMetaData &meta_data);
+  bool send_frame_(uint8_t control, const uint8_t *payload, size_t length);
+  bool send_supervisory_(uint8_t type);
+  bool send_pending_();
+  void resend_outstanding_();
+  void retry_send_();
+  /// An RR is owed: at once, or after the ack delay unless an I-frame carries it first.
+  void owe_ack_(bool now);
+  void ack_sent_();
+  void process_ack_(uint8_t nr);
+  void on_timeout_();
+  void start_reset_();
+  void link_up_();
+  void start_timer_();
+  void request_loop_();
+  uint8_t outstanding_() const { return (this->vs_ - this->va_) & 7; }
+  uint8_t slot_index_(uint8_t seq) const { return (this->head_ + ((seq - this->va_) & 7)) % this->max_queue_length_; }
+  uint8_t *slot_(uint8_t seq) { return this->tx_slots_ + this->slot_index_(seq) * this->max_packet_size_; }
+
+  PacketInterface *lower_;
+  // max_queue_length_ slots of max_packet_size_ bytes, a ring starting at head_ which holds frame va_; allocated in
+  // setup() and never freed
+  uint8_t *tx_slots_{nullptr};
+  std::array<uint16_t, MAX_WINDOW> tx_lengths_{};  // indexed like the slots
+  uint32_t timeout_ms_{200};
+  uint32_t ack_delay_ms_{0};
+  uint8_t max_queue_length_{4};
+  uint8_t max_retries_{5};
+  uint8_t retries_{0};
+  uint8_t head_{0};
+  uint8_t vs_{0};  // sequence number of the next new frame
+  uint8_t vn_{0};  // next frame to send; frames from va_ up to it have been sent
+  uint8_t va_{0};  // oldest unacknowledged frame
+  uint8_t vr_{0};  // next frame expected from the peer
+  LinkState state_{LinkState::LINK_STATE_RESET_PENDING};
+  bool ack_pending_{false};  // an RR is owed
+  bool ack_due_{false};      // and should be sent now
+  bool rej_sent_{false};
+  bool peer_frame_seen_{false};  // a numbered frame has arrived since the link came up
+  bool oversize_warned_{false};
+  bool reset_wait_logged_{false};  // the queue filled while waiting for this reset to be answered
+};
+
+}  // namespace esphome::packet_interface
+#endif

esphome/components/packet_interface/layers/__init__.py

@@ -0,0 +1,238 @@
+"""The kinds of layer that can be stacked on a packet interface, and the registry of their implementations.
+
+Each module in this package implements one layer type and registers it with its kind, for example:
+
+    @RELIABILITY.register("hdlc", schema=HDLC_SCHEMA, single_peer=lambda config: True)
+    async def build_hdlc(config: ConfigType, lower: MockObj) -> MockObj:
+        ...
+
+The packet_interface component imports every module here before it builds its schemas, so a new layer type needs
+only a new module. The kinds, and the order in which they are stacked, are fixed here.
+"""
+
+from collections.abc import Awaitable, Callable
+from dataclasses import dataclass
+from typing import Any
+
+import esphome.codegen as cg
+import esphome.config_validation as cv
+from esphome.const import CONF_ENCRYPTION, CONF_FRAGMENTATION, CONF_KEY, CONF_TYPE
+from esphome.cpp_generator import MockObj
+from esphome.types import ConfigType
+
+packet_interface_ns = cg.esphome_ns.namespace("packet_interface")
+PacketInterface = packet_interface_ns.class_("PacketInterface", cg.Component)
+
+CONF_ADDRESSING = "addressing"
+CONF_DESTINATION = "destination"
+CONF_PEERS = "peers"
+CONF_RELIABILITY = "reliability"
+CONF_SESSION = "session"
+
+BROADCAST_ADDRESS = 0xFFFF
+
+# Builds a layer above lower and returns it. An addressing layer instead returns a list of (port, config) pairs, one
+# for each stack it carries, where config holds the layers for that stack, or is None for the layers on the link.
+LayerBuilder = Callable[[ConfigType, MockObj], Awaitable[Any]]
+
+
+def _never(config: ConfigType) -> bool:
+    return False
+
+
+def _nothing(config: ConfigType) -> list[str]:
+    return []
+
+
+def _same_size(config: ConfigType, size: int) -> int:
+    return size
+
+
+def _no_limit(config: ConfigType) -> int | None:
+    return None
+
+
+def _fits(config: ConfigType, size: int, capacity: int | None) -> None:
+    """Accept any layer below."""
+
+
+@dataclass(frozen=True)
+class LayerType:
+    """One implementation of a kind of layer."""
+
+    # Returns the schema; called once every layer type is registered, as some schemas contain other layers
+    schema_factory: Callable[[], Any]
+    build: LayerBuilder
+    # True if this configuration keeps state for one peer, so cannot be used with broadcast addressing
+    single_peer: Callable[[ConfigType], bool]
+    # True if this configuration works only when the peer sends packets back, which a session layer makes sure of
+    needs_session: Callable[[ConfigType], bool]
+    # The components this configuration needs loaded
+    auto_load: Callable[[ConfigType], list[str]]
+    # The largest packet this configuration takes, from the largest that the layer below takes, as the C++ works it out
+    packet_size: Callable[[ConfigType, int], int]
+    # How many packets this configuration takes at once, or None for no limit
+    send_capacity: Callable[[ConfigType], int | None]
+    # Raises cv.Invalid if this configuration cannot work above a layer with this packet size and send capacity
+    check_lower: Callable[[ConfigType, int, int | None], None]
+
+
+class LayerKind:
+    """A kind of layer, such as encryption, with the types that implement it."""
+
+    def __init__(
+        self, key: str, default_type: str, shorthand: str | None = None
+    ) -> None:
+        self.key = key
+        self.default_type = default_type
+        # The option that a plain string value sets, as in `encryption: my key`
+        self.shorthand = shorthand
+        self.types: dict[str, LayerType] = {}
+        # Set once the schema is built, as types registered after that would not be in it
+        self.frozen = False
+
+    def register(
+        self,
+        name: str,
+        *,
+        schema: Any = None,
+        schema_factory: Callable[[], Any] | None = None,
+        single_peer: Callable[[ConfigType], bool] = _never,
+        needs_session: Callable[[ConfigType], bool] = _never,
+        auto_load: Callable[[ConfigType], list[str]] = _nothing,
+        packet_size: Callable[[ConfigType, int], int] = _same_size,
+        send_capacity: Callable[[ConfigType], int | None] = _no_limit,
+        check_lower: Callable[[ConfigType, int, int | None], None] = _fits,
+    ) -> Callable[[LayerBuilder], LayerBuilder]:
+        """Register a type with its schema, or with a function returning a schema that contains other layers."""
+
+        def fixed_schema() -> Any:
+            return schema
+
+        def decorator(build: LayerBuilder) -> LayerBuilder:
+            if self.frozen:
+                raise ValueError(
+                    f"{self.key} layer type '{name}' is registered after the schemas were built; register it "
+                    "before the packet_interface component is imported"
+                )
+            if name in self.types:
+                raise ValueError(
+                    f"{self.key} layer type '{name}' is already registered"
+                )
+            self.types[name] = LayerType(
+                schema_factory or fixed_schema,
+                build,
+                single_peer,
+                needs_session,
+                auto_load,
+                packet_size,
+                send_capacity,
+                check_lower,
+            )
+            return build
+
+        return decorator
+
+    def _expand(self, value: Any) -> Any:
+        """Allow a layer to be enabled with no options, as in `reliability:`, or with its shorthand."""
+        if value is None:
+            return {}
+        if self.shorthand is not None and isinstance(value, str):
+            return {self.shorthand: value}
+        return value
+
+    def schema(self) -> Callable[[Any], ConfigType]:
+        """The schema for this kind; no type can be registered after this."""
+        self.frozen = True
+        return cv.All(
+            self._expand,
+            cv.typed_schema(
+                {name: layer.schema_factory() for name, layer in self.types.items()},
+                default_type=self.default_type,
+            ),
+        )
+
+    def get_type(self, config: ConfigType) -> LayerType:
+        return self.types[config[CONF_TYPE]]
+
+
+# An addressing type's configuration has either a destination or a list of peers, each with an id, a destination
+# and its own layers.
+ADDRESSING = LayerKind(CONF_ADDRESSING, "basic")
+ENCRYPTION = LayerKind(CONF_ENCRYPTION, "xxtea", shorthand=CONF_KEY)
+RELIABILITY = LayerKind(CONF_RELIABILITY, "hdlc")
+FRAGMENTATION = LayerKind(CONF_FRAGMENTATION, "basic")
+SESSION = LayerKind(CONF_SESSION, "basic")
+# The kinds stacked above the link, or above each port of an addressing layer, from the bottom up
+STACK_ORDER = (ENCRYPTION, RELIABILITY, FRAGMENTATION, SESSION)
+
+
+def stack_schema() -> dict:
+    """Schema entries for the layers of one stack; call only once all layer types are registered."""
+    return {cv.Optional(kind.key): kind.schema() for kind in STACK_ORDER}
+
+
+def check_session(config: ConfigType) -> None:
+    """Layers that need packets back from the peer need a session layer, whose keep-alives send them."""
+    if CONF_SESSION in config:
+        return
+    for kind in STACK_ORDER:
+        if (layer := config.get(kind.key)) is not None and kind.get_type(
+            layer
+        ).needs_session(layer):
+            raise cv.Invalid(
+                f"This '{kind.key}' needs packets from the peer, so it needs a '{CONF_SESSION}' layer, whose "
+                "keep-alives make sure they are sent",
+                path=[kind.key],
+            )
+
+
+def check_single_peer(config: ConfigType, destination: int) -> None:
+    """Layers that keep state for one peer need a destination other than broadcast."""
+    if destination != BROADCAST_ADDRESS:
+        return
+    for kind in STACK_ORDER:
+        if (layer := config.get(kind.key)) is not None and kind.get_type(
+            layer
+        ).single_peer(layer):
+            raise cv.Invalid(
+                f"This '{kind.key}' works between two devices only, so it needs a '{CONF_DESTINATION}' other than "
+                "broadcast",
+                path=[kind.key],
+            )
+
+
+def remaining_packet_size(size: int, used: int) -> int:
+    return max(size - used, 0)
+
+
+def check_packet_sizes(config: ConfigType, size: int) -> None:
+    """Check each layer in config against the layer below it; size is the largest packet that the stack sits on takes."""
+    capacity = None
+    for kind in STACK_ORDER:
+        if (layer := config.get(kind.key)) is None:
+            continue
+        layer_type = kind.get_type(layer)
+        try:
+            layer_type.check_lower(layer, size, capacity)
+        except cv.Invalid as err:
+            err.prepend([kind.key])
+            raise
+        size = layer_type.packet_size(layer, size)
+        capacity = layer_type.send_capacity(layer)
+
+
+def stack_auto_load(config: ConfigType) -> set[str]:
+    """The components that the layers configured in config need loaded."""
+    loads: set[str] = set()
+    for kind in STACK_ORDER:
+        if (layer := config.get(kind.key)) is not None:
+            loads.update(kind.get_type(layer).auto_load(layer))
+    return loads
+
+
+async def build_stack(config: ConfigType, lower: MockObj) -> None:
+    """Create the layers configured in config, from the bottom up, above lower."""
+    for kind in STACK_ORDER:
+        if (layer := config.get(kind.key)) is not None:
+            lower = await kind.get_type(layer).build(layer, lower)

esphome/components/packet_interface/layers/basic_addressing.py

@@ -0,0 +1,132 @@
+"""Addressing layer with 16-bit addresses, carrying one stack of layers or one for each of several peers."""
+
+from typing import Any
+
+import esphome.codegen as cg
+import esphome.config_validation as cv
+from esphome.const import CONF_ADDRESS, CONF_ID
+from esphome.core import ID
+from esphome.cpp_generator import MockObj
+from esphome.types import ConfigType
+
+from . import (
+    ADDRESSING,
+    BROADCAST_ADDRESS,
+    CONF_DESTINATION,
+    CONF_PEERS,
+    PacketInterface,
+    check_session,
+    check_single_peer,
+    packet_interface_ns,
+    remaining_packet_size,
+    stack_schema,
+)
+
+CONF_PORT_ID = "port_id"
+
+# The destination and source addresses
+HEADER_SIZE = 4
+
+BasicAddressing = packet_interface_ns.class_("BasicAddressing", cg.Component)
+AddressingPort = packet_interface_ns.class_("AddressingPort", PacketInterface)
+
+_request_port_slot = cg.slot_counter("PACKET_INTERFACE_ADDRESSING_PORT_COUNT")
+
+
+def _destination(value: Any) -> int:
+    """A device address, or broadcast."""
+    if isinstance(value, str) and value.lower() == "broadcast":
+        return BROADCAST_ADDRESS
+    return cv.hex_int_range(1, BROADCAST_ADDRESS)(value)
+
+
+def _validate_peer(config: ConfigType) -> ConfigType:
+    check_session(config)
+    check_single_peer(config, config[CONF_DESTINATION])
+    return config
+
+
+def _unique_destinations(peers: list[ConfigType]) -> list[ConfigType]:
+    destinations = [peer[CONF_DESTINATION] for peer in peers]
+    if len(set(destinations)) != len(destinations):
+        raise cv.Invalid("Each peer must have a different destination")
+    return peers
+
+
+def _not_own_address(config: ConfigType) -> ConfigType:
+    """Packets from this device's own address are dropped as echoes, so it cannot be a destination."""
+    address = config[CONF_ADDRESS]
+    if config.get(CONF_DESTINATION) == address:
+        raise cv.Invalid(
+            "Must not be this device's own address", path=[CONF_DESTINATION]
+        )
+    for index, peer in enumerate(config.get(CONF_PEERS, [])):
+        if peer[CONF_DESTINATION] == address:
+            raise cv.Invalid(
+                "Must not be this device's own address",
+                path=[CONF_PEERS, index, CONF_DESTINATION],
+            )
+    return config
+
+
+# A function, as each peer holds the other layers, whose schemas exist only once every layer type is registered
+def _basic_addressing_schema() -> cv.Schema:
+    peer_schema = cv.All(
+        cv.Schema(
+            {
+                cv.Required(CONF_ID): cv.declare_id(AddressingPort),
+                cv.Required(CONF_DESTINATION): _destination,
+                **stack_schema(),
+            }
+        ),
+        _validate_peer,
+    )
+    return cv.All(
+        cv.Schema(
+            {
+                cv.GenerateID(): cv.declare_id(BasicAddressing),
+                cv.GenerateID(CONF_PORT_ID): cv.declare_id(AddressingPort),
+                cv.Required(CONF_ADDRESS): cv.hex_int_range(1, BROADCAST_ADDRESS - 1),
+                cv.Optional(CONF_DESTINATION): _destination,
+                cv.Optional(CONF_PEERS): cv.All(
+                    cv.ensure_list(peer_schema), cv.Length(min=1), _unique_destinations
+                ),
+            }
+        ).extend(cv.COMPONENT_SCHEMA),
+        cv.has_at_most_one_key(CONF_DESTINATION, CONF_PEERS),
+        _not_own_address,
+    )
+
+
+async def _new_port(
+    port_id: ID, addressing: MockObj, destination: int, only_port: bool
+) -> MockObj:
+    _request_port_slot(str(addressing))
+    port = cg.new_Pvariable(port_id, addressing, destination, only_port)
+    await cg.register_component(port, {})
+    return port
+
+
+@ADDRESSING.register(
+    "basic",
+    schema_factory=_basic_addressing_schema,
+    packet_size=lambda config, size: remaining_packet_size(size, HEADER_SIZE),
+)
+async def build_basic_addressing(
+    config: ConfigType, link: MockObj
+) -> list[tuple[MockObj, ConfigType | None]]:
+    cg.add_define("USE_PACKET_INTERFACE_BASIC_ADDRESSING")
+    hub = cg.new_Pvariable(config[CONF_ID], link, config[CONF_ADDRESS])
+    await cg.register_component(hub, config)
+    if (peers := config.get(CONF_PEERS)) is None:
+        port = await _new_port(
+            config[CONF_PORT_ID], hub, config[CONF_DESTINATION], True
+        )
+        return [(port, None)]
+    stacks = []
+    # Each peer has its own stack, named after the peer for logs and saved preferences
+    for peer in peers:
+        port = await _new_port(peer[CONF_ID], hub, peer[CONF_DESTINATION], False)
+        cg.add(port.set_name(peer[CONF_ID].id))
+        stacks.append((port, peer))
+    return stacks

esphome/components/packet_interface/layers/basic_fragmentation.py

@@ -0,0 +1,56 @@
+"""Fragmentation layer that splits packets larger than the layers below allow, and joins them again."""
+
+import math
+
+import esphome.codegen as cg
+from esphome.components.const import CONF_MAX_PACKET_SIZE
+import esphome.config_validation as cv
+from esphome.const import CONF_ID
+from esphome.cpp_generator import MockObj
+from esphome.types import ConfigType
+
+from . import FRAGMENTATION, PacketInterface, packet_interface_ns
+
+# The packet number, and the fragment's index with the flag on the last fragment
+HEADER_SIZE = 2
+MAX_FRAGMENTS = 128
+
+BasicFragmentation = packet_interface_ns.class_("BasicFragmentation", PacketInterface)
+
+BASIC_FRAGMENTATION_SCHEMA = cv.Schema(
+    {
+        cv.GenerateID(): cv.declare_id(BasicFragmentation),
+        # The packet being joined is held in a buffer of this size
+        cv.Optional(CONF_MAX_PACKET_SIZE, default=1024): cv.int_range(16, 16384),
+    }
+).extend(cv.COMPONENT_SCHEMA)
+
+
+def _check_lower(config: ConfigType, size: int, capacity: int | None) -> None:
+    """The largest packet must fit in the fragments that the layer below can take at once."""
+    fragment_size = size - HEADER_SIZE
+    if fragment_size <= 0:
+        raise cv.Invalid("The layers below leave no room for fragments")
+    fragments = max(1, math.ceil(config[CONF_MAX_PACKET_SIZE] / fragment_size))
+    limit = MAX_FRAGMENTS if capacity is None else min(MAX_FRAGMENTS, capacity)
+    if fragments > limit:
+        raise cv.Invalid(
+            f"A packet of {config[CONF_MAX_PACKET_SIZE]} bytes needs {fragments} fragments of {fragment_size} bytes, "
+            f"but at most {limit} can be sent at once",
+            path=[CONF_MAX_PACKET_SIZE],
+        )
+
+
+# Fragments from different devices are told apart by the addressing layer's source address, so of two devices sending
+# fragmented packets at once, one still gets through; without addressing, the receiver can drop both
+@FRAGMENTATION.register(
+    "basic",
+    schema=BASIC_FRAGMENTATION_SCHEMA,
+    packet_size=lambda config, size: config[CONF_MAX_PACKET_SIZE],
+    check_lower=_check_lower,
+)
+async def build_basic_fragmentation(config: ConfigType, lower: MockObj) -> MockObj:
+    cg.add_define("USE_PACKET_INTERFACE_BASIC_FRAGMENTATION")
+    var = cg.new_Pvariable(config[CONF_ID], lower, config[CONF_MAX_PACKET_SIZE])
+    await cg.register_component(var, config)
+    return var

esphome/components/packet_interface/layers/basic_session.py

@@ -0,0 +1,71 @@
+"""Session layer that sends keep-alives and reports whether the peer can be reached."""
+
+import esphome.codegen as cg
+from esphome.components import binary_sensor
+import esphome.config_validation as cv
+from esphome.const import (
+    CONF_BINARY_SENSOR,
+    CONF_ID,
+    CONF_TIMEOUT,
+    DEVICE_CLASS_CONNECTIVITY,
+    ENTITY_CATEGORY_DIAGNOSTIC,
+)
+from esphome.cpp_generator import MockObj
+from esphome.types import ConfigType
+
+from . import SESSION, PacketInterface, packet_interface_ns
+
+CONF_KEEP_ALIVE = "keep_alive"
+
+BasicSession = packet_interface_ns.class_("BasicSession", PacketInterface)
+
+
+def _session_timeout(config: ConfigType) -> ConfigType:
+    """Default the timeout to three keep-alive intervals, and require it to be longer than one."""
+    keep_alive = config[CONF_KEEP_ALIVE].total_milliseconds
+    if (timeout := config.get(CONF_TIMEOUT)) is None:
+        config[CONF_TIMEOUT] = cv.positive_time_period_milliseconds(
+            f"{keep_alive * 3}ms"
+        )
+    elif timeout.total_milliseconds <= keep_alive:
+        raise cv.Invalid("Must be longer than keep_alive", path=[CONF_TIMEOUT])
+    return config
+
+
+BASIC_SESSION_SCHEMA = cv.All(
+    cv.Schema(
+        {
+            cv.GenerateID(): cv.declare_id(BasicSession),
+            cv.Optional(CONF_KEEP_ALIVE, default="10s"): cv.All(
+                cv.positive_time_period_milliseconds,
+                cv.Range(min=cv.TimePeriod(seconds=1), max=cv.TimePeriod(hours=1)),
+            ),
+            cv.Optional(CONF_TIMEOUT): cv.All(
+                cv.positive_time_period_milliseconds,
+                cv.Range(max=cv.TimePeriod(hours=3)),
+            ),
+            cv.Optional(CONF_BINARY_SENSOR): binary_sensor.binary_sensor_schema(
+                device_class=DEVICE_CLASS_CONNECTIVITY,
+                entity_category=ENTITY_CATEGORY_DIAGNOSTIC,
+            ),
+        }
+    ).extend(cv.COMPONENT_SCHEMA),
+    _session_timeout,
+)
+
+
+@SESSION.register(
+    "basic",
+    schema=BASIC_SESSION_SCHEMA,
+    single_peer=lambda config: True,
+    auto_load=lambda config: ["binary_sensor"] if CONF_BINARY_SENSOR in config else [],
+)
+async def build_basic_session(config: ConfigType, lower: MockObj) -> MockObj:
+    cg.add_define("USE_PACKET_INTERFACE_BASIC_SESSION")
+    var = cg.new_Pvariable(config[CONF_ID], lower)
+    cg.add(var.set_keep_alive(config[CONF_KEEP_ALIVE]))
+    cg.add(var.set_session_timeout(config[CONF_TIMEOUT]))
+    await cg.register_component(var, config)
+    binary_sensors = binary_sensor.sub_binary_sensors(config)
+    await binary_sensors(CONF_BINARY_SENSOR, var.set_connected_sensor)
+    return var

esphome/components/packet_interface/layers/hdlc_reliability.py

@@ -0,0 +1,68 @@
+"""Reliability layer using HDLC style acknowledgement and go-back-N retransmission."""
+
+import esphome.codegen as cg
+import esphome.config_validation as cv
+from esphome.const import CONF_ID, CONF_TIMEOUT
+from esphome.cpp_generator import MockObj
+from esphome.types import ConfigType
+
+from . import RELIABILITY, PacketInterface, packet_interface_ns, remaining_packet_size
+
+CONF_ACK_DELAY = "ack_delay"
+CONF_MAX_QUEUE_LENGTH = "max_queue_length"
+CONF_MAX_RETRIES = "max_retries"
+
+# The control byte and the CRC-16
+FRAME_OVERHEAD = 3
+
+HdlcReliability = packet_interface_ns.class_("HdlcReliability", PacketInterface)
+
+
+def _ack_delay_within_timeout(config: ConfigType) -> ConfigType:
+    """The peer, configured the same, must hear the acknowledgement before its timeout."""
+    if (
+        config[CONF_ACK_DELAY].total_milliseconds
+        >= config[CONF_TIMEOUT].total_milliseconds
+    ):
+        raise cv.Invalid(
+            f"Must be shorter than '{CONF_TIMEOUT}'", path=[CONF_ACK_DELAY]
+        )
+    return config
+
+
+HDLC_SCHEMA = cv.All(
+    cv.Schema(
+        {
+            cv.GenerateID(): cv.declare_id(HdlcReliability),
+            # Retransmitting more often than the main loop runs would exhaust the retries at once
+            cv.Optional(CONF_TIMEOUT, default="200ms"): cv.All(
+                cv.positive_time_period_milliseconds,
+                cv.Range(min=cv.TimePeriod(milliseconds=50)),
+            ),
+            cv.Optional(
+                CONF_ACK_DELAY, default="0ms"
+            ): cv.positive_time_period_milliseconds,
+            cv.Optional(CONF_MAX_QUEUE_LENGTH, default=4): cv.int_range(1, 7),
+            cv.Optional(CONF_MAX_RETRIES, default=5): cv.int_range(1, 255),
+        }
+    ).extend(cv.COMPONENT_SCHEMA),
+    _ack_delay_within_timeout,
+)
+
+
+@RELIABILITY.register(
+    "hdlc",
+    schema=HDLC_SCHEMA,
+    single_peer=lambda config: True,
+    packet_size=lambda config, size: remaining_packet_size(size, FRAME_OVERHEAD),
+    send_capacity=lambda config: config[CONF_MAX_QUEUE_LENGTH],
+)
+async def build_hdlc(config: ConfigType, lower: MockObj) -> MockObj:
+    cg.add_define("USE_PACKET_INTERFACE_HDLC")
+    var = cg.new_Pvariable(config[CONF_ID], lower)
+    cg.add(var.set_ack_timeout(config[CONF_TIMEOUT]))
+    cg.add(var.set_ack_delay(config[CONF_ACK_DELAY]))
+    cg.add(var.set_max_queue_length(config[CONF_MAX_QUEUE_LENGTH]))
+    cg.add(var.set_max_retries(config[CONF_MAX_RETRIES]))
+    await cg.register_component(var, config)
+    return var

esphome/components/packet_interface/layers/xxtea_encryption.py

@@ -0,0 +1,61 @@
+"""Encryption layer using XXTEA, with an optional rolling code."""
+
+import hashlib
+
+import esphome.codegen as cg
+import esphome.config_validation as cv
+from esphome.const import CONF_ID, CONF_KEY
+from esphome.cpp_generator import MockObj
+from esphome.types import ConfigType
+
+from . import ENCRYPTION, PacketInterface, packet_interface_ns, remaining_packet_size
+
+CONF_ROLLING_CODE_ENABLE = "rolling_code_enable"
+
+# A captured packet lets a guessed key be checked offline, so the key text is stretched to make each guess costly.
+# Both ends derive the same key from the same text, so the salt is fixed; it keeps tables built for other uses of
+# PBKDF2 from applying here.
+KEY_SALT = b"esphome packet_interface xxtea"
+KEY_ITERATIONS = 600_000
+
+# The check word, and with the rolling code the boot numbers and counter
+CHECK_SIZE = 4
+ROLLING_SIZE = 12
+
+XxteaEncryption = packet_interface_ns.class_("XxteaEncryption", PacketInterface)
+
+XXTEA_SCHEMA = cv.Schema(
+    {
+        cv.GenerateID(): cv.declare_id(XxteaEncryption),
+        cv.Required(CONF_KEY): cv.All(cv.sensitive(cv.string), cv.Length(min=1)),
+        cv.Optional(CONF_ROLLING_CODE_ENABLE, default=False): cv.boolean,
+    }
+).extend(cv.COMPONENT_SCHEMA)
+
+
+def derive_key(text: str) -> list[int]:
+    """The 256-bit key for the key text, as 32-bit words in little endian order."""
+    digest = hashlib.pbkdf2_hmac("sha256", text.encode(), KEY_SALT, KEY_ITERATIONS)
+    return [int.from_bytes(digest[i : i + 4], "little") for i in range(0, 32, 4)]
+
+
+# The rolling code keeps the last counter of one peer, and accepts a packet only once the peer has sent back this
+# device's boot number
+@ENCRYPTION.register(
+    "xxtea",
+    schema=XXTEA_SCHEMA,
+    single_peer=lambda config: config[CONF_ROLLING_CODE_ENABLE],
+    needs_session=lambda config: config[CONF_ROLLING_CODE_ENABLE],
+    auto_load=lambda config: ["xxtea"],
+    # XXTEA works on whole 32-bit words
+    packet_size=lambda config, size: remaining_packet_size(
+        size & ~3,
+        CHECK_SIZE + (ROLLING_SIZE if config[CONF_ROLLING_CODE_ENABLE] else 0),
+    ),
+)
+async def build_xxtea(config: ConfigType, lower: MockObj) -> MockObj:
+    cg.add_define("USE_PACKET_INTERFACE_XXTEA")
+    var = cg.new_Pvariable(config[CONF_ID], lower, config[CONF_ROLLING_CODE_ENABLE])
+    cg.add(var.set_key(derive_key(config[CONF_KEY])))
+    await cg.register_component(var, config)
+    return var

esphome/components/packet_interface/listen_before_talk.h

@@ -0,0 +1,45 @@
+#pragma once
+
+#include <cstdint>
+
+namespace esphome::packet_interface {
+
+/**
+ * Decides whether a half-duplex radio link may send while its radio reports that it is receiving a packet.
+ *
+ * Sending is refused while the radio is busy, so the packet being received is not lost. A busy period starts when a
+ * send first finds the radio busy, and ends when a send finds it free or end_busy() is called. Once a busy period has
+ * lasted max_busy_ms, sends go ahead, so a busy flag that never clears cannot stop sending for good, however often
+ * sends are tried. Code generation sets max_busy_ms from the time the radio takes to receive the largest packet.
+ */
+class ListenBeforeTalk {
+ public:
+  static constexpr uint32_t DEFAULT_MAX_BUSY_MS = 2000;
+
+  void set_max_busy(uint32_t max_busy_ms) { this->max_busy_ms_ = max_busy_ms; }
+  uint32_t get_max_busy() const { return this->max_busy_ms_; }
+
+  /// True if a packet may be sent at \p now; \p busy says whether the radio is receiving.
+  bool may_send(bool busy, uint32_t now) {
+    if (!busy) {
+      this->busy_ = false;
+      return true;
+    }
+    if (!this->busy_) {
+      this->busy_ = true;
+      this->busy_since_ms_ = now;
+    }
+    return now - this->busy_since_ms_ >= this->max_busy_ms_;
+  }
+  /// Ends the busy period, when the radio is seen to be free other than by a send.
+  void end_busy() { this->busy_ = false; }
+  /// How long the current busy period has lasted at \p now.
+  uint32_t busy_for(uint32_t now) const { return now - this->busy_since_ms_; }
+
+ protected:
+  uint32_t busy_since_ms_{0};
+  uint32_t max_busy_ms_{DEFAULT_MAX_BUSY_MS};
+  bool busy_{false};
+};
+
+}  // namespace esphome::packet_interface

esphome/components/packet_interface/packet_transport/__init__.py

@@ -7,7 +7,12 @@ from esphome.components.packet_transport import (
 import esphome.config_validation as cv
 from esphome.types import ConfigType
 
-from .. import CONF_PACKET_INTERFACE, PacketInterface, packet_interface_ns
+from .. import (
+    CONF_PACKET_INTERFACE,
+    PacketInterface,
+    final_validate_interface,
+    packet_interface_ns,
+)
 
 CODEOWNERS = ["@clydebarrow"]
 DEPENDENCIES = ["packet_interface"]
@@ -22,6 +27,8 @@ CONFIG_SCHEMA = transport_schema(PacketInterfaceTransport).extend(
     }
 )
 
+FINAL_VALIDATE_SCHEMA = final_validate_interface(CONF_PACKET_INTERFACE)
+
 
 async def to_code(config: ConfigType) -> None:
     interface = await cg.get_variable(config[CONF_PACKET_INTERFACE])

esphome/components/packet_interface/radio_link.cpp

@@ -0,0 +1,54 @@
+#include "radio_link.h"
+#include <cinttypes>
+#include "esphome/core/application.h"
+#include "esphome/core/log.h"
+
+namespace esphome::packet_interface {
+
+ESPHOME_LOG_TAG(TAG, "packet_interface.radio");
+
+bool RadioLinkBase::check_size_(size_t size) const {
+  if (size <= this->max_packet_size_)
+    return true;
+  ESP_LOGW(TAG, "Packet of %zu bytes is larger than %zu", size, this->max_packet_size_);
+  return false;
+}
+
+bool RadioLinkBase::may_send_(bool busy) {
+  uint32_t now = App.get_loop_component_start_time();
+  if (busy)
+    this->enable_loop();
+  if (!this->listen_before_talk_.may_send(busy, now))
+    return false;
+  if (busy) {
+    // The limit is longer than any packet takes, so the radio's busy indication is stuck or the channel is jammed
+    ESP_LOGW(TAG, "Radio busy for %" PRIu32 "ms, sending anyway", this->listen_before_talk_.busy_for(now));
+  }
+  return true;
+}
+
+bool RadioLinkBase::skip_empty_() const {
+  ESP_LOGV(TAG, "Empty packet not sent");
+  return true;
+}
+
+void RadioLinkBase::radio_not_ready_(bool failed) {
+  if (!failed || this->failed_warned_)
+    return;
+  this->failed_warned_ = true;
+  ESP_LOGW(TAG, "%s: The radio failed to set up, so nothing can be sent", this->name_);
+}
+
+void RadioLinkBase::radio_free_() {
+  this->listen_before_talk_.end_busy();
+  this->disable_loop();
+}
+
+void RadioLinkBase::receive_(const std::vector<uint8_t> &packet, float rssi, float snr) {
+  PacketMetaData meta_data;
+  meta_data.rssi = rssi;
+  meta_data.snr = snr;
+  this->on_receive_from_interface_(PacketBuffer(packet.data(), packet.size()), meta_data);
+}
+
+}  // namespace esphome::packet_interface

esphome/components/packet_interface/radio_link.h

@@ -0,0 +1,87 @@
+#pragma once
+
+#include <vector>
+
+#include "esphome/components/packet_interface/listen_before_talk.h"
+#include "esphome/components/packet_interface/packet_interface.h"
+
+namespace esphome::packet_interface {
+
+/// The parts of RadioLink that do not depend on the radio.
+class RadioLinkBase : public PacketInterface {
+ public:
+  void set_max_busy(uint32_t max_busy_ms) { this->listen_before_talk_.set_max_busy(max_busy_ms); }
+
+ protected:
+  explicit RadioLinkBase(size_t max_packet_size) : PacketInterface(max_packet_size) {}
+  /// False if a packet of this size is too large.
+  bool check_size_(size_t size) const;
+  /// False if sending must wait, as the radio is busy; starts loop() to watch the radio.
+  bool may_send_(bool busy);
+  /// Returns true for an empty packet, which the radios cannot send, so there is nothing to retry.
+  bool skip_empty_() const;
+  /// Warns once when a send finds the radio failed; until its setup has run, sends are refused quietly.
+  void radio_not_ready_(bool failed);
+  /// Ends the busy period when loop() finds the radio free.
+  void radio_free_();
+  void receive_(const std::vector<uint8_t> &packet, float rssi, float snr);
+
+  ListenBeforeTalk listen_before_talk_;
+  bool failed_warned_{false};
+};
+
+/**
+ * A packet interface link over a packet radio: each packet is one radio packet, with the RSSI and SNR of received
+ * packets in the metadata. Sending waits for the radio to finish transmitting. A radio cannot hear while it sends, so
+ * sending is refused while the radio is receiving a packet. A reliability layer sends the packet again shortly, and
+ * entity_transport after a delay; other callers drop it, logging at debug level at most. While a busy period lasts,
+ * loop() watches the radio and ends the period as soon as the radio is free, so a later reception starts a new one.
+ *
+ * Radio provides is_receiving(), register_listener(Listener *) and transmit_packet(const uint8_t *, size_t), which
+ * returns Error::NONE on success. Listener declares on_packet(packet, rssi, snr). MaxPacketSize is the radio's limit.
+ */
+template<typename Radio, typename Listener, typename Error, size_t MaxPacketSize>
+class RadioLink : public RadioLinkBase, public Listener {
+ public:
+  RadioLink(Radio *radio, size_t max_packet_size) : RadioLinkBase(max_packet_size), radio_(radio) {}
+
+  void setup() override {
+    this->radio_->register_listener(this);
+    this->disable_loop();
+  }
+  // Runs only during a busy period; a busy flag that never clears keeps it running. A radio that failed meanwhile
+  // is not read again, as reading it may wait on the radio every time
+  void loop() override {
+    if (!this->radio_->is_ready() || !this->radio_->is_receiving())
+      this->radio_free_();
+  }
+
+  bool send_to_interface(const PacketBuffer &data, const PacketMetaData &meta_data) override {
+    // The radio is set up after the layers above, which may send from their own setup
+    if (!this->radio_->is_ready()) {
+      this->radio_not_ready_(this->radio_->is_failed());
+      return false;
+    }
+    size_t size = data.size();
+    if (size == 0)
+      return this->skip_empty_();
+    if (!this->check_size_(size) || !this->may_send_(this->radio_->is_receiving()))
+      return false;
+    if (data.is_contiguous()) {
+      auto span = data.as_span();
+      return this->radio_->transmit_packet(span.data(), span.size()) == Error::NONE;
+    }
+    uint8_t buf[MaxPacketSize];
+    data.copy_to(buf, size);
+    return this->radio_->transmit_packet(buf, size) == Error::NONE;
+  }
+
+  void on_packet(const std::vector<uint8_t> &packet, float rssi, float snr) override {
+    this->receive_(packet, rssi, snr);
+  }
+
+ protected:
+  Radio *radio_;
+};
+
+}  // namespace esphome::packet_interface

esphome/components/packet_interface/radio_link.py

@@ -0,0 +1,138 @@
+"""Shared code generation for the packet interface links over packet radios, such as the SX126x and SX127x."""
+
+from collections.abc import Callable
+import math
+
+import esphome.codegen as cg
+from esphome.components.const import CONF_MAX_PACKET_SIZE
+import esphome.config_validation as cv
+from esphome.const import CONF_ID
+from esphome.core import CORE, EsphomeError
+from esphome.cpp_generator import MockObjClass
+import esphome.final_validate as fv
+from esphome.types import ConfigType
+
+from . import new_packet_interface, packet_interface_schema
+from .layers import CONF_ADDRESSING, CONF_PEERS, STACK_ORDER
+
+# The radios' payload length register is 8 bits
+MAX_PACKET_SIZE = 255
+
+# Listen before talk holds a send back for at most the airtime of the largest packet, and never less than this
+MIN_MAX_BUSY_MS = 2000
+# Room for the preamble detection and the radio's own delays
+MARGIN = 1.25
+
+
+def packet_airtime_ms(radio: ConfigType, size: int) -> float:
+    """The time a radio configured as in radio takes to send a packet of size bytes.
+
+    LoRa follows the Semtech formula for an explicit header; the low data rate optimization is assumed when a symbol
+    takes more than 16 ms, as the drivers enable it. Other modulations count the preamble, sync word, length byte,
+    payload and CRC at the bitrate, treating the preamble size as bytes, which gives the longer time.
+    """
+    if str(radio["modulation"]) == "LORA":
+        spreading_factor = radio["spreading_factor"]
+        bandwidth_hz = (
+            float(str(radio["bandwidth"]).removesuffix("kHz").replace("_", ".")) * 1000
+        )
+        coding_rate = int(str(radio["coding_rate"])[-1]) - 4
+        symbol_s = (1 << spreading_factor) / bandwidth_hz
+        low_data_rate = 1 if symbol_s > 0.016 else 0
+        crc = 16 if radio.get("crc_enable", False) else 0
+        payload_symbols = 8 + max(
+            math.ceil(
+                (8 * size - 4 * spreading_factor + 28 + crc)
+                / (4 * (spreading_factor - 2 * low_data_rate))
+            )
+            * (coding_rate + 4),
+            0,
+        )
+        return (radio["preamble_size"] + 4.25 + payload_symbols) * symbol_s * 1000
+    bytes_sent = (
+        radio["preamble_size"] + len(radio.get("sync_value", [])) + 1 + size + 2
+    )
+    return bytes_sent * 8 / radio["bitrate"] * 1000
+
+
+def max_busy_ms(radio: ConfigType, max_packet_size: int) -> int:
+    """How long listen before talk may hold a send back."""
+    return max(
+        MIN_MAX_BUSY_MS, math.ceil(packet_airtime_ms(radio, max_packet_size) * MARGIN)
+    )
+
+
+def radio_link_schema(
+    class_: MockObjClass, radio_id_key: str, radio_class: MockObjClass
+) -> cv.Schema:
+    """Schema for a radio link, referring to its radio by radio_id_key."""
+    return packet_interface_schema(class_, MAX_PACKET_SIZE, MAX_PACKET_SIZE).extend(
+        {cv.GenerateID(radio_id_key): cv.use_id(radio_class)}
+    )
+
+
+def _radio_config(config: ConfigType, radio_id_key: str) -> ConfigType:
+    full_config = fv.full_config.get()
+    return full_config.get_config_for_path(
+        full_config.get_path_for_id(config[radio_id_key])[:-1]
+    )
+
+
+def _two_way_layer(config: ConfigType) -> str | None:
+    """The first layer on the link or in a peer that keeps state for one peer, so needs packets back from it."""
+    for stack in (config, *config.get(CONF_ADDRESSING, {}).get(CONF_PEERS, [])):
+        for kind in STACK_ORDER:
+            if (layer := stack.get(kind.key)) is not None and kind.get_type(
+                layer
+            ).single_peer(layer):
+                return kind.key
+    return None
+
+
+def radio_link_final_validate(
+    radio_id_key: str,
+    payload_length_key: str,
+    rx_start_key: str,
+    check: Callable[[ConfigType, ConfigType], None] | None = None,
+) -> Callable[[ConfigType], ConfigType]:
+    """Final validation for a radio link: packets vary in length, the radio listens after sending when a layer needs
+    replies, and check(link, radio) checks the rest.
+    """
+
+    def validator(config: ConfigType) -> ConfigType:
+        radio = _radio_config(config, radio_id_key)
+        if radio[payload_length_key] != 0:
+            raise cv.Invalid(
+                f"Packets vary in length, so the radio's '{payload_length_key}' must be 0",
+                path=[radio_id_key],
+            )
+        if not radio[rx_start_key] and (layer := _two_way_layer(config)) is not None:
+            raise cv.Invalid(
+                f"This '{layer}' needs packets from the peer, but the radio sleeps after sending unless "
+                f"'{rx_start_key}' is true",
+                path=[radio_id_key],
+            )
+        if check is not None:
+            check(config, radio)
+        return config
+
+    return validator
+
+
+async def new_radio_link(
+    config: ConfigType, radio_id_key: str, radio_domain: str
+) -> None:
+    """Create a radio link, with its listen before talk limit worked out from the radio's settings."""
+    radio = await cg.get_variable(config[radio_id_key])
+    var = await new_packet_interface(config, radio, config[CONF_MAX_PACKET_SIZE])
+    radio_config = next(
+        (
+            conf
+            for conf in CORE.config[radio_domain]
+            if conf[CONF_ID] == config[radio_id_key]
+        ),
+        None,
+    )
+    if radio_config is None:
+        raise EsphomeError(f"No {radio_domain} radio with id '{config[radio_id_key]}'")
+    cg.add(var.set_max_busy(max_busy_ms(radio_config, config[CONF_MAX_PACKET_SIZE])))

esphome/components/packet_interface/xxtea_encryption.cpp

@@ -0,0 +1,182 @@
+#include "xxtea_encryption.h"
+#ifdef USE_PACKET_INTERFACE_XXTEA
+#include <algorithm>
+#include <cstring>
+#include "esphome/components/xxtea/xxtea.h"
+#include "esphome/core/helpers.h"
+#include "esphome/core/log.h"
+
+namespace esphome::packet_interface {
+
+ESPHOME_LOG_TAG(TAG, "packet_interface.xxtea");
+
+static constexpr uint32_t PREF_HASH = fnv1a_hash("packet_interface.xxtea");
+// Different for each mode, so devices set up differently drop each other's packets
+static constexpr uint8_t CHECK_BYTES[3] = {0x58, 0x54, 0x45};
+static constexpr uint8_t ROLLING_CHECK_BYTES[3] = {0x58, 0x54, 0x52};
+static constexpr size_t CHECK_SIZE = 4;
+// Boot number, counter, and the echo of the receiver's boot number
+static constexpr size_t ROLLING_SIZE = 12;
+// XXTEA needs at least two words
+static constexpr size_t MIN_LENGTH = 8;
+static constexpr size_t MAX_PADDING = 4;
+
+static void put_uint32(uint8_t *buf, uint32_t value) {
+  buf[0] = value;
+  buf[1] = value >> 8;
+  buf[2] = value >> 16;
+  buf[3] = value >> 24;
+}
+
+static uint32_t get_uint32(const uint8_t *buf) { return encode_uint32(buf[3], buf[2], buf[1], buf[0]); }
+
+static constexpr size_t trailer_size(bool rolling_code) {
+  return rolling_code ? ROLLING_SIZE + CHECK_SIZE : CHECK_SIZE;
+}
+
+XxteaEncryption::XxteaEncryption(PacketInterface *lower, bool rolling_code)
+    // XXTEA works on whole 32-bit words
+    : PacketInterface(remaining_packet_size(lower->get_max_packet_size() & ~size_t{3}, trailer_size(rolling_code))),
+      lower_(lower),
+      trailer_size_(trailer_size(rolling_code)),
+      rolling_code_(rolling_code) {
+  this->stack_on_(lower, CAPABILITY_ENCRYPTION);
+}
+
+void XxteaEncryption::set_key(std::initializer_list<uint32_t> key) {
+  std::copy_n(key.begin(), std::min(key.size(), this->key_.size()), this->key_.begin());
+}
+
+void XxteaEncryption::setup() {
+  if (this->max_packet_size_ == 0) {
+    this->mark_failed(LOG_STR("max_packet_size too small for the configured layers"));
+    return;
+  }
+  size_t words = this->lower_->get_max_packet_size() / 4;
+  RAMAllocator<uint32_t> allocator;
+  this->tx_buffer_ = allocator.allocate(words * 2);
+  if (this->tx_buffer_ == nullptr) {
+    this->mark_failed(LOG_STR("Not enough memory for the packet buffers"));
+    return;
+  }
+  this->rx_buffer_ = this->tx_buffer_ + words;
+  if (this->rolling_code_) {
+    this->pref_ = global_preferences->make_preference<uint32_t>(fnv1a_hash_extend(PREF_HASH, this->name_), true);
+    this->pref_.load(&this->boot_);
+    this->next_boot_();
+  }
+  this->lower_->add_packet_interface_listener(
+      [this](const PacketBuffer &data, const PacketMetaData &meta_data) { this->receive_(data, meta_data); });
+}
+
+void XxteaEncryption::dump_config() {
+  ESP_LOGCONFIG(TAG,
+                "XXTEA Encryption on '%s':\n"
+                "  Max Packet Size: %zu\n"
+                "  Rolling Code: %s",
+                this->name_, this->max_packet_size_, YESNO(this->rolling_code_));
+  if (this->rolling_code_) {
+    ESP_LOGCONFIG(TAG, "  Boot Number: %" PRIu32, this->boot_);
+  }
+}
+
+// A new boot number must be saved before it is used, or a crash could make the peer see it again
+void XxteaEncryption::next_boot_() {
+  this->boot_++;
+  this->counter_ = 0;
+  if (!this->pref_.save(&this->boot_) || !global_preferences->sync()) {
+    ESP_LOGW(TAG, "%s: Could not save the boot number, so a restart could reuse it", this->name_);
+  }
+}
+
+bool XxteaEncryption::send_to_interface(const PacketBuffer &data, const PacketMetaData &meta_data) {
+  if (this->tx_buffer_ == nullptr)
+    return false;
+  size_t size = data.size();
+  if (size > this->max_packet_size_) {
+    ESP_LOGW(TAG, "%s: Packet of %zu bytes is larger than %zu", this->name_, size, this->max_packet_size_);
+    return false;
+  }
+  size_t padding = (4 - (size + this->trailer_size_) % 4) % 4;
+  if (size + padding + this->trailer_size_ < MIN_LENGTH)
+    padding += 4;
+  size_t length = size + padding + this->trailer_size_;
+  auto *buf = reinterpret_cast<uint8_t *>(this->tx_buffer_);
+  data.copy_to(buf, size);
+  memset(buf + size, 0, padding);
+  uint8_t *check = buf + length - CHECK_SIZE;
+  if (this->rolling_code_) {
+    put_uint32(check - ROLLING_SIZE, this->boot_);
+    put_uint32(check - ROLLING_SIZE + 4, this->counter_);
+    put_uint32(check - ROLLING_SIZE + 8, this->echo_boot_);
+    memcpy(check, ROLLING_CHECK_BYTES, sizeof(ROLLING_CHECK_BYTES));
+    if (++this->counter_ == 0)
+      this->next_boot_();
+  } else {
+    memcpy(check, CHECK_BYTES, sizeof(CHECK_BYTES));
+  }
+  check[CHECK_SIZE - 1] = padding;
+  xxtea::encrypt(this->tx_buffer_, length / 4, this->key_.data());
+  return this->lower_->send_to_interface(PacketBuffer(buf, length), meta_data);
+}
+
+bool XxteaEncryption::accept_counter_(uint32_t boot, uint32_t counter) {
+  if (this->peer_seen_ && (boot < this->peer_boot_ || (boot == this->peer_boot_ && counter <= this->peer_counter_)))
+    return false;
+  this->peer_seen_ = true;
+  this->peer_boot_ = boot;
+  this->peer_counter_ = counter;
+  return true;
+}
+
+void XxteaEncryption::receive_(const PacketBuffer &data, const PacketMetaData &meta_data) {
+  size_t length = data.size();
+  if (length % 4 != 0 || length < std::max(MIN_LENGTH, this->trailer_size_) ||
+      length > this->lower_->get_max_packet_size()) {
+    ESP_LOGV(TAG, "%s: Packet of %zu bytes dropped", this->name_, length);
+    this->note_received_(false);
+    return;
+  }
+  auto *buf = reinterpret_cast<uint8_t *>(this->rx_buffer_);
+  data.copy_to(buf, length);
+  xxtea::decrypt(this->rx_buffer_, length / 4, this->key_.data());
+  const uint8_t *check = buf + length - CHECK_SIZE;
+  const uint8_t *expected = this->rolling_code_ ? ROLLING_CHECK_BYTES : CHECK_BYTES;
+  size_t padding = check[CHECK_SIZE - 1];
+  if (memcmp(check, expected, sizeof(CHECK_BYTES)) != 0 || padding > MAX_PADDING ||
+      padding > length - this->trailer_size_) {
+    ESP_LOGV(TAG, "%s: Packet failed authentication", this->name_);
+    this->note_received_(false);
+    return;
+  }
+  this->note_received_(true);
+  if (this->rolling_code_) {
+    uint32_t boot = get_uint32(check - ROLLING_SIZE);
+    uint32_t counter = get_uint32(check - ROLLING_SIZE + 4);
+    uint32_t echo = get_uint32(check - ROLLING_SIZE + 8);
+    // Learn the peer's boot number even from a packet that is then dropped, so both sides can catch up
+    if (boot > this->echo_boot_)
+      this->echo_boot_ = boot;
+    // A packet recorded before this boot cannot carry this boot's number
+    if (echo != this->boot_) {
+      ESP_LOGV(TAG, "%s: Packet for boot %" PRIu32 " dropped", this->name_, echo);
+      return;
+    }
+    if (!this->accept_counter_(boot, counter)) {
+      // A boot number lower than one already heard means the peer lost its saved boot number, or a replay
+      if (boot < this->peer_boot_ && !this->old_boot_warned_) {
+        this->old_boot_warned_ = true;
+        ESP_LOGW(TAG,
+                 "%s: Packets from an older boot %" PRIu32 " of the peer are dropped; if its flash was erased, "
+                 "restart this device",
+                 this->name_, boot);
+      }
+      ESP_LOGV(TAG, "%s: Old packet %" PRIu32 ":%" PRIu32 " dropped", this->name_, boot, counter);
+      return;
+    }
+  }
+  this->on_receive_from_interface_(PacketBuffer(buf, length - this->trailer_size_ - padding), meta_data);
+}
+
+}  // namespace esphome::packet_interface
+#endif

esphome/components/packet_interface/xxtea_encryption.h

@@ -0,0 +1,61 @@
+#pragma once
+
+#include "esphome/core/defines.h"
+#ifdef USE_PACKET_INTERFACE_XXTEA
+#include <array>
+#include <initializer_list>
+
+#include "esphome/core/preferences.h"
+#include "packet_interface.h"
+
+namespace esphome::packet_interface {
+
+/**
+ * An encryption layer that encrypts and authenticates each packet with XXTEA and a 256-bit shared key.
+ *
+ * The packet is padded with zeros and followed by a trailer, then the whole is encrypted as one block. With the
+ * rolling code enabled, the trailer starts with:
+ * - a 32-bit boot number, saved in flash and increased at every boot;
+ * - a 32-bit packet counter, starting at 0 at every boot;
+ * - the highest boot number heard from the peer, echoed back to it.
+ * The trailer always ends with 3 fixed check bytes and the number of padding bytes. XXTEA mixes the whole block, so
+ * a packet that was changed or encrypted with another key fails the check.
+ * With the rolling code, a packet is dropped as a replay unless it echoes this device's current boot number, and its
+ * boot number and counter are higher than those of the last packet accepted from the peer. A boot number is never
+ * reused, so the echo acts as a fresh challenge after every restart.
+ */
+class XxteaEncryption : public PacketInterface {
+ public:
+  XxteaEncryption(PacketInterface *lower, bool rolling_code);
+
+  void setup() override;
+  void dump_config() override;
+  bool send_to_interface(const PacketBuffer &data, const PacketMetaData &meta_data) override;
+
+  void set_key(std::initializer_list<uint32_t> key);
+
+ protected:
+  void receive_(const PacketBuffer &data, const PacketMetaData &meta_data);
+  bool accept_counter_(uint32_t boot, uint32_t counter);
+  void next_boot_();
+
+  PacketInterface *lower_;
+  const size_t trailer_size_;
+  std::array<uint32_t, 8> key_{};
+  // Separate buffers, as a layer above may send a reply while a received packet is being passed up; both are in one
+  // block allocated in setup(), and tx_buffer_ stays null if that fails
+  uint32_t *tx_buffer_{nullptr};
+  uint32_t *rx_buffer_{nullptr};
+  ESPPreferenceObject pref_;
+  uint32_t boot_{0};
+  uint32_t counter_{0};
+  uint32_t peer_boot_{0};
+  uint32_t peer_counter_{0};
+  uint32_t echo_boot_{0};  // highest boot number heard from the peer
+  bool peer_seen_{false};
+  bool old_boot_warned_{false};
+  const bool rolling_code_;
+};
+
+}  // namespace esphome::packet_interface
+#endif

esphome/components/pca6416a/pca6416a.cpp

@@ -1,5 +1,4 @@
 #include "pca6416a.h"
-#include "esphome/core/helpers.h"
 #include "esphome/core/log.h"
 
 namespace esphome::pca6416a {
@@ -171,7 +170,11 @@ void PCA6416AComponent::update_register_(uint8_t pin, bool pin_value, uint8_t re
     this->read_register_(reg_addr, &reg_value);
   }
 
-  assign_bits(reg_value, 1 << bit, pin_value);
+  if (pin_value) {
+    reg_value |= 1 << bit;
+  } else {
+    reg_value &= ~(1 << bit);
+  }
 
   this->write_register_(reg_addr, reg_value);
 

esphome/components/pca9505/pca9505.cpp

@@ -1,5 +1,4 @@
 #include "pca9505.h"
-#include "esphome/core/helpers.h"
 #include "esphome/core/log.h"
 
 namespace esphome::pca9505 {
@@ -75,7 +74,11 @@ bool PCA9505Component::digital_read_cache(uint8_t pin) { return this->input_[pin
 void PCA9505Component::digital_write_hw(uint8_t pin, bool value) {
   const uint8_t bank = pin / 8;
   const uint8_t mask = 1 << (pin % 8);
-  assign_bits(this->output_[bank], mask, value);
+  if (value) {
+    this->output_[bank] |= mask;
+  } else {
+    this->output_[bank] &= ~mask;
+  }
   this->write_bank_(OUTPUT_REG, bank, this->output_[bank]);
 }
 

esphome/components/pca9554/pca9554.cpp

@@ -1,5 +1,4 @@
 #include "pca9554.h"
-#include "esphome/core/helpers.h"
 #include "esphome/core/log.h"
 
 namespace esphome::pca9554 {
@@ -100,7 +99,11 @@ bool PCA9554Component::digital_read_cache(uint8_t pin) {
 }
 
 void PCA9554Component::digital_write_hw(uint8_t pin, bool value) {
-  assign_bits(this->output_mask_, 1 << pin, value);
+  if (value) {
+    this->output_mask_ |= (1 << pin);
+  } else {
+    this->output_mask_ &= ~(1 << pin);
+  }
 #ifdef USE_PCA9554_PCAL
   if (this->write_register_(OUTPUT_REG, this->output_mask_))
     this->retry_pcal_shadows_();  // an output-only hub never reads, so it retries here

esphome/components/pcd8544/pcd_8544.cpp

@@ -90,7 +90,11 @@ void HOT PCD8544::draw_absolute_pixel_internal(int x, int y, Color color) {
 
   uint16_t pos = x + (y / 8) * this->get_width_internal();
   uint8_t subpos = y % 8;
-  assign_bits(this->buffer_[pos], 1 << subpos, color.is_on());
+  if (color.is_on()) {
+    this->buffer_[pos] |= (1 << subpos);
+  } else {
+    this->buffer_[pos] &= ~(1 << subpos);
+  }
 }
 
 void PCD8544::dump_config() {

esphome/components/pcf8574/pcf8574.cpp

@@ -60,7 +60,11 @@ bool PCF8574Component::digital_read_hw(uint8_t pin) {
 bool PCF8574Component::digital_read_cache(uint8_t pin) { return this->input_mask_ & (1 << pin); }
 
 void PCF8574Component::digital_write_hw(uint8_t pin, bool value) {
-  assign_bits(this->output_mask_, 1 << pin, value);
+  if (value) {
+    this->output_mask_ |= (1 << pin);
+  } else {
+    this->output_mask_ &= ~(1 << pin);
+  }
   this->write_gpio_();
 }
 void PCF8574Component::pin_mode(uint8_t pin, gpio::Flags flags) {

esphome/components/pi4ioe5v6408/pi4ioe5v6408.cpp

@@ -1,5 +1,4 @@
 #include "pi4ioe5v6408.h"
-#include "esphome/core/helpers.h"
 #include "esphome/core/log.h"
 
 namespace esphome::pi4ioe5v6408 {
@@ -130,7 +129,11 @@ void PI4IOE5V6408Component::digital_write_hw(uint8_t pin, bool value) {
   if (this->is_failed())
     return;
 
-  assign_bits(this->output_mask_, 1 << pin, value);
+  if (value) {
+    this->output_mask_ |= (1 << pin);
+  } else {
+    this->output_mask_ &= ~(1 << pin);
+  }
   if (!this->status_comm_result(this->write_byte(PI4IOE5V6408_REGISTER_OUT_SET, this->output_mask_),
                                 LOG_STR("Failed to write output register")))
     return;

esphome/components/runtime_image/runtime_image.cpp

@@ -1,6 +1,5 @@
 #include "runtime_image.h"
 #include "image_decoder.h"
-#include "esphome/core/helpers.h"
 #include "esphome/core/log.h"
 #include <algorithm>
 #include <cstdint>
@@ -92,7 +91,11 @@ void RuntimeImage::draw_pixel(int x, int y, const Color &color) {
       auto on = is_color_on(color);
       if (this->has_transparency() && color.w < 0x80)
         on = false;
-      assign_bits(this->buffer_[pos], bitno, on);
+      if (on) {
+        this->buffer_[pos] |= bitno;
+      } else {
+        this->buffer_[pos] &= ~bitno;
+      }
       break;
     }
     case image::IMAGE_TYPE_RGB111: {

esphome/components/ssd1306_base/ssd1306_base.cpp

@@ -342,7 +342,11 @@ void HOT SSD1306::draw_absolute_pixel_internal(int x, int y, Color color) {
 
   uint16_t pos = x + (y / 8) * this->get_width_internal();
   uint8_t subpos = y & 0x07;
-  assign_bits(this->buffer_[pos], 1 << subpos, color.is_on());
+  if (color.is_on()) {
+    this->buffer_[pos] |= (1 << subpos);
+  } else {
+    this->buffer_[pos] &= ~(1 << subpos);
+  }
 }
 void SSD1306::fill(Color color) {
   // If clipping is active, fall back to base implementation

esphome/components/st7305/display.py

@@ -53,13 +53,6 @@ MODELS = DriverChip.get_models()
 DEFAULT_MODEL = "WAVESHARE-400X300"
 
 
-def _model_key(model: DriverChip, key: str) -> cv.Optional | cv.Required:
-    """Default the key from the model, or require it when the model has none."""
-    if model.get_default(key, None) is None:
-        return cv.Required(key)
-    return model.option(key)
-
-
 def _model_schema(model: DriverChip) -> cv.Schema:
     iseqconf = (
         cv.Required(CONF_INIT_SEQUENCE)
@@ -79,12 +72,12 @@ def _model_schema(model: DriverChip) -> cv.Schema:
             {
                 cv.GenerateID(): cv.declare_id(ST7305),
                 cv.Required(CONF_MODEL): cv.one_of(*MODELS, upper=True),
-                _model_key(model, CONF_CS_PIN): pins.gpio_output_pin_schema,
-                _model_key(model, CONF_DC_PIN): pins.gpio_output_pin_schema,
+                model.option(CONF_CS_PIN, cv.UNDEFINED): pins.gpio_output_pin_schema,
+                model.option(CONF_DC_PIN, cv.UNDEFINED): pins.gpio_output_pin_schema,
                 model.option(CONF_RESET_PIN, cv.UNDEFINED): pins.gpio_output_pin_schema,
-                _model_key(model, CONF_WIDTH): cv.int_range(min=8, max=1024),
-                _model_key(model, CONF_HEIGHT): cv.int_range(min=8, max=1024),
-                _model_key(model, CONF_PORTRAIT): cv.boolean,
+                cv.Optional(CONF_WIDTH): cv.int_range(min=8, max=1024),
+                cv.Optional(CONF_HEIGHT): cv.int_range(min=8, max=1024),
+                cv.Optional(CONF_PORTRAIT): cv.boolean,
                 cv.Optional(CONF_COLUMN_START): cv.int_range(min=0, max=255),
                 cv.Optional(CONF_COLUMN_END): cv.int_range(min=0, max=255),
                 cv.Optional(CONF_ROW_START): cv.int_range(min=0, max=255),
@@ -96,9 +89,23 @@ def _model_schema(model: DriverChip) -> cv.Schema:
 
 
 def _resolve(config: ConfigType, model: DriverChip) -> None:
-    """Derive and validate the address window, and default the init sequence."""
-    width = config[CONF_WIDTH]
-    height = config[CONF_HEIGHT]
+    """Fill in model defaults and validate the geometry and address window."""
+    if (width := config.get(CONF_WIDTH)) is None:
+        if (width := model.get_default(CONF_WIDTH, None)) is None:
+            raise cv.Invalid("'width' is required for this model", path=[CONF_WIDTH])
+        config[CONF_WIDTH] = width
+    if (height := config.get(CONF_HEIGHT)) is None:
+        if (height := model.get_default(CONF_HEIGHT, None)) is None:
+            raise cv.Invalid("'height' is required for this model", path=[CONF_HEIGHT])
+        config[CONF_HEIGHT] = height
+
+    if config.get(CONF_PORTRAIT) is None:
+        if (default := model.get_default(CONF_PORTRAIT, None)) is None:
+            raise cv.Invalid(
+                "'portrait' is required for this model", path=[CONF_PORTRAIT]
+            )
+        config[CONF_PORTRAIT] = default
+
     if config[CONF_PORTRAIT]:
         if width % 12 or height % 2:
             raise cv.Invalid(
@@ -145,6 +152,10 @@ def _resolve(config: ConfigType, model: DriverChip) -> None:
     if config.get(CONF_INIT_SEQUENCE) is None:
         config[CONF_INIT_SEQUENCE] = model.initsequence
 
+    for key, label in ((CONF_CS_PIN, "cs_pin"), (CONF_DC_PIN, "dc_pin")):
+        if key not in config:
+            raise cv.Invalid(f"'{label}' is required for this model", path=[key])
+
 
 def model_schema(config: ConfigType) -> cv.Schema:
     """Return the schema for the model selected in the config."""

esphome/components/st7305/st7305.cpp

@@ -1,8 +1,8 @@
 #include "st7305.h"
 
 #include <algorithm>
+#include <cstring>
 
-#include "esphome/core/helpers.h"
 #include "esphome/core/log.h"
 
 namespace esphome::st7305 {
@@ -27,6 +27,7 @@ bool ST7305::init_buffer_() {
     this->mark_failed(LOG_STR("Buffer allocation failed"));
     return false;
   }
+  memset(this->buffer_, 0x00, this->buffer_length_);
   this->clear_dirty_();
   return true;
 }
@@ -190,7 +191,11 @@ void HOT ST7305::draw_absolute_pixel_internal(int x, int y, Color color) {
   // The init sequence enables INVON, so a set bit is white and a clear bit is black.
   uint8_t &value = this->buffer_[index];
   const uint8_t previous = value;
-  assign_bits(value, mask, color.is_on());
+  if (color.is_on()) {
+    value |= mask;
+  } else {
+    value &= ~mask;
+  }
   if (value == previous)
     return;
   this->extend_dirty_(x, y, x, y);

esphome/components/st7567_base/st7567_base.cpp

@@ -123,7 +123,11 @@ void HOT ST7567::draw_absolute_pixel_internal(int x, int y, Color color) {
 
   uint16_t pos = x + (y / 8) * this->get_width_internal();
   uint8_t subpos = y & 0x07;
-  assign_bits(this->buffer_[pos], 1 << subpos, color.is_on());
+  if (color.is_on()) {
+    this->buffer_[pos] |= (1 << subpos);
+  } else {
+    this->buffer_[pos] &= ~(1 << subpos);
+  }
 }
 
 void ST7567::fill(Color color) {

esphome/components/sx126x/packet_interface/__init__.py

@@ -0,0 +1,50 @@
+from esphome.components import packet_interface
+from esphome.components.packet_interface.radio_link import (
+    new_radio_link,
+    radio_link_final_validate,
+    radio_link_schema,
+)
+import esphome.config_validation as cv
+from esphome.types import ConfigType
+
+from .. import (
+    CONF_MODULATION,
+    CONF_PAYLOAD_LENGTH,
+    CONF_RX_START,
+    CONF_SX126X_ID,
+    CONF_SYNC_VALUE,
+    DOMAIN,
+    SX126x,
+    SX126xListener,
+    sx126x_ns,
+)
+
+CODEOWNERS = ["@clydebarrow"]
+DEPENDENCIES = ["sx126x"]
+
+SX126xPacketInterface = sx126x_ns.class_(
+    "SX126xPacketInterface", packet_interface.PacketInterface, SX126xListener
+)
+
+CONFIG_SCHEMA = radio_link_schema(SX126xPacketInterface, CONF_SX126X_ID, SX126x)
+
+
+def _check_fsk(config: ConfigType, radio: ConfigType) -> None:
+    """Without LoRa, the radio can tell that a packet is arriving only from its sync word, which listen before talk
+    needs.
+    """
+    if radio[CONF_MODULATION] != "LORA" and not radio[CONF_SYNC_VALUE]:
+        raise cv.Invalid(
+            f"Without LoRa modulation the radio needs a '{CONF_SYNC_VALUE}', so that the link can tell when a packet "
+            "is arriving and not send over it",
+            path=[CONF_SX126X_ID],
+        )
+
+
+FINAL_VALIDATE_SCHEMA = radio_link_final_validate(
+    CONF_SX126X_ID, CONF_PAYLOAD_LENGTH, CONF_RX_START, _check_fsk
+)
+
+
+async def to_code(config: ConfigType) -> None:
+    await new_radio_link(config, CONF_SX126X_ID, DOMAIN)

esphome/components/sx126x/packet_interface/sx126x_packet_interface.h

@@ -0,0 +1,10 @@
+#pragma once
+
+#include "esphome/components/packet_interface/radio_link.h"
+#include "esphome/components/sx126x/sx126x.h"
+
+namespace esphome::sx126x {
+
+using SX126xPacketInterface = packet_interface::RadioLink<SX126x, SX126xListener, SX126xError, SX126X_MAX_PACKET_SIZE>;
+
+}  // namespace esphome::sx126x

esphome/components/sx126x/sx126x.cpp

@@ -1,6 +1,7 @@
 #include "sx126x.h"
 #include "esphome/core/application.h"
 #include "esphome/core/hal.h"
+#include "esphome/core/helpers.h"
 #include "esphome/core/log.h"
 
 namespace esphome::sx126x {
@@ -402,6 +403,15 @@ void SX126x::loop() {
   }
 }
 
+bool SX126x::is_receiving() {
+  // DIO1 signals a received packet, which sending would overwrite in the radio's buffer
+  if (this->dio1_pin_->digital_read())
+    return true;
+  uint8_t buf[2];
+  this->read_opcode_(RADIO_GET_IRQSTATUS, buf, 2);
+  return (encode_uint16(buf[0], buf[1]) & (IRQ_HEADER_VALID | IRQ_SYNCWORD_VALID)) != 0;
+}
+
 void SX126x::run_image_cal() {
   // the following values were taken from section 9.2.1 table 9-2
   // in rev 2.1 of the datasheet
@@ -430,10 +440,11 @@ void SX126x::run_image_cal() {
 void SX126x::set_mode_rx() {
   uint8_t buf[8];
 
-  // configure irq params
+  // configure irq params; a valid header or sync word is flagged for is_receiving(), but not signalled on DIO1
   uint16_t irq = IRQ_RX_DONE | IRQ_RX_TX_TIMEOUT | IRQ_CRC_ERROR;
-  buf[0] = (irq >> 8) & 0xFF;
-  buf[1] = (irq >> 0) & 0xFF;
+  uint16_t flags = irq | IRQ_HEADER_VALID | IRQ_SYNCWORD_VALID;
+  buf[0] = (flags >> 8) & 0xFF;
+  buf[1] = (flags >> 0) & 0xFF;
   buf[2] = (irq >> 8) & 0xFF;
   buf[3] = (irq >> 0) & 0xFF;
   buf[4] = (IRQ_RADIO_NONE >> 8) & 0xFF;

esphome/components/sx126x/sx126x.h

@@ -104,6 +104,8 @@ class SX126x final : public Component,
     return this->transmit_packet(packet.data(), packet.size());
   }
   void register_listener(SX126xListener *listener) { this->listeners_.push_back(listener); }
+  /// True while a packet is being received, or has been received and not yet read; sending would lose it.
+  bool is_receiving();
   Trigger<std::vector<uint8_t>, float, float> *get_packet_trigger() { return &this->packet_trigger_; }
 
  protected:

esphome/components/sx127x/packet_interface/__init__.py

@@ -0,0 +1,68 @@
+from esphome.components import packet_interface
+from esphome.components.packet_interface import CONF_MAX_PACKET_SIZE
+from esphome.components.packet_interface.radio_link import (
+    new_radio_link,
+    radio_link_final_validate,
+    radio_link_schema,
+)
+import esphome.config_validation as cv
+from esphome.types import ConfigType
+
+from .. import (
+    CONF_MODULATION,
+    CONF_PACKET_MODE,
+    CONF_PAYLOAD_LENGTH,
+    CONF_RX_START,
+    CONF_SX127X_ID,
+    CONF_SYNC_VALUE,
+    DOMAIN,
+    SX127x,
+    SX127xListener,
+    sx127x_ns,
+)
+
+CODEOWNERS = ["@clydebarrow"]
+DEPENDENCIES = ["sx127x"]
+
+# The FIFO limit outside LoRa mode
+FSK_MAX_PACKET_SIZE = 64
+
+SX127xPacketInterface = sx127x_ns.class_(
+    "SX127xPacketInterface", packet_interface.PacketInterface, SX127xListener
+)
+
+CONFIG_SCHEMA = radio_link_schema(SX127xPacketInterface, CONF_SX127X_ID, SX127x)
+
+
+def _check_fsk(config: ConfigType, radio: ConfigType) -> None:
+    """Without LoRa, the radio must send packets, not a continuous bit stream, and holds fewer bytes.
+
+    It can tell that a packet is arriving only from its sync word, which listen before talk needs.
+    """
+    if radio[CONF_MODULATION] == "LORA":
+        return
+    if not radio.get(CONF_PACKET_MODE, False):
+        raise cv.Invalid(
+            f"Without LoRa modulation the radio's '{CONF_PACKET_MODE}' must be true, as a link sends packets",
+            path=[CONF_SX127X_ID],
+        )
+    if not radio.get(CONF_SYNC_VALUE):
+        raise cv.Invalid(
+            f"Without LoRa modulation the radio needs a '{CONF_SYNC_VALUE}', so that the link can tell when a "
+            "packet is arriving and not send over it",
+            path=[CONF_SX127X_ID],
+        )
+    if config[CONF_MAX_PACKET_SIZE] > FSK_MAX_PACKET_SIZE:
+        raise cv.Invalid(
+            f"Without LoRa modulation the radio sends at most {FSK_MAX_PACKET_SIZE} bytes",
+            path=[CONF_MAX_PACKET_SIZE],
+        )
+
+
+FINAL_VALIDATE_SCHEMA = radio_link_final_validate(
+    CONF_SX127X_ID, CONF_PAYLOAD_LENGTH, CONF_RX_START, _check_fsk
+)
+
+
+async def to_code(config: ConfigType) -> None:
+    await new_radio_link(config, CONF_SX127X_ID, DOMAIN)

esphome/components/sx127x/packet_interface/sx127x_packet_interface.h

@@ -0,0 +1,10 @@
+#pragma once
+
+#include "esphome/components/packet_interface/radio_link.h"
+#include "esphome/components/sx127x/sx127x.h"
+
+namespace esphome::sx127x {
+
+using SX127xPacketInterface = packet_interface::RadioLink<SX127x, SX127xListener, SX127xError, SX127X_MAX_PACKET_SIZE>;
+
+}  // namespace esphome::sx127x

esphome/components/sx127x/sx127x.cpp

@@ -354,6 +354,18 @@ void SX127x::loop() {
   }
 }
 
+bool SX127x::is_receiving() {
+  // In receive mode DIO0 signals a received packet; the transmit FIFO would overwrite it
+  if (this->dio0_pin_ != nullptr && this->dio0_pin_->digital_read())
+    return true;
+  if (this->modulation_ != MOD_LORA) {
+    // Set from the sync word until the packet has been read; the preamble flag stays set when no sync word follows
+    return (this->read_register_(REG_IRQ_FLAGS_1) & IRQ_FLAGS_1_SYNC_ADDRESS_MATCH) != 0;
+  }
+  return (this->read_register_(REG_MODEM_STAT) &
+          (MODEM_STAT_SIGNAL_DETECTED | MODEM_STAT_SIGNAL_SYNCHRONIZED | MODEM_STAT_HEADER_VALID)) != 0;
+}
+
 void SX127x::run_image_cal() {
   if (this->modulation_ == MOD_LORA) {
     this->set_mode_(MOD_FSK, MODE_SLEEP);

esphome/components/sx127x/sx127x.h

@@ -88,6 +88,8 @@ class SX127x final : public Component,
     return this->transmit_packet(packet.data(), packet.size());
   }
   void register_listener(SX127xListener *listener) { this->listeners_.push_back(listener); }
+  /// True while a packet is being received, or has been received and not yet read; sending would lose it.
+  bool is_receiving();
   Trigger<std::vector<uint8_t>, float, float> *get_packet_trigger() { return &this->packet_trigger_; }
 
  protected: