Apply the periodic frame minimum to engineering frames too

esphome/components/ld2412/ld2412.cpp

@@ -186,23 +186,19 @@ static constexpr uint8_t CMD_DURATION_VALUE = 0x02;
 // Bitmasks for target states
 static constexpr uint8_t MOVE_BITMASK = 0x01;
 static constexpr uint8_t STILL_BITMASK = 0x02;
-// Header & Footer size
-static constexpr uint8_t HEADER_FOOTER_SIZE = 4;
-// Command Header & Footer
-static constexpr uint8_t CMD_FRAME_HEADER[HEADER_FOOTER_SIZE] = {0xFD, 0xFC, 0xFB, 0xFA};
-static constexpr uint8_t CMD_FRAME_FOOTER[HEADER_FOOTER_SIZE] = {0x04, 0x03, 0x02, 0x01};
+using ld24xx::CMD_FRAME_FOOTER;
+using ld24xx::CMD_FRAME_HEADER;
+using ld24xx::HEADER_FOOTER_SIZE;
+using ld24xx::validate_header_footer;
+// Smallest frames whose values can all be read: the last value, data footer and check, then the frame footer
+static constexpr uint8_t PERIODIC_FRAME_MIN = STILL_ENERGY + 3 + HEADER_FOOTER_SIZE;
+static constexpr uint8_t ENGINEERING_FRAME_MIN = LIGHT_SENSOR + 3 + HEADER_FOOTER_SIZE;
 // Data Header & Footer
 static constexpr uint8_t DATA_FRAME_HEADER[HEADER_FOOTER_SIZE] = {0xF4, 0xF3, 0xF2, 0xF1};
 static constexpr uint8_t DATA_FRAME_FOOTER[HEADER_FOOTER_SIZE] = {0xF8, 0xF7, 0xF6, 0xF5};
 // MAC address the module uses when Bluetooth is disabled
 static constexpr uint8_t NO_MAC[] = {0x08, 0x05, 0x04, 0x03, 0x02, 0x01};
 static constexpr uint8_t GATE_SENS_ACK_SIZE = ACK_PAYLOAD + TOTAL_GATES + HEADER_FOOTER_SIZE;
-// The length field counts the command word, the status word and the gates
-static constexpr uint16_t GATE_SENS_ACK_LENGTH = GATE_SENS_ACK_SIZE - COMMAND - HEADER_FOOTER_SIZE;
-
-static inline bool validate_header_footer(const uint8_t *header_footer, const uint8_t *buffer) {
-  return std::memcmp(header_footer, buffer, HEADER_FOOTER_SIZE) == 0;
-}
 
 void LD2412Component::dump_config() {
   char mac_s[MAC_ADDRESS_PRETTY_BUFFER_SIZE];
@@ -371,6 +367,9 @@ void LD2412Component::handle_periodic_data_() {
     0x02: Normal mode
   */
   bool engineering_mode = this->buffer_data_[DATA_TYPES] == 0x01;
+  if (this->buffer_pos_ < PERIODIC_FRAME_MIN) {
+    return;  // too short to hold the values
+  }
 #ifdef USE_SWITCH
   if (this->engineering_mode_switch_ != nullptr) {
     this->engineering_mode_switch_->publish_state(engineering_mode);
@@ -421,8 +420,7 @@ void LD2412Component::handle_periodic_data_() {
     this->detection_distance_sensor_.publish_state_if_not_dup(new_detect_distance);
   }
   if (engineering_mode) {
-    // Engineering mode needs at least LIGHT_SENSOR + 1 bytes
-    if (this->buffer_pos_ < LIGHT_SENSOR + 1) {
+    if (this->buffer_pos_ < ENGINEERING_FRAME_MIN) {
       ESP_LOGW(TAG, "Engineering mode packet too short: %u", this->buffer_pos_);
     } else {
       /*
@@ -477,24 +475,15 @@ static constexpr uint32_t GATE_QUERY_TIMEOUT_ID = 0;
 static constexpr uint32_t GATE_QUERY_TIMEOUT_MS = 2000;
 #endif
 
-bool LD2412Component::handle_ack_data_() {
+void LD2412Component::handle_ack_data_() {
   ESP_LOGV(TAG, "Handling ACK DATA for COMMAND %02X", this->buffer_data_[COMMAND]);
-  if (this->buffer_pos_ < 10) {
-    ESP_LOGW(TAG, "Invalid length");
-    return true;
-  }
-  if (!ld2412::validate_header_footer(CMD_FRAME_HEADER, this->buffer_data_)) {
-    char hex_buf[format_hex_pretty_size(HEADER_FOOTER_SIZE)];
-    ESP_LOGW(TAG, "Invalid header: %s", format_hex_pretty_to(hex_buf, this->buffer_data_, HEADER_FOOTER_SIZE));
-    return true;
-  }
   if (this->buffer_data_[COMMAND_STATUS] != 0x01) {
     ESP_LOGW(TAG, "Invalid status");
-    return true;
+    return;
   }
   if (this->buffer_data_[8] || this->buffer_data_[9]) {
     ESP_LOGW(TAG, "Invalid command: %02X, %02X", this->buffer_data_[8], this->buffer_data_[9]);
-    return true;
+    return;
   }
 
   switch (this->buffer_data_[COMMAND]) {
@@ -517,8 +506,8 @@ bool LD2412Component::handle_ack_data_() {
       break;
 
     case CMD_QUERY_VERSION: {
-      if (this->buffer_pos_ < 12 + sizeof(this->version_)) {
-        return false;
+      if (this->buffer_pos_ < 12 + sizeof(this->version_) + HEADER_FOOTER_SIZE) {
+        break;  // too short to hold a version
       }
       std::memcpy(this->version_, &this->buffer_data_[12], sizeof(this->version_));
       char version_s[20];
@@ -532,6 +521,9 @@ bool LD2412Component::handle_ack_data_() {
       break;
     }
     case CMD_QUERY_DISTANCE_RESOLUTION: {
+      if (this->buffer_pos_ < 11 + HEADER_FOOTER_SIZE) {
+        break;  // too short to hold the resolution
+      }
       const auto *distance_resolution = find_str(DISTANCE_RESOLUTIONS_BY_UINT, this->buffer_data_[10]);
       ESP_LOGV(TAG, "Distance resolution: %s", distance_resolution);
 #ifdef USE_SELECT
@@ -543,6 +535,9 @@ bool LD2412Component::handle_ack_data_() {
     }
 
     case CMD_QUERY_LIGHT_CONTROL: {
+      if (this->buffer_pos_ < 12 + HEADER_FOOTER_SIZE) {
+        break;  // too short to hold the light settings
+      }
       this->light_function_ = this->buffer_data_[10];
       this->light_threshold_ = this->buffer_data_[11];
       const auto *light_function_str = find_str(LIGHT_FUNCTIONS_BY_UINT, this->light_function_);
@@ -562,7 +557,7 @@ bool LD2412Component::handle_ack_data_() {
 
     case CMD_QUERY_MAC_ADDRESS: {
       if (this->buffer_pos_ < 20) {
-        return false;
+        break;  // too short to hold a MAC address
       }
 
       this->bluetooth_on_ = std::memcmp(&this->buffer_data_[10], NO_MAC, sizeof(NO_MAC)) != 0;
@@ -591,6 +586,9 @@ bool LD2412Component::handle_ack_data_() {
       break;
 
     case CMD_QUERY_DYNAMIC_BACKGROUND_CORRECTION: {
+      if (this->buffer_pos_ < 11 + HEADER_FOOTER_SIZE) {
+        break;  // too short to hold the state
+      }
       ESP_LOGV(TAG, "Handled query dynamic background correction");
       bool dynamic_background_correction_active = (this->buffer_data_[10] != 0x00);
 #ifdef USE_BINARY_SENSOR
@@ -613,14 +611,10 @@ bool LD2412Component::handle_ack_data_() {
     case CMD_QUERY_MOTION_GATE_SENS:
     case CMD_QUERY_STATIC_GATE_SENS: {
 #ifdef USE_NUMBER
-      const uint16_t declared = encode_uint16(this->buffer_data_[FRAME_LENGTH + 1], this->buffer_data_[FRAME_LENGTH]);
-      if (declared != GATE_SENS_ACK_LENGTH || this->buffer_pos_ > GATE_SENS_ACK_SIZE) {
-        // A truncated answer merged with the next frame, or a length this driver does not know
+      if (this->buffer_pos_ != GATE_SENS_ACK_SIZE) {
+        // A length this driver does not know
         ESP_LOGW(TAG, "Dropping gate threshold answer of %u bytes", this->buffer_pos_);
-        return true;
-      }
-      if (this->buffer_pos_ < GATE_SENS_ACK_SIZE) {
-        return false;  // the footer pattern appeared inside the payload, keep reading
+        return;
       }
       const bool motion = this->buffer_data_[COMMAND] == CMD_QUERY_MOTION_GATE_SENS;
       GateThresholds &group = this->gate_thresholds_(motion);
@@ -646,8 +640,8 @@ bool LD2412Component::handle_ack_data_() {
     case CMD_QUERY_BASIC_CONF:  // Query parameters response
     {
 #ifdef USE_NUMBER
-      if (this->buffer_pos_ < 15) {
-        return false;
+      if (this->buffer_pos_ < 15 + HEADER_FOOTER_SIZE) {
+        break;  // too short to hold the configuration
       }
       /*
         Moving distance range: 9th byte
@@ -677,42 +671,36 @@ bool LD2412Component::handle_ack_data_() {
     default:
       break;
   }
-
-  return true;
 }
 
 void LD2412Component::readline_(int readch) {
   if (readch < 0) {
     return;  // No data available
   }
-  if (this->buffer_pos_ < HEADER_FOOTER_SIZE && readch != DATA_FRAME_HEADER[this->buffer_pos_] &&
-      readch != CMD_FRAME_HEADER[this->buffer_pos_]) {
-    this->buffer_pos_ = 0;
-    return;
-  }
-  if (this->buffer_pos_ < MAX_LINE_LENGTH - 1) {
-    this->buffer_data_[this->buffer_pos_++] = readch;
-    this->buffer_data_[this->buffer_pos_] = 0;
-  } else {
-    // We should never get here, but just in case...
-    ESP_LOGW(TAG, "Max command length exceeded; ignoring");
-    this->buffer_pos_ = 0;
-  }
-  if (this->buffer_pos_ < 4) {
-    return;  // Not enough data to process yet
-  }
-  if (ld2412::validate_header_footer(DATA_FRAME_FOOTER, &this->buffer_data_[this->buffer_pos_ - 4])) {
+  // Periodic and command frames both carry their count after the header
+  ld24xx::feed_frame_byte(
+      this->buffer_data_, this->buffer_pos_, readch, DATA_FRAME_HEADER, ld24xx::cmd_frame_length,
+      [this](uint8_t frame_len) { return this->handle_frame_(frame_len); }, []() { ESP_LOGW(TAG, "Invalid length"); });
+}
+
+// Dispatches the frame of frame_len bytes at the start of the buffer when its footer is in place
+bool LD2412Component::handle_frame_(uint8_t frame_len) {
+  this->buffer_pos_ = frame_len;  // the handlers take the frame length from here
+  const uint8_t *tail = &this->buffer_data_[frame_len - HEADER_FOOTER_SIZE];
+  if (this->buffer_data_[0] == DATA_FRAME_HEADER[0]) {
+    if (!ld2412::validate_header_footer(DATA_FRAME_FOOTER, tail)) {
+      return false;
+    }
     ESP_LOGV_HEX(TAG, this->buffer_data_, this->buffer_pos_, MAX_LINE_LENGTH, "Handling Periodic Data: %s");
     this->handle_periodic_data_();
-    this->buffer_pos_ = 0;  // Reset position index for next message
-  } else if (ld2412::validate_header_footer(CMD_FRAME_FOOTER, &this->buffer_data_[this->buffer_pos_ - 4])) {
-    ESP_LOGV_HEX(TAG, this->buffer_data_, this->buffer_pos_, MAX_LINE_LENGTH, "Handling Ack Data: %s");
-    if (this->handle_ack_data_()) {
-      this->buffer_pos_ = 0;  // Reset position index for next message
-    } else {
-      ESP_LOGV(TAG, "Ack Data incomplete");
-    }
+    return true;
   }
+  if (!ld2412::validate_header_footer(CMD_FRAME_FOOTER, tail)) {
+    return false;
+  }
+  ESP_LOGV_HEX(TAG, this->buffer_data_, this->buffer_pos_, MAX_LINE_LENGTH, "Handling Ack Data: %s");
+  this->handle_ack_data_();
+  return true;
 }
 
 void LD2412Component::set_config_mode_(bool enable) {

esphome/components/ld2412/ld2412.h

@@ -111,7 +111,8 @@ class LD2412Component final : public Component, public uart::UARTDevice {
   void send_command_(uint8_t command_str, const uint8_t *command_value, uint8_t command_value_len);
   void set_config_mode_(bool enable);
   void handle_periodic_data_();
-  bool handle_ack_data_();
+  void handle_ack_data_();
+  bool handle_frame_(uint8_t frame_len);
   void readline_(int readch);
   void query_parameters_();
   void get_version_();

esphome/components/ld24xx/ld24xx.h

@@ -3,6 +3,8 @@
 #include "esphome/core/defines.h"
 #include "esphome/core/helpers.h"
 
+#include <algorithm>
+#include <cstring>
 #include <memory>
 #include <span>
 
@@ -53,6 +55,74 @@ inline void format_version_str(const uint8_t *version, std::span<char, 20> buffe
            version[2]);
 }
 
+// Commands and their answers share this header, a little-endian byte count and this footer
+static constexpr uint8_t HEADER_FOOTER_SIZE = 4;
+static constexpr uint8_t CMD_FRAME_HEADER[HEADER_FOOTER_SIZE] = {0xFD, 0xFC, 0xFB, 0xFA};
+static constexpr uint8_t CMD_FRAME_FOOTER[HEADER_FOOTER_SIZE] = {0x04, 0x03, 0x02, 0x01};
+
+inline bool validate_header_footer(const uint8_t *header_footer, const uint8_t *buffer) {
+  return std::memcmp(header_footer, buffer, HEADER_FOOTER_SIZE) == 0;
+}
+
+// Whole command frame length, or 0 until the count arrives; 32 bit so 0xFFFF cannot wrap to 0
+inline uint32_t cmd_frame_length(const uint8_t *buffer, uint8_t count) {
+  if (count < HEADER_FOOTER_SIZE + 2) {
+    return 0;
+  }
+  return HEADER_FOOTER_SIZE + 2 + encode_value_le<uint16_t>(&buffer[HEADER_FOOTER_SIZE]) + HEADER_FOOTER_SIZE;
+}
+
+// Drops the first `from` bytes and anything after them that does not begin a header; returns the bytes kept
+inline uint8_t drop_to_next_header(uint8_t *buffer, uint8_t count, uint8_t from, const uint8_t *data_header) {
+  for (; from < count; from++) {
+    const size_t n = std::min<size_t>(HEADER_FOOTER_SIZE, count - from);
+    if (std::memcmp(&buffer[from], CMD_FRAME_HEADER, n) == 0 || std::memcmp(&buffer[from], data_header, n) == 0) {
+      std::memmove(buffer, &buffer[from], count - from);
+      return count - from;
+    }
+  }
+  return 0;
+}
+
+// Feeds one byte into a frame buffer. A frame opens with the command header or `data_header` and ends at
+// `frame_length(buffer, count)` bytes (0 while unknown); `handle_frame(len)` returns false for a footer out
+// of place. A dropped or oversized frame calls `on_drop()`. The handler may overwrite `pos`; the splitter
+// works from the count it saved.
+template<size_t N, typename LengthFn, typename HandleFn, typename DropFn>
+void feed_frame_byte(uint8_t (&buffer)[N], uint8_t &pos, uint8_t byte, const uint8_t *data_header,
+                     LengthFn frame_length, HandleFn handle_frame, DropFn on_drop) {
+  // The first byte picks the header; bytes that do not continue it are dropped
+  if (pos > 0 && pos < HEADER_FOOTER_SIZE) {
+    const uint8_t *header = buffer[0] == data_header[0] ? data_header : CMD_FRAME_HEADER;
+    if (byte != header[pos]) {
+      pos = 0;
+    }
+  }
+  if (pos == 0 && byte != data_header[0] && byte != CMD_FRAME_HEADER[0]) {
+    return;
+  }
+  buffer[pos++] = byte;
+  // Drain every whole frame left in the buffer
+  while (true) {
+    const uint32_t frame_len = frame_length(buffer, pos);
+    if (frame_len == 0 || (frame_len <= N && pos < frame_len)) {
+      return;
+    }
+    const uint8_t total = pos;
+    // Keep only what begins a header: after the frame, or after its first byte when it is dropped
+    uint8_t from = 1;
+    if (frame_len <= N && handle_frame(static_cast<uint8_t>(frame_len))) {
+      from = frame_len;
+    } else {
+      on_drop();
+    }
+    pos = drop_to_next_header(buffer, total, from, data_header);
+    if (pos == 0) {
+      return;
+    }
+  }
+}
+
 #ifdef USE_SENSOR
 template<typename T> using SensorWithDedup = sensor::SensorWithDedup<T>;
 #endif

tests/components/ld24xx/ld24xx_frame_splitter.cpp

@@ -0,0 +1,152 @@
+#include <cstdint>
+#include <cstring>
+#include <vector>
+#include <gtest/gtest.h>
+#include "esphome/components/ld24xx/ld24xx.h"
+
+namespace esphome::ld24xx::testing {
+
+namespace {
+constexpr uint8_t DATA_FRAME_HEADER[HEADER_FOOTER_SIZE] = {0xF4, 0xF3, 0xF2, 0xF1};
+constexpr uint8_t DATA_FRAME_FOOTER[HEADER_FOOTER_SIZE] = {0xF8, 0xF7, 0xF6, 0xF5};
+constexpr uint8_t DATA_FRAME_SIZE = 12;  // header, four payload bytes, footer
+constexpr size_t BUFFER_SIZE = 40;
+
+// Command frame around the payload
+std::vector<uint8_t> make_cmd_frame(const std::vector<uint8_t> &payload) {
+  std::vector<uint8_t> frame(std::begin(CMD_FRAME_HEADER), std::end(CMD_FRAME_HEADER));
+  frame.push_back(payload.size());
+  frame.push_back(0x00);
+  frame.insert(frame.end(), payload.begin(), payload.end());
+  frame.insert(frame.end(), std::begin(CMD_FRAME_FOOTER), std::end(CMD_FRAME_FOOTER));
+  return frame;
+}
+
+std::vector<uint8_t> make_data_frame(uint8_t fill) {
+  std::vector<uint8_t> frame(std::begin(DATA_FRAME_HEADER), std::end(DATA_FRAME_HEADER));
+  frame.insert(frame.end(), DATA_FRAME_SIZE - 2 * HEADER_FOOTER_SIZE, fill);
+  frame.insert(frame.end(), std::begin(DATA_FRAME_FOOTER), std::end(DATA_FRAME_FOOTER));
+  return frame;
+}
+}  // namespace
+
+// Data frames are fixed size, command frames carry their count, as in the radar components
+class LD24xxFrameSplitterTest : public ::testing::Test {
+ protected:
+  void feed_(const std::vector<uint8_t> &bytes) {
+    for (uint8_t byte : bytes) {
+      feed_frame_byte(
+          this->buffer_, this->pos_, byte, DATA_FRAME_HEADER,
+          [](const uint8_t *buffer, uint8_t count) -> uint32_t {
+            if (count < HEADER_FOOTER_SIZE) {
+              return 0;
+            }
+            return buffer[0] == DATA_FRAME_HEADER[0] ? DATA_FRAME_SIZE : cmd_frame_length(buffer, count);
+          },
+          [this](uint8_t frame_len) { return this->handle_frame_(frame_len); }, [this]() { this->drops_++; });
+    }
+  }
+
+  bool handle_frame_(uint8_t frame_len) {
+    const uint8_t *footer = this->buffer_[0] == DATA_FRAME_HEADER[0] ? DATA_FRAME_FOOTER : CMD_FRAME_FOOTER;
+    if (!validate_header_footer(footer, &this->buffer_[frame_len - HEADER_FOOTER_SIZE])) {
+      return false;
+    }
+    this->frames_.emplace_back(this->buffer_, this->buffer_ + frame_len);
+    return true;
+  }
+
+  uint8_t buffer_[BUFFER_SIZE];
+  uint8_t pos_{0};
+  std::vector<std::vector<uint8_t>> frames_;
+  int drops_{0};
+};
+
+TEST_F(LD24xxFrameSplitterTest, FooterBytesInThePayloadDoNotEndTheFrame) {
+  auto frame = make_cmd_frame({0x61, 0x01, 0x00, 0x00, 0x04, 0x03, 0x02, 0x01, 0x55});
+  this->feed_(frame);
+  ASSERT_EQ(this->frames_.size(), 1u);
+  EXPECT_EQ(this->frames_[0], frame);
+  EXPECT_EQ(this->pos_, 0);
+  EXPECT_EQ(this->drops_, 0);
+}
+
+TEST_F(LD24xxFrameSplitterTest, BytesBeforeAHeaderAreNeverBuffered) {
+  this->feed_({0x00, 0x11, 0xFC, 0xFB, 0xFA, 0x04});
+  EXPECT_EQ(this->pos_, 0);
+  this->feed_(make_data_frame(0x22));
+  ASSERT_EQ(this->frames_.size(), 1u);
+  EXPECT_EQ(this->frames_[0], make_data_frame(0x22));
+}
+
+TEST_F(LD24xxFrameSplitterTest, AHeaderRestartsWhenItsBytesStopMatching) {
+  // F3 cannot continue the command header, and FD after FC starts it over
+  this->feed_({0xFD, 0xF3, 0xFD, 0xFC, 0xFD, 0xFC, 0xFB, 0xFA, 0x00, 0x00});
+  EXPECT_EQ(this->pos_, 6) << "only the header that matched through and its count are buffered";
+  this->feed_({0x04, 0x03, 0x02, 0x01});
+  ASSERT_EQ(this->frames_.size(), 1u);
+  EXPECT_EQ(this->frames_[0], make_cmd_frame({}));
+  EXPECT_EQ(this->drops_, 0);
+}
+
+TEST_F(LD24xxFrameSplitterTest, ImpossibleCountsAreDroppedAndTheNextFrameParsed) {
+  // 0xFFF6 totals 65536, which must not wrap to 0
+  this->feed_({0xFD, 0xFC, 0xFB, 0xFA, 0xF6, 0xFF});
+  this->feed_({0xFD, 0xFC, 0xFB, 0xFA, 0xFF, 0xFF});
+  EXPECT_EQ(this->drops_, 2);
+  EXPECT_EQ(this->pos_, 0);
+  this->feed_(make_data_frame(0x33));
+  ASSERT_EQ(this->frames_.size(), 1u);
+  EXPECT_EQ(this->frames_[0], make_data_frame(0x33));
+}
+
+TEST_F(LD24xxFrameSplitterTest, AFrameCaughtInsideADroppedFrameIsReplayed) {
+  // The count reaches 20 bytes in, past the whole frame that follows
+  std::vector<uint8_t> bytes = {0xFD, 0xFC, 0xFB, 0xFA, 0x0A, 0x00, 0x61, 0x01};
+  auto inner = make_data_frame(0x44);
+  bytes.insert(bytes.end(), inner.begin(), inner.end());
+  this->feed_(bytes);
+  EXPECT_EQ(this->drops_, 1);
+  ASSERT_EQ(this->frames_.size(), 1u);
+  EXPECT_EQ(this->frames_[0], inner);
+  EXPECT_EQ(this->pos_, 0);
+}
+
+TEST_F(LD24xxFrameSplitterTest, EveryWholeFrameLeftByADropIsDrained) {
+  // The window holds two whole data frames and the start of a third
+  std::vector<uint8_t> bytes = {0xFD, 0xFC, 0xFB, 0xFA, 0x18, 0x00, 0x61, 0x01};
+  for (uint8_t fill : {0x55, 0x66}) {
+    auto inner = make_data_frame(fill);
+    bytes.insert(bytes.end(), inner.begin(), inner.end());
+  }
+  bytes.insert(bytes.end(), {0xF4, 0xF3});
+  this->feed_(bytes);
+  EXPECT_EQ(this->drops_, 1);
+  ASSERT_EQ(this->frames_.size(), 2u);
+  EXPECT_EQ(this->frames_[0], make_data_frame(0x55));
+  EXPECT_EQ(this->frames_[1], make_data_frame(0x66));
+  EXPECT_EQ(this->pos_, 2) << "the partial header at the end stays buffered";
+}
+
+TEST_F(LD24xxFrameSplitterTest, AWrongFooterDropsOnlyThatFrame) {
+  auto bad = make_cmd_frame({0x01, 0x02});
+  bad[bad.size() - 1] = 0xEE;
+  this->feed_(bad);
+  EXPECT_EQ(this->drops_, 1);
+  EXPECT_TRUE(this->frames_.empty());
+  this->feed_(make_cmd_frame({0x03}));
+  ASSERT_EQ(this->frames_.size(), 1u);
+  EXPECT_EQ(this->frames_[0], make_cmd_frame({0x03}));
+}
+
+TEST_F(LD24xxFrameSplitterTest, BackToBackFramesOfBothKinds) {
+  this->feed_(make_data_frame(0x01));
+  this->feed_(make_cmd_frame({0xA0, 0x01, 0x00, 0x00}));
+  this->feed_(make_data_frame(0x02));
+  ASSERT_EQ(this->frames_.size(), 3u);
+  EXPECT_EQ(this->frames_[1], make_cmd_frame({0xA0, 0x01, 0x00, 0x00}));
+  EXPECT_EQ(this->frames_[2], make_data_frame(0x02));
+  EXPECT_EQ(this->drops_, 0);
+}
+
+}  // namespace esphome::ld24xx::testing

tests/integration/fixtures/uart_mock_ld2412.yaml

@@ -30,7 +30,7 @@ uart_mock:
     # Target state: 0x03 (moving + still)
     # detection_distance = 100 (LD2412 computes from moving target when MOVE_BITMASK set)
     #
-    # Frame layout (24 bytes):
+    # Frame layout (23 bytes):
     #   [0-3]   F4 F3 F2 F1 = data frame header
     #   [4-5]   0D 00       = length 13
     #   [6]     02          = data type (normal)
@@ -41,10 +41,9 @@ uart_mock:
     #   [12-13] 78 00       = still distance 120 (0x0078)
     #   [14]    19          = still energy 25
     #   [15-16] 64 00       = detect distance bytes (ignored by LD2412 code)
-    #   [17]    00          = padding
-    #   [18]    55          = data footer marker
-    #   [19]    00          = CRC/check
-    #   [20-23] F8 F7 F6 F5 = data frame footer
+    #   [17]    55          = data footer marker
+    #   [18]    00          = CRC/check
+    #   [19-22] F8 F7 F6 F5 = data frame footer
     - delay: 100ms
       inject_rx:
         [
@@ -57,7 +56,6 @@ uart_mock:
           0x78, 0x00,
           0x19,
           0x64, 0x00,
-          0x00,
           0x55, 0x00,
           0xF8, 0xF7, 0xF6, 0xF5,
         ]
@@ -69,17 +67,13 @@ uart_mock:
       inject_rx: [0xDE, 0xAD, 0xBE, 0xEF, 0x00, 0x11, 0x22]
 
     # Phase 3 (t=400ms): Truncated frame (header + partial data, no footer)
-    # Starts with valid data frame header so parser accepts it.
-    # After this, buffer_pos_ = 8.
+    # Starts with a valid data frame header, so the parser waits for the 23 bytes its length announces.
     - delay: 100ms
       inject_rx: [0xF4, 0xF3, 0xF2, 0xF1, 0x0D, 0x00, 0x02, 0xAA]
 
-    # Phase 4 (t=600ms): Overflow - inject 60 bytes of 0xFF (MAX_LINE_LENGTH=54)
-    # Buffer has 8 bytes from phase 3 (garbage in phase 2 was rejected).
-    # Overflow math: buffer_pos_ starts at 8, overflow triggers when
-    # buffer_pos_ reaches 53 (MAX_LINE_LENGTH - 1). Need 45 more bytes to
-    # fill positions 8-52, then byte 46 triggers overflow. After overflow,
-    # buffer_pos_ = 0 and remaining 0xFF bytes are rejected (don't match header).
+    # Phase 4 (t=600ms): 60 bytes of 0xFF
+    # The first 15 complete the truncated frame's 23 bytes without its footer, so it is dropped
+    # with an 'Invalid length' warning; the rest cannot start a header and are dropped too.
     - delay: 200ms
       inject_rx:
         [
@@ -91,8 +85,8 @@ uart_mock:
           0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
         ]
 
-    # Phase 5 (t=700ms): Valid frame after overflow - recovery test
-    # Buffer was reset by overflow. This valid frame should parse correctly.
+    # Phase 5 (t=700ms): Valid frame after the garbage - recovery test
+    # The buffer is empty again, so this valid frame should parse correctly.
     # Moving target: 50cm, energy 100
     # Still target: 75cm, energy 80
     # detection_distance = 50 (moving target distance, since MOVE_BITMASK set)
@@ -108,7 +102,72 @@ uart_mock:
           0x4B, 0x00,
           0x50,
           0x32, 0x00,
-          0x00,
+          0x55, 0x00,
+          0xF8, 0xF7, 0xF6, 0xF5,
+        ]
+
+    # Phase 6 (t=3200ms): Values that spell the command footer 04 03 02 01
+    # Moving distance 772 (0x0304), moving energy 2, still distance 1: bytes 9 to 12 are the
+    # command frame footer, which must not end the frame early.
+    # Still energy 5, detection_distance = 772 (moving target distance, since MOVE_BITMASK set).
+    # The sensors hold and throttle values for a second, so the gap lets the phase 5 states
+    # reach the test before these replace them.
+    - delay: 2500ms
+      inject_rx:
+        [
+          0xF4, 0xF3, 0xF2, 0xF1,
+          0x0D, 0x00,
+          0x02, 0xAA,
+          0x03,
+          0x04, 0x03,
+          0x02,
+          0x01, 0x00,
+          0x05,
+          0x04, 0x03,
+          0x55, 0x00,
+          0xF8, 0xF7, 0xF6, 0xF5,
+        ]
+
+    # Phase 7 (t=5700ms): Truncated frame merged with a complete one
+    # The eight header bytes announce a 23 byte frame, so its window takes in the first 15 bytes of
+    # the valid frame that follows. The merged frame has no footer where the count says, so it is
+    # dropped and the bytes after its header are replayed, which recovers the valid frame.
+    # Moving distance 400, moving energy 7, still distance 200, still energy 9, detection_distance = 400
+    - delay: 2500ms
+      inject_rx:
+        [
+          0xF4, 0xF3, 0xF2, 0xF1, 0x0D, 0x00, 0x02, 0xAA,
+          0xF4, 0xF3, 0xF2, 0xF1,
+          0x0D, 0x00,
+          0x02, 0xAA,
+          0x03,
+          0x90, 0x01,
+          0x07,
+          0xC8, 0x00,
+          0x09,
+          0x90, 0x01,
+          0x55, 0x00,
+          0xF8, 0xF7, 0xF6, 0xF5,
+        ]
+
+    # Phase 8 (t=8200ms): Impossible counts, then a complete frame
+    # A command header counting 0xFFF6 bytes (65536 in total, which must not wrap to 0) and one counting
+    # 0xFFFF are each dropped as soon as the count arrives, and the valid frame after them is parsed.
+    # Moving distance 600, moving energy 11, still distance 300, still energy 13, detection distance 600
+    - delay: 2500ms
+      inject_rx:
+        [
+          0xFD, 0xFC, 0xFB, 0xFA, 0xF6, 0xFF,
+          0xFD, 0xFC, 0xFB, 0xFA, 0xFF, 0xFF,
+          0xF4, 0xF3, 0xF2, 0xF1,
+          0x0D, 0x00,
+          0x02, 0xAA,
+          0x03,
+          0x58, 0x02,
+          0x0B,
+          0x2C, 0x01,
+          0x0D,
+          0x58, 0x02,
           0x55, 0x00,
           0xF8, 0xF7, 0xF6, 0xF5,
         ]

tests/integration/fixtures/uart_mock_ld2412_short_answers.yaml

@@ -0,0 +1,88 @@
+esphome:
+  name: uart-mock-ld2412-short-answers
+
+host:
+api:
+  batch_delay: 0ms  # Disable batching to receive all state updates
+logger:
+  level: VERBOSE
+
+external_components:
+  - source:
+      type: local
+      path: EXTERNAL_COMPONENT_PATH
+
+# Dummy uart entry to satisfy ld2412's DEPENDENCIES = ["uart"]
+# The actual UART bus used is the uart_mock component below
+uart:
+  baud_rate: 115200
+  port: /dev/null
+
+# Answers cut short, so the footer sits where their values would be, each followed by a whole one
+uart_mock:
+  id: mock_uart
+  baud_rate: 256000
+  auto_start: false
+  injections:
+    # Version answer cut after two version bytes
+    - delay: 100ms
+      inject_rx:
+        [
+          0xFD, 0xFC, 0xFB, 0xFA, 0x08, 0x00, 0xA0, 0x01, 0x00, 0x00,
+          0x00, 0x01, 0x07, 0x02,
+          0x04, 0x03, 0x02, 0x01,
+        ]
+
+    # Basic configuration answer cut after the minimum gate 7
+    - delay: 100ms
+      inject_rx:
+        [
+          0xFD, 0xFC, 0xFB, 0xFA, 0x05, 0x00, 0x12, 0x01, 0x00, 0x00,
+          0x07,
+          0x04, 0x03, 0x02, 0x01,
+        ]
+
+    # Whole version answer: firmware type 1, version 2.07.22062416
+    - delay: 100ms
+      inject_rx:
+        [
+          0xFD, 0xFC, 0xFB, 0xFA, 0x0C, 0x00, 0xA0, 0x01, 0x00, 0x00,
+          0x00, 0x01, 0x07, 0x02, 0x16, 0x24, 0x06, 0x22,
+          0x04, 0x03, 0x02, 0x01,
+        ]
+
+    # Whole basic configuration answer: gates 3 to 9, timeout 10 s, output pin level low
+    - delay: 100ms
+      inject_rx:
+        [
+          0xFD, 0xFC, 0xFB, 0xFA, 0x09, 0x00, 0x12, 0x01, 0x00, 0x00,
+          0x03, 0x09, 0x0A, 0x00, 0x01,
+          0x04, 0x03, 0x02, 0x01,
+        ]
+
+ld2412:
+  id: ld2412_dev
+  uart_id: mock_uart
+
+number:
+  - platform: ld2412
+    ld2412_id: ld2412_dev
+    min_distance_gate:
+      name: "Min Distance Gate"
+    max_distance_gate:
+      name: "Max Distance Gate"
+    timeout:
+      name: "Timeout"
+
+text_sensor:
+  - platform: ld2412
+    ld2412_id: ld2412_dev
+    version:
+      name: "Version"
+
+button:
+  - platform: template
+    name: "Start Scenario"
+    id: start_scenario_btn
+    on_press:
+      - lambda: 'id(mock_uart).start_scenario();'

tests/integration/fixtures/uart_mock_ld2412_truncated_answer.yaml

@@ -37,7 +37,7 @@ uart_mock:
           0x04, 0x00,  # length 4
           0xFE, 0x01,  # answer to command 0x00FE
           0x00, 0x00,  # status: success
-          0x04, 0x03, 0x02, 0x01,  # its footer; the merged 40-byte frame gets dropped
+          0x04, 0x03, 0x02, 0x01,  # its footer; the 28 bytes the answer announced hold no footer, so it is dropped
         ]
   # A complete answer after setup proves the parser recovered
   injections:

tests/integration/test_uart_mock_ld2412.py

@@ -5,9 +5,12 @@ test_uart_mock_ld2412 (normal mode):
   1. Happy path - valid data frame publishes correct sensor values
   2. Garbage resilience - random bytes don't crash the component
   3. Truncated frame handling - partial frame doesn't corrupt state
-  4. Buffer overflow recovery - overflow resets the parser
-  5. Post-overflow parsing - next valid frame after overflow is parsed correctly
-  6. TX logging - verifies LD2412 sends expected setup commands
+  4. Truncated frame recovery - the frame is dropped once its length is reached
+  5. Post-garbage parsing - the next valid frame is parsed correctly
+  6. Footer bytes in the values - a frame whose values spell the command footer is parsed whole
+  7. Replay after a drop - a valid frame caught inside a dropped frame's window is still parsed
+  8. Impossible counts - a length field of 0xFFF6 or 0xFFFF is dropped and the next frame is parsed
+  9. TX logging - verifies LD2412 sends expected setup commands
 
 test_uart_mock_ld2412_engineering (engineering mode):
   1. Engineering mode frames with per-gate energy data and light sensor
@@ -24,6 +27,7 @@ test_uart_mock_ld2412_engineering_truncated (truncated engineering mode):
 The gate threshold tests (footer_in_payload, truncated_answer, requery_after_giveup) cover
 answers that hold the frame footer or are truncated, writes that fill the gates without a
 number from the module's values, and writes held back until the module reports them.
+test_uart_mock_ld2412_short_answers: answers cut short publish nothing, the whole ones after them do.
 """
 
 from __future__ import annotations
@@ -39,6 +43,7 @@ from aioesphomeapi import (
     EntityState,
     NumberInfo,
     NumberState,
+    TextSensorState,
 )
 import pytest
 
@@ -138,18 +143,18 @@ async def test_uart_mock_ld2412(
     run_compiled: RunCompiledFunction,
     api_client_connected: APIClientConnectedFactory,
 ) -> None:
-    """Test LD2412 data parsing with happy path, garbage, overflow, and recovery."""
+    """Test LD2412 data parsing with happy path, garbage, a truncated frame, and recovery."""
     loop = asyncio.get_running_loop()
 
-    # Track overflow warning in logs
-    overflow_seen = loop.create_future()
+    # Track the warning for the dropped truncated frame in logs
+    resync_seen = loop.create_future()
 
     # Track TX data logged by the mock for assertions
     tx_log_lines: list[str] = []
 
     def line_callback(line: str) -> None:
-        if "Max command length exceeded" in line and not overflow_seen.done():
-            overflow_seen.set_result(True)
+        if "Invalid length" in line and not resync_seen.done():
+            resync_seen.set_result(True)
         # Capture all TX log lines from uart_mock
         if _is_tx(line):
             tx_log_lines.append(line)
@@ -177,6 +182,22 @@ async def test_uart_mock_ld2412(
             and pytest.approx(100.0) in collector.sensor_states["moving_energy"]
             and pytest.approx(80.0) in collector.sensor_states["still_energy"]
             and pytest.approx(50.0) in collector.sensor_states["detection_distance"]
+            and pytest.approx(772.0) in collector.sensor_states["moving_distance"]
+            and pytest.approx(400.0) in collector.sensor_states["moving_distance"]
+            # Every value asserted below, so no state can still be in flight when the waiter fires
+            and pytest.approx(2.0) in collector.sensor_states["moving_energy"]
+            and pytest.approx(1.0) in collector.sensor_states["still_distance"]
+            and pytest.approx(5.0) in collector.sensor_states["still_energy"]
+            and pytest.approx(772.0) in collector.sensor_states["detection_distance"]
+            and pytest.approx(7.0) in collector.sensor_states["moving_energy"]
+            and pytest.approx(200.0) in collector.sensor_states["still_distance"]
+            and pytest.approx(9.0) in collector.sensor_states["still_energy"]
+            and pytest.approx(400.0) in collector.sensor_states["detection_distance"]
+            and pytest.approx(600.0) in collector.sensor_states["moving_distance"]
+            and pytest.approx(11.0) in collector.sensor_states["moving_energy"]
+            and pytest.approx(300.0) in collector.sensor_states["still_distance"]
+            and pytest.approx(13.0) in collector.sensor_states["still_energy"]
+            and pytest.approx(600.0) in collector.sensor_states["detection_distance"]
         )
     )
 
@@ -204,18 +225,16 @@ async def test_uart_mock_ld2412(
         assert collector.sensor_states["detection_distance"][0] == pytest.approx(100.0)
 
         # Wait for the recovery frame (Phase 5) to be parsed
-        # This proves the component survived garbage + truncated + overflow
+        # This proves the component survived garbage + truncated frame + filler bytes
         await wait_or_fail(
             recovery_received,
-            3.0,
+            15.0,
             "Timeout waiting for recovery frame",
             sensor_states=collector.sensor_states,
         )
 
-        # Verify overflow warning was logged
-        assert overflow_seen.done(), (
-            "Expected 'Max command length exceeded' warning in logs"
-        )
+        # Verify the truncated frame was dropped with a warning
+        assert resync_seen.done(), "Expected 'Invalid length' warning in logs"
 
         # Verify LD2412 sent setup commands (TX logging)
         assert len(tx_log_lines) > 0, "Expected TX log lines from uart_mock"
@@ -235,6 +254,27 @@ async def test_uart_mock_ld2412(
         assert pytest.approx(80.0) in collector.sensor_states["still_energy"]
         assert pytest.approx(50.0) in collector.sensor_states["detection_distance"]
 
+        # Phase 6: the values 04 03 02 01 did not end the frame early
+        assert pytest.approx(772.0) in collector.sensor_states["moving_distance"]
+        assert pytest.approx(2.0) in collector.sensor_states["moving_energy"]
+        assert pytest.approx(1.0) in collector.sensor_states["still_distance"]
+        assert pytest.approx(5.0) in collector.sensor_states["still_energy"]
+        assert pytest.approx(772.0) in collector.sensor_states["detection_distance"]
+
+        # Phase 7: the valid frame inside the dropped frame's window was replayed and parsed
+        assert pytest.approx(400.0) in collector.sensor_states["moving_distance"]
+        assert pytest.approx(7.0) in collector.sensor_states["moving_energy"]
+        assert pytest.approx(200.0) in collector.sensor_states["still_distance"]
+        assert pytest.approx(9.0) in collector.sensor_states["still_energy"]
+        assert pytest.approx(400.0) in collector.sensor_states["detection_distance"]
+
+        # Phase 8: both impossible counts were dropped and the frame after them was parsed
+        assert pytest.approx(600.0) in collector.sensor_states["moving_distance"]
+        assert pytest.approx(11.0) in collector.sensor_states["moving_energy"]
+        assert pytest.approx(300.0) in collector.sensor_states["still_distance"]
+        assert pytest.approx(13.0) in collector.sensor_states["still_energy"]
+        assert pytest.approx(600.0) in collector.sensor_states["detection_distance"]
+
         # Verify binary sensors detected targets (from Phase 1 frame)
         assert collector.binary_states["has_target"][0] is True
         assert collector.binary_states["has_moving_target"][0] is True
@@ -524,7 +564,7 @@ async def test_uart_mock_ld2412_truncated_answer(
     def line_callback(line: str) -> None:
         if "[W][ld2412" in line:
             warnings.append(line)
-        if "Dropping gate threshold answer" in line and not dropped.done():
+        if "Invalid length" in line and not dropped.done():
             dropped.set_result(True)
 
     # Gate bytes of the truncated answer
@@ -681,3 +721,56 @@ async def test_uart_mock_ld2412_requery_after_giveup(
         assert gate_0_state.state == pytest.approx(25.0)
         assert gate_5_values
         assert all(value == pytest.approx(30.0) for value in gate_5_values)
+
+
+@pytest.mark.asyncio
+async def test_uart_mock_ld2412_short_answers(
+    yaml_config: str,
+    run_compiled: RunCompiledFunction,
+    api_client_connected: APIClientConnectedFactory,
+) -> None:
+    """Test that answers cut short publish nothing and the whole answers after them do."""
+    loop = asyncio.get_running_loop()
+    # Number object_id: the value from the whole basic configuration answer
+    expected = {"min_distance_gate": 3.0, "max_distance_gate": 8.0, "timeout": 10.0}
+    number_states: dict[str, list[float]] = {name: [] for name in expected}
+    version_states: list[str] = []
+    key_to_name: dict[int, str] = {}
+    all_received = loop.create_future()
+
+    def on_state(state: EntityState) -> None:
+        if isinstance(state, TextSensorState) and not state.missing_state:
+            version_states.append(state.state)
+        elif (
+            isinstance(state, NumberState)
+            and not state.missing_state
+            and (name := key_to_name.get(state.key)) is not None
+        ):
+            number_states[name].append(state.state)
+        if not all_received.done() and version_states and all(number_states.values()):
+            all_received.set_result(True)
+
+    async with (
+        run_compiled(yaml_config),
+        api_client_connected() as client,
+    ):
+        entities, _ = await client.list_entities_services()
+        key_to_name.update(
+            {require_entity(entities, name, NumberInfo).key: name for name in expected}
+        )
+        await _wait_initial(client, entities, on_state)
+
+        start_btn = require_entity(entities, "start_scenario", ButtonInfo)
+        client.button_command(start_btn.key)
+
+        await wait_or_fail(
+            all_received,
+            5.0,
+            "Timeout waiting for the whole answers",
+            number_states=number_states,
+            version_states=version_states,
+        )
+        # Each entity saw exactly one value, the one from the whole answer
+        assert version_states == ["2.07.22062416"]
+        for name, value in expected.items():
+            assert number_states[name] == pytest.approx([value]), name