[esp32_ble_tracker] Scan at the default window while a GATT connection is active

esphome/components/ble_device_base/__init__.py

@@ -211,10 +211,19 @@ def validate_scan_parameters(config: ConfigType) -> ConfigType:
             f"Scan window ({window}) needs to be smaller than scan interval ({interval})"
         )
 
+    windows = [("window", window)]
+    if (connection_window := config.get(CONF_CONNECTION_SCAN_WINDOW)) is not None:
+        if connection_window > interval:
+            raise cv.Invalid(
+                f"Connection scan window ({connection_window}) needs to be smaller "
+                f"than scan interval ({interval})"
+            )
+        windows.append(("connection window", connection_window))
+
     # BLE scan interval/window are programmed in 0.625 ms units as a 16-bit value; the
     # controller only accepts 2.5 ms .. 10240 ms (0x0004 .. 0x4000). Reject out-of-range
     # values here instead of letting the unit conversion silently overflow.
-    for name, value in (("interval", interval), ("window", window)):
+    for name, value in (("interval", interval), *windows):
         if value.total_microseconds < 2500 or value.total_microseconds > 10_240_000:
             raise cv.Invalid(
                 f"Scan {name} ({value}) must be between 2.5 ms and 10240 ms"
@@ -247,11 +256,14 @@ def validate_scan_parameters(config: ConfigType) -> ConfigType:
 # their own; also the fallback for esp32's conditional default.
 DEFAULT_SCAN_WINDOW = "30ms"
 
+CONF_CONNECTION_SCAN_WINDOW = "connection_scan_window"
+
 
 def scan_parameters_schema(
     interval_default: str,
     *,
     window_default: str | Callable[[], TimePeriod] = DEFAULT_SCAN_WINDOW,
+    connection_window: bool = False,
 ) -> cv.All:
     """Build the scan_parameters value schema shared by all BLE trackers.
 
@@ -263,7 +275,9 @@ def scan_parameters_schema(
     can adjust it once sibling keys are resolved). The `active` option
     (default on) is unconditional: active scanning is part of the tracker
     contract — every current proxy client assumes it, so a passive-only
-    tracker must not share this schema.
+    tracker must not share this schema. connection_window opts in to the
+    `connection_scan_window` option for trackers that can fall back to a
+    smaller window while a GATT connection is active.
     """
     schema = {
         cv.Optional(CONF_DURATION, default="5min"): cv.positive_time_period_seconds,
@@ -272,6 +286,8 @@ def scan_parameters_schema(
         cv.Optional(CONF_CONTINUOUS, default=True): cv.boolean,
         cv.Optional(CONF_ACTIVE, default=True): cv.boolean,
     }
+    if connection_window:
+        schema[cv.Optional(CONF_CONNECTION_SCAN_WINDOW)] = cv.positive_time_period
     return cv.All(cv.Schema(schema), validate_scan_parameters)
 
 

esphome/components/esp32_ble_tracker/__init__.py

@@ -7,6 +7,7 @@ import logging
 from esphome import automation
 import esphome.codegen as cg
 from esphome.components import ble_device_base, esp32_ble, ota
+from esphome.components.ble_device_base import CONF_CONNECTION_SCAN_WINDOW
 from esphome.components.const import CONF_ON_SCAN_END, CONF_SCAN_PARAMETERS, CONF_WINDOW
 from esphome.components.esp32 import (
     add_idf_sdkconfig_option,
@@ -186,6 +187,13 @@ def _raise_defaulted_scan_window(config: ConfigType) -> ConfigType:
         # Copy so the config dump shows a plain value instead of a YAML
         # anchor/alias pair pointing at the interval.
         params[CONF_WINDOW] = copy.copy(params[CONF_INTERVAL])
+        # A full-duty scan must not compete with an active GATT connection
+        # for airtime, so arm the connection-time fallback window as well
+        # unless the user picked one themselves.
+        if CONF_CONNECTION_SCAN_WINDOW not in params:
+            params[CONF_CONNECTION_SCAN_WINDOW] = cv.positive_time_period(
+                ble_device_base.DEFAULT_SCAN_WINDOW
+            )
     return config
 
 
@@ -194,7 +202,7 @@ def _raise_defaulted_scan_window(config: ConfigType) -> ConfigType:
 # window/interval pairs that collapse to the same 0.625 ms unit count.
 # The window default is conditional (see _scan_window_default above).
 SCAN_PARAMETERS_SCHEMA = ble_device_base.scan_parameters_schema(
-    "320ms", window_default=_scan_window_default
+    "320ms", window_default=_scan_window_default, connection_window=True
 )
 
 # Codegen helpers are owned by ble_device_base; kept under the historical names
@@ -288,6 +296,15 @@ async def to_code(config: ConfigType) -> None:
     cg.add(var.set_scan_duration(params[CONF_DURATION]))
     cg.add(var.set_scan_interval(ble_device_base.to_ble_units(params[CONF_INTERVAL])))
     cg.add(var.set_scan_window(ble_device_base.to_ble_units(params[CONF_WINDOW])))
+    if (connection_window := params.get(CONF_CONNECTION_SCAN_WINDOW)) is not None:
+        # Set by the user, or defaulted by _raise_defaulted_scan_window when
+        # the window was raised to full duty; while a GATT connection is
+        # active the scanner falls back to it (see start_scan_).
+        cg.add(
+            var.set_connection_scan_window(
+                ble_device_base.to_ble_units(connection_window)
+            )
+        )
     cg.add(var.set_scan_active(params[CONF_ACTIVE]))
     cg.add(var.set_scan_continuous(params[CONF_CONTINUOUS]))
 

esphome/components/esp32_ble_tracker/esp32_ble_tracker.cpp

@@ -247,7 +247,16 @@ void ESP32BLETracker::start_scan_(bool first) {
   this->scan_params_.own_addr_type = BLE_ADDR_TYPE_PUBLIC;
   this->scan_params_.scan_filter_policy = BLE_SCAN_FILTER_ALLOW_ALL;
   this->scan_params_.scan_interval = this->scan_interval_;
-  this->scan_params_.scan_window = this->scan_window_;
+  uint32_t window = this->scan_window_;
+  if (this->connection_scan_window_ != 0 && this->client_state_counts_.active > 0) {
+    // The defaulted window was raised to full duty for advertisement
+    // throughput; while a GATT connection is active, fall back so the
+    // connection events get guaranteed airtime instead of competing with
+    // a wall-to-wall scan on the shared radio.
+    ESP_LOGV(TAG, "Connection active, using %" PRIu32 " unit scan window", this->connection_scan_window_);
+    window = this->connection_scan_window_;
+  }
+  this->scan_params_.scan_window = window;
 
   // Start timeout monitoring in loop() instead of using scheduler
   // This prevents false reboots when the loop is blocked

esphome/components/esp32_ble_tracker/esp32_ble_tracker.h

@@ -169,6 +169,7 @@ class ESP32BLETracker final : public Component,
   void set_scan_duration(uint32_t scan_duration) { scan_duration_ = scan_duration; }
   void set_scan_interval(uint32_t scan_interval) { scan_interval_ = scan_interval; }
   void set_scan_window(uint32_t scan_window) { scan_window_ = scan_window; }
+  void set_connection_scan_window(uint32_t scan_window) { connection_scan_window_ = scan_window; }
   void set_scan_active(bool scan_active) { scan_active_ = scan_active; }
   bool get_scan_active() const { return scan_active_; }
   void set_scan_continuous(bool scan_continuous) { scan_continuous_ = scan_continuous; }
@@ -313,6 +314,9 @@ class ESP32BLETracker final : public Component,
   uint32_t scan_duration_;
   uint32_t scan_interval_;
   uint32_t scan_window_;
+  /// Window used while a GATT connection is active; only set when the
+  /// defaulted window was raised to full duty (0 = no fallback).
+  uint32_t connection_scan_window_{0};
   esp_bt_status_t scan_start_failed_{ESP_BT_STATUS_SUCCESS};
   esp_bt_status_t scan_set_param_failed_{ESP_BT_STATUS_SUCCESS};
 

tests/component_tests/esp32_ble_tracker/config/scan_window_explicit.yaml

@@ -0,0 +1,14 @@
+esphome:
+  name: scan-window-explicit
+
+esp32:
+  board: esp32dev
+  framework:
+    type: esp-idf
+
+wifi:
+  ssid: MySSID
+
+esp32_ble_tracker:
+  scan_parameters:
+    window: 30ms

tests/component_tests/esp32_ble_tracker/config/scan_window_raised.yaml

@@ -0,0 +1,12 @@
+esphome:
+  name: scan-window-raised
+
+esp32:
+  board: esp32dev
+  framework:
+    type: esp-idf
+
+wifi:
+  ssid: MySSID
+
+esp32_ble_tracker:

tests/component_tests/esp32_ble_tracker/test_scan_window_default.py

@@ -12,11 +12,12 @@ arbiter a full-duty scan would starve wifi, so the 30 ms default is kept.
 from __future__ import annotations
 
 from collections.abc import Callable
+from pathlib import Path
 
 import pytest
 
 from esphome import config_validation as cv
-from esphome.components.ble_device_base import to_ble_units
+from esphome.components.ble_device_base import CONF_CONNECTION_SCAN_WINDOW, to_ble_units
 from esphome.components.const import CONF_SCAN_PARAMETERS, CONF_WINDOW
 from esphome.components.esp32 import KEY_IDF_VERSION
 from esphome.components.esp32_ble_tracker import (
@@ -120,3 +121,61 @@ def test_short_interval_without_window_still_rejected(
     stage_esp32("5.5.5", wifi=True)
     with pytest.raises(cv.Invalid, match="needs to be smaller than scan interval"):
         _scan_params({"scan_parameters": {"interval": "20ms"}})
+
+
+# The connection-time fallback window: while a GATT connection is active the
+# scanner drops from a raised full-duty window back to this value so the
+# connection gets guaranteed airtime.
+
+
+def test_raise_arms_connection_scan_window_default(
+    stage_esp32: Callable[..., None],
+) -> None:
+    stage_esp32("5.5.5", wifi=True)
+    params = _scan_params({})
+    assert params[CONF_WINDOW] == params[CONF_INTERVAL]
+    assert to_ble_units(params[CONF_CONNECTION_SCAN_WINDOW]) == 48
+
+
+def test_user_connection_scan_window_survives_raise(
+    stage_esp32: Callable[..., None],
+) -> None:
+    stage_esp32("5.5.5", wifi=True)
+    params = _scan_params({"scan_parameters": {"connection_scan_window": "60ms"}})
+    assert params[CONF_WINDOW] == params[CONF_INTERVAL]
+    assert to_ble_units(params[CONF_CONNECTION_SCAN_WINDOW]) == 96
+
+
+def test_unraised_window_gets_no_connection_scan_window_default(
+    stage_esp32: Callable[..., None],
+) -> None:
+    stage_esp32("5.5.4", wifi=True)
+    assert CONF_CONNECTION_SCAN_WINDOW not in _scan_params({})
+
+
+def test_connection_scan_window_above_interval_rejected(
+    stage_esp32: Callable[..., None],
+) -> None:
+    stage_esp32("5.5.5", wifi=True)
+    with pytest.raises(
+        cv.Invalid, match="Connection scan window .* needs to be smaller"
+    ):
+        _scan_params({"scan_parameters": {"connection_scan_window": "400ms"}})
+
+
+def test_codegen_connection_window_when_raised(
+    generate_main: Callable[[str | Path], str],
+    component_config_path: Callable[[str], Path],
+) -> None:
+    main_cpp = generate_main(component_config_path("scan_window_raised.yaml"))
+    assert "set_scan_window(512)" in main_cpp
+    assert "set_connection_scan_window(48)" in main_cpp
+
+
+def test_codegen_no_connection_window_for_explicit_window(
+    generate_main: Callable[[str | Path], str],
+    component_config_path: Callable[[str], Path],
+) -> None:
+    main_cpp = generate_main(component_config_path("scan_window_explicit.yaml"))
+    assert "set_scan_window(48)" in main_cpp
+    assert "set_connection_scan_window" not in main_cpp