Switch to connect→poll→disconnect per cycle (single-connection BMS fix)

The BMS only allows one simultaneous BLE connection. Keeping a persistent
connection blocked the mobile app from connecting at all.

Changes:
- BmsBluetoothHandler: replace connect()/disconnect()/request() public API
  with a single poll() method that owns the full connect→read→disconnect
  lifecycle. Connection is held only for the duration of one data fetch.
- Coordinator: gutted connection-state management — _async_update_data now
  just calls handler.poll() and processes results. No reconnect loop needed.
- Poll interval defaults: 15s default, 10s min, 300s max. The BLE connect
  overhead (~2s) makes sub-10s intervals impractical.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

custom_components/xiaoxiang_bms/bluetooth_handler.py

@@ -25,67 +25,55 @@ _TRAILER_LEN = 3
 
 
 class BmsBluetoothHandler:
-    """Manages BLE connection and protocol framing for a Xiaoxiang BMS device."""
+    """Protocol framing and parsing for a Xiaoxiang BMS device.
+
+    Designed for a connect → poll → disconnect pattern: the BMS only allows
+    one simultaneous BLE connection, so we hold it only for the duration of
+    a single data fetch and release it immediately after.
+    """
 
     def __init__(self, address: str) -> None:
         self._address = address
-        self._client: BleakClient | None = None
         self._buffer = bytearray()
         self._response_event = asyncio.Event()
         self._response_data: bytes | None = None
         self._lock = asyncio.Lock()
 
     # ------------------------------------------------------------------
-    # Connection management
+    # High-level poll — the only entry point the coordinator needs
     # ------------------------------------------------------------------
 
-    @property
+    async def poll(
-    def is_connected(self) -> bool:
+        self,
-        return self._client is not None and self._client.is_connected
+        ble_device: BLEDevice,
+        commands: list[bytes],
+        timeout: float = 5.0,
+        retries: int = 3,
+    ) -> list[bytes | None]:
+        """Connect, send each command in sequence, disconnect.
 
-    async def connect(self, ble_device: BLEDevice) -> None:
+        The BMS only supports a single BLE connection at a time. By connecting
-        """Open BLE connection and start notifications.
+        only during the active read window and disconnecting immediately after,
-
+        the mobile app (or any other client) can connect freely between polls.
-        Accepts a BLEDevice resolved by HA's Bluetooth subsystem so that
-        ESPHome BLE proxies are used transparently alongside local adapters.
         """
-        if self.is_connected:
+        _LOGGER.debug("Polling BMS at %s", self._address)
-            return
+        client = BleakClient(ble_device)
-        _LOGGER.debug("Connecting to BMS at %s (via %s)", self._address, ble_device.name)
-        client = BleakClient(
-            ble_device,
-            disconnected_callback=self._on_disconnect,
-        )
         try:
             await client.connect()
             await client.start_notify(RX_CHAR_UUID, self._on_notify)
-        except Exception:
+            # Give the BMS a moment to register the subscription before
-            # Ensure a failed connect never leaves a broken client behind —
+            # we start sending commands
-            # next poll will start fresh
+            await asyncio.sleep(0.5)
+            return [
+                await self._request(client, cmd, timeout, retries)
+                for cmd in commands
+            ]
+        finally:
             try:
                 await client.disconnect()
             except Exception:
                 pass
-            self._client = None
+            self._buffer.clear()
-            raise
-        # Give the BMS a moment to register the notification subscription
-        # before we start sending commands — avoids dropped first response
-        self._client = client
-        await asyncio.sleep(0.5)
-        _LOGGER.debug("Connected to BMS at %s", self._address)
-
-    async def disconnect(self) -> None:
-        """Close the BLE connection cleanly."""
-        if self._client:
-            try:
-                await self._client.disconnect()
-            except Exception:
-                pass
-            self._client = None
-
-    def _on_disconnect(self, _client: BleakClient) -> None:
-        _LOGGER.debug("BMS at %s disconnected", self._address)
-        self._client = None
 
     # ------------------------------------------------------------------
     # Frame reception
@@ -131,36 +119,30 @@ class BmsBluetoothHandler:
         self._response_event.set()
 
     # ------------------------------------------------------------------
-    # Request / response
+    # Request / response (private — used inside poll())
     # ------------------------------------------------------------------
 
-    async def request(
+    async def _request(
         self,
+        client: BleakClient,
         command: bytes,
-        timeout: float = 5.0,
+        timeout: float,
-        retries: int = 3,
+        retries: int,
     ) -> bytes | None:
-        """Send a command frame and wait for the corresponding response frame.
+        """Send one command and wait for the response frame, with retries.
 
-        Retries up to `retries` times with a short pause between attempts to
+        Tries Write With Response first; falls back to Write Without Response
-        handle occasional BLE packet loss or a slow BMS response.
+        if the characteristic rejects it — covers both BMS firmware variants.
-        Tries Write With Response first; if that raises a GATT error the BMS
-        likely only supports Write Without Response, so we fall back silently.
         """
         async with self._lock:
             for attempt in range(1, retries + 1):
                 self._response_event.clear()
                 self._response_data = None
                 try:
-                    await self._client.write_gatt_char(
+                    await client.write_gatt_char(TX_CHAR_UUID, command, response=True)
-                        TX_CHAR_UUID, command, response=True
-                    )
                 except BleakError:
-                    # Characteristic may not support Write With Response — try without
                     try:
-                        await self._client.write_gatt_char(
+                        await client.write_gatt_char(TX_CHAR_UUID, command, response=False)
-                            TX_CHAR_UUID, command, response=False
-                        )
                     except BleakError as exc:
                         _LOGGER.error("BLE write failed (attempt %d/%d): %s",
                                       attempt, retries, exc)
@@ -172,10 +154,8 @@ class BmsBluetoothHandler:
                     await asyncio.wait_for(self._response_event.wait(), timeout)
                     return self._response_data
                 except asyncio.TimeoutError:
-                    _LOGGER.warning(
+                    _LOGGER.warning("BMS timeout (cmd=0x%s, attempt %d/%d)",
-                        "BMS response timeout (cmd=0x%s, attempt %d/%d)",
+                                    command.hex(), attempt, retries)
-                        command.hex(), attempt, retries,
-                    )
                     if attempt < retries:
                         await asyncio.sleep(0.5)
 

custom_components/xiaoxiang_bms/const.py

@@ -5,9 +5,9 @@ DOMAIN = "xiaoxiang_bms"
 CONF_ADDRESS = "address"
 CONF_POLL_INTERVAL = "poll_interval"
 
-DEFAULT_POLL_INTERVAL = 5   # seconds — fast for solar/energy monitoring
+DEFAULT_POLL_INTERVAL = 15  # seconds — each poll does a full BLE connect/disconnect
-MIN_POLL_INTERVAL = 2
+MIN_POLL_INTERVAL = 10      # below this the BMS has no breathing room between polls
-MAX_POLL_INTERVAL = 60
+MAX_POLL_INTERVAL = 300
 
 # GATT UUIDs (Xiaoxiang BMS UART-over-GATT)
 UART_SERVICE_UUID = "0000ff00-0000-1000-8000-00805f9b34fb"

custom_components/xiaoxiang_bms/coordinator.py

@@ -16,7 +16,11 @@ _LOGGER = logging.getLogger(__name__)
 
 
 class BmsCoordinator(DataUpdateCoordinator[dict]):
-    """Polls the BMS over BLE and distributes data to all sensor entities."""
+    """Polls the BMS over BLE and distributes data to all sensor entities.
+
+    Uses a connect → read → disconnect pattern on every poll so the BMS's
+    single BLE connection slot is free between updates (mobile app access).
+    """
 
     def __init__(
         self,
@@ -32,10 +36,10 @@ class BmsCoordinator(DataUpdateCoordinator[dict]):
         )
         self.address = address
         self._handler = BmsBluetoothHandler(address)
-        self.hw_version: str | None = None  # populated on first successful poll
+        self.hw_version: str | None = None
 
     # ------------------------------------------------------------------
-    # Device info — centralised so sensor + binary_sensor share it
+    # Device info — shared by sensor, binary_sensor, number platforms
     # ------------------------------------------------------------------
 
     @property
@@ -51,60 +55,44 @@ class BmsCoordinator(DataUpdateCoordinator[dict]):
     # Lifecycle
     # ------------------------------------------------------------------
 
-    def _get_ble_device(self):
-        """Resolve the best available BLE device via HA's Bluetooth subsystem.
-
-        Automatically uses ESPHome BLE proxies if they can reach the BMS.
-        """
-        device = async_ble_device_from_address(self.hass, self.address, connectable=True)
-        if device is None:
-            raise UpdateFailed(
-                f"BMS ({self.address}) not reachable by any Bluetooth adapter or proxy"
-            )
-        return device
-
     async def async_setup(self) -> None:
-        """No-op — connection is established lazily on the first poll."""
+        """No-op — no persistent connection to establish."""
 
     async def async_teardown(self) -> None:
-        """Disconnect cleanly. Called on entry unload."""
+        """No-op — each poll disconnects itself."""
-        await self._handler.disconnect()
 
     # ------------------------------------------------------------------
     # Poll
     # ------------------------------------------------------------------
 
     async def _async_update_data(self) -> dict:
-        """Fetch data from the BMS. Reconnects automatically if disconnected."""
+        """Connect to the BMS, fetch all data, disconnect."""
-        if not self._handler.is_connected:
+        device = async_ble_device_from_address(self.hass, self.address, connectable=True)
-            _LOGGER.debug("BMS not connected, attempting reconnect…")
+        if device is None:
-            try:
+            raise UpdateFailed(
-                await self._handler.connect(self._get_ble_device())
+                f"BMS ({self.address}) not reachable — check Bluetooth adapter / proxy"
-            except UpdateFailed:
+            )
-                raise
+
-            except Exception as exc:
+        # Fetch hardware version once; skip on subsequent polls
-                raise UpdateFailed(f"BMS reconnect failed: {exc}") from exc
+        commands = [CMD_GENERAL, CMD_CELL]
+        if self.hw_version is None:
+            commands.append(CMD_VERSION)
 
         try:
-            general_frame = await self._handler.request(CMD_GENERAL)
+            responses = await self._handler.poll(device, commands)
-            if general_frame is None:
-                raise UpdateFailed("No response to general info request (0x03)")
-
-            cell_frame = await self._handler.request(CMD_CELL)
-            if cell_frame is None:
-                raise UpdateFailed("No response to cell info request (0x04)")
-
-            # Fetch hardware version string once — used in DeviceInfo model field
-            if self.hw_version is None:
-                version_frame = await self._handler.request(CMD_VERSION)
-                if version_frame:
-                    self.hw_version = BmsBluetoothHandler.parse_version(version_frame)
-                    _LOGGER.debug("BMS hardware version: %s", self.hw_version)
-
-        except UpdateFailed:
-            raise
         except Exception as exc:
-            raise UpdateFailed(f"BLE communication error: {exc}") from exc
+            raise UpdateFailed(f"BMS poll failed: {exc}") from exc
+
+        general_frame, cell_frame = responses[0], responses[1]
+
+        if general_frame is None:
+            raise UpdateFailed("No response to general info request (0x03)")
+        if cell_frame is None:
+            raise UpdateFailed("No response to cell info request (0x04)")
+
+        if self.hw_version is None and len(responses) > 2 and responses[2]:
+            self.hw_version = BmsBluetoothHandler.parse_version(responses[2])
+            _LOGGER.debug("BMS hardware version: %s", self.hw_version)
 
         data = BmsBluetoothHandler.parse_general_info(general_frame)
         data.update(BmsBluetoothHandler.parse_cell_info(cell_frame))
@@ -122,11 +110,8 @@ class BmsCoordinator(DataUpdateCoordinator[dict]):
 
         _LOGGER.debug(
             "BMS data: %.2fV  %.2fA  %d%%  %.2fAh  %.3fkWh  %d cells",
-            data["voltage"],
+            data["voltage"], data["current"], data["state_of_charge"],
-            data["current"],
+            data["residual_capacity"], data["energy_stored"],
-            data["state_of_charge"],
-            data["residual_capacity"],
-            data["energy_stored"],
             len(data["cell_voltages"]),
         )
         return data