From bb27928f92b3edac275ce00c8624ee15a1153080 Mon Sep 17 00:00:00 2001 From: Dave Kneeland Date: Tue, 25 Aug 2026 16:44:35 -0700 Subject: [PATCH] fix(android): retry GATT subscribes dropped by CCCD-busy races Android's GATT client allows one operation in flight; a CCCD write that races another subscribe is silently refused, leaving CAN notifications dead until reconnect. Replace the fire-and-forget descriptor write in DashKitDataSource with DashKitBleManager .subscribeWithRetry(), which verifies the write was queued and retries (up to 3x, 250ms apart). The helper is shared and will also back the Tesla status subscription. --- .../dashpilot/datasource/DashKitBleManager.kt | 41 +++++++++++++++++++ .../dashpilot/datasource/DashKitDataSource.kt | 16 +------- 2 files changed, 42 insertions(+), 15 deletions(-) diff --git a/dashpilot-android/app/src/main/java/com/softwiredtech/dashpilot/datasource/DashKitBleManager.kt b/dashpilot-android/app/src/main/java/com/softwiredtech/dashpilot/datasource/DashKitBleManager.kt index 968a4ce9..fc5f744b 100644 --- a/dashpilot-android/app/src/main/java/com/softwiredtech/dashpilot/datasource/DashKitBleManager.kt +++ b/dashpilot-android/app/src/main/java/com/softwiredtech/dashpilot/datasource/DashKitBleManager.kt @@ -20,6 +20,7 @@ import android.os.Handler import android.os.Looper import android.util.Log import com.google.firebase.crashlytics.FirebaseCrashlytics +import java.util.UUID import com.softwiredtech.dashpilot.ble.VehicleControl import kotlinx.coroutines.flow.MutableStateFlow import kotlinx.coroutines.flow.StateFlow @@ -67,6 +68,12 @@ class DashKitBleManager(private val context: Context) { // Keepalive interval; the firmware drops the link after 60 s without a // ping (KEEPALIVE_TIMEOUT_S), so this allows a few missed writes. private const val PING_INTERVAL_MS = 15_000L + + // Android's GATT client allows only one operation in flight, so a CCCD + // write racing another subscribe can be refused; retry a few times. + private val CCCD_UUID = UUID.fromString("00002902-0000-1000-8000-00805f9b34fb") + private const val MAX_SUBSCRIBE_ATTEMPTS = 3 + private const val SUBSCRIBE_RETRY_DELAY_MS = 250L } private val crashlytics = FirebaseCrashlytics.getInstance() @@ -624,4 +631,38 @@ class DashKitBleManager(private val context: Context) { } catch (_: Exception) {} scanning = false } + + /** Subscribes to a characteristic's notifications, retrying if the CCCD + * write races another GATT operation. Shared by the CAN and Tesla status + * sources. */ + fun subscribeWithRetry( + gatt: BluetoothGatt, + characteristic: BluetoothGattCharacteristic, + logTag: String, + label: String + ) { + val descriptor = characteristic.getDescriptor(CCCD_UUID) + if (descriptor == null) { + Log.e(logTag, "$label CCCD (0x2902) not discovered") + return + } + var attempt = 0 + fun writeCccd() { + val queued = if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU) { + gatt.writeDescriptor(descriptor, BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE) == + BluetoothGatt.GATT_SUCCESS + } else { + @Suppress("DEPRECATION") + descriptor.value = BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE + @Suppress("DEPRECATION") + gatt.writeDescriptor(descriptor) + } + if (!queued && attempt < MAX_SUBSCRIBE_ATTEMPTS) { + attempt++ + Log.d(logTag, "$label CCCD write not queued (attempt=$attempt); retrying") + handler.postDelayed({ writeCccd() }, SUBSCRIBE_RETRY_DELAY_MS) + } + } + writeCccd() + } } diff --git a/dashpilot-android/app/src/main/java/com/softwiredtech/dashpilot/datasource/DashKitDataSource.kt b/dashpilot-android/app/src/main/java/com/softwiredtech/dashpilot/datasource/DashKitDataSource.kt index 85898d85..29e34b51 100644 --- a/dashpilot-android/app/src/main/java/com/softwiredtech/dashpilot/datasource/DashKitDataSource.kt +++ b/dashpilot-android/app/src/main/java/com/softwiredtech/dashpilot/datasource/DashKitDataSource.kt @@ -3,8 +3,6 @@ package com.softwiredtech.dashpilot.datasource import android.annotation.SuppressLint import android.bluetooth.BluetoothGatt import android.bluetooth.BluetoothGattCharacteristic -import android.bluetooth.BluetoothGattDescriptor -import android.os.Build import android.util.Log import com.softwiredtech.dashpilot.datamodel.dash.CarState import kotlinx.coroutines.flow.Flow @@ -26,7 +24,6 @@ class DashKitDataSource( private const val TAG = "DashKitDataSource" private val SERVICE_UUID = UUID.fromString("CADA0000-CA00-B1E0-B0D6-C000AA0100A1") private val CHAR_UUID = UUID.fromString("CADA0001-CA00-B1E0-B0D6-C000AA0100A1") - private val CCCD_UUID = UUID.fromString("00002902-0000-1000-8000-00805f9b34fb") // The firmware now applies CAN acceptance filtering in hardware (per-bus // MCP251xFD filters), so the app no longer pushes a BLE filter list. } @@ -58,18 +55,7 @@ class DashKitDataSource( return } gatt.setCharacteristicNotification(characteristic, true) - val descriptor = characteristic.getDescriptor(CCCD_UUID) - if (descriptor != null) { - if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU) { - gatt.writeDescriptor(descriptor, BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE) - } else { - @Suppress("DEPRECATION") - descriptor.value = BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE - @Suppress("DEPRECATION") - gatt.writeDescriptor(descriptor) - } - } - Log.d(TAG, "Subscribed to CAN notifications") + manager.subscribeWithRetry(gatt, characteristic, TAG, "CAN") } override fun onCharacteristicChanged(