Bluetooth disconnects when calling writeCharacteristic on Android 13

When I call BleManager.writeCharacteristic where the data has 543 bytes in the array, the call succeeds on Android 12. However, on Android 13 the bluetooth disconnects with the following logs:

2022-09-15 12:59:30.850 V/Android-BLE-Library: Writing characteristic <custom characteristic UUID> (WRITE REQUEST)
2022-09-15 12:59:30.850 D/Android-BLE-Library: gatt.writeCharacteristic(<custom characteristic UUID>)
2022-09-15 12:59:31.685 D/BluetoothAdapter: onBluetoothServiceDown
2022-09-15 12:59:31.692 D/BluetoothAdapter: onBluetoothServiceDown
2022-09-15 12:59:31.695 D/Android-BLE-Library: [Broadcast] Action received: android.bluetooth.adapter.action.STATE_CHANGED, state changed to TURNING OFF
2022-09-15 12:59:31.696 I/Android-BLE-Library: Disconnected
2022-09-15 12:59:31.712 D/Android-BLE-Library: gatt.close()
2022-09-15 12:59:31.712 D/BluetoothGatt: close()
2022-09-15 12:59:31.712 D/BluetoothGatt: unregisterApp() - mClientIf=6
2022-09-15 12:59:31.714 E/BluetoothGatt: android.os.DeadObjectException
        at android.os.BinderProxy.transactNative(Native Method)
        at android.os.BinderProxy.transact(BinderProxy.java:584)
        at android.bluetooth.IBluetoothGatt$Stub$Proxy.unregisterClient(IBluetoothGatt.java:1506)
        at android.bluetooth.BluetoothGatt.unregisterApp(BluetoothGatt.java:941)
        at android.bluetooth.BluetoothGatt.close(BluetoothGatt.java:799)
        at no.nordicsemi.android.ble.BleManagerHandler.close(BleManagerHandler.java:472)
        at no.nordicsemi.android.ble.BleManagerHandler.notifyDeviceDisconnected(BleManagerHandler.java:1633)
        at no.nordicsemi.android.ble.BleManagerHandler.access$900(BleManagerHandler.java:59)
        at no.nordicsemi.android.ble.BleManagerHandler$1.onReceive(BleManagerHandler.java:279)
        at android.app.LoadedApk$ReceiverDispatcher$Args.lambda$getRunnable$0$android-app-LoadedApk$ReceiverDispatcher$Args(LoadedApk.java:1790)
        at android.app.LoadedApk$ReceiverDispatcher$Args$$ExternalSyntheticLambda0.run(Unknown Source:2)
        at android.os.Handler.handleCallback(Handler.java:942)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loopOnce(Looper.java:201)
        at android.os.Looper.loop(Looper.java:288)
        at android.app.ActivityThread.main(ActivityThread.java:7898)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:548)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:936)
2022-09-15 12:59:31.714 D/BleManagerGattCallback: onServicesInvalidated
2022-09-15 12:59:31.714 D/BleManagerGattCallback: onDeviceDisconnected
2022-09-15 12:59:31.995 D/BluetoothAdapter: onBluetoothServiceUp: android.bluetooth.IBluetooth$Stub$Proxy@868fc9d

There are a few earlier calls to writeCharacteristic with 1-2 bytes that succeed, it’s only the call with the larger amount of data that fails due to the bluetooth disconnecting.

For reference, I’m targeting API 32 and using the following library versions:

implementation 'no.nordicsemi.android.support.v18:scanner:1.6.0'
implementation "no.nordicsemi.android:ble:2.5.1"
implementation "no.nordicsemi.android:ble-livedata:2.5.1"

Has anyone else run into this issue on Android 13?

[giampaolo]

Thanks a lot @philips77, that was very helpful.

[giampaolo]

Hi @philips77

Usually, either the first write command contains a full length

Do you know if the first write() is guaranteed to be fully sent as-is even if it’s very small (let’s say 4 bytes)? Is there a risk for it to be sent with subsequent data, when the send buffer is big enough? Basically what I’m asking is if a flush() automatically occurs after every write().