Acknowledged
3 months ago

Bug report: BLE: Get data from "indicate" characteristics not working

I develop a data field to connect the Garmin watches to a treadmill series of a specific manufacturer.
The transmitted data and commands are the same for all models, but while the most models are using notifications, atleast one model, with a different Bluetooth controller is using indications.

Sending data to the treadmill works without problem, but receiving data doesn't work - onCharacteristicChanged is never called.

I don't own this model by myself, which makes debugging a bit harder. Fortunately, a user is very nice and helps me testing - unfortunately with little success.

I've created a testing website using Web Bluetooth API and here, everything works perfect.
I've implemented some logging, it would be nice if a Bluetooth API expert would take a look into that.

These are the BLE related functions which I call, and the comments are the events which are called by the system:
(to focus on the important parts, I've removed null-checks/error handling etc.)

BluetoothLowEnergy.setScanState(BluetoothLowEnergy.SCAN_STATE_SCANNING);

// onScanStateChange(1, STATUS_SUCCESS)

// onScanResults()

// -> Device found

BluetoothLowEnergy.setScanState(BluetoothLowEnergy.SCAN_STATE_OFF);

var profile = {
  :uuid => serviceUuid,
  :characteristics => [
    {
      :uuid => readCharacteristicUuid,
      :descriptors => [BluetoothLowEnergy.cccdUuid()]
    },
    {
      :uuid => writeCharacteristicUuid
    }
  ]
};

BluetoothLowEnergy.registerProfile(profile);

BluetoothLowEnergy.pairDevice(scanResult);

// onProfileRegister(0000FEE7-0000-1000-8000-00805F9B34FB, STATUS_SUCCESS)

// onScanStateChange(0, STATUS_SUCCESS)

// onConnectedStateChanged({ isConnected: true }, CONNECTION_STATE_CONNECTED)

var service = device.getService(serviceUuid);
var readCharacteristic = service.getCharacteristic(readCharacteristicUuid);
var descriptor = readCharacteristic.getDescriptor(BluetoothLowEnergy.cccdUuid());
descriptor.requestWrite([0x02, 0x00]b);

// onDescriptorWrite(00002902-0000-1000-8000-00805F9B34FB, STATUS_SUCCESS)

var service = device.getService(serviceUuid);
var writeCharacteristic = service.getCharacteristic(writeCharacteristicUuid);
writeCharacteristic.requestWrite(self.prepareDataRequest(), { :writeType => BluetoothLowEnergy.WRITE_TYPE_DEFAULT });

// onCharacteristicWrite(0000FE02-0000-1000-8000-00805F9B34FB, STATUS_SUCCESS)

The prepareDataRequest method prepares a ByteArray which tells the treadmill to send status data.

That's it ... the data field is now waiting for data but onCharacteristicChanged is never called.

The same code with notifications on another treadmill model (and descriptor.requestWrite([0x01, 0x00]b);) works without problems.

I've also tried writeType => BluetoothLowEnergy.WRITE_TYPE_WITH_RESPONSE, and while this works for my model, it fails with onCharacteristicWrite(0000FE02-0000-1000-8000-00805F9B34FB, STATUS_WRITE_FAIL)on the users model.

Regarding the documention, if I set the CCCD flag for "indicate", the watch will take care about the rest and onCharacteristicChanged should be called:

After enabling notifications or indications on a characteristic by enabling the appropriate bit of the CCCD of the characteristic this function will be called after every change to the characteristic.

So I guess this is a general problem with Indications.

Many regards,
Jens

JensDuttke