@Override
 public void onCharacteristicChanged(
     BluetoothGatt gatt, BluetoothGattCharacteristic characteristic) {
   if (DEBUG) Log.d(TAG, "onCharacteristicChanged: " + characteristic.toString());
   final byte[] data = characteristic.getValue();
   inTalkStream.write(data);
 }
  private void receiveData(String data) {
    // if (DEBUG) Log.d(TAG, "Received data: " + data);

    inTalkStream.write(data.getBytes());
    inTalkStream.notify();
  }