code: private boolean writeToCharacteristic(BluetoothGattCharacteristic charc, byte[] data) {
          charc.setValue(data);
          boolean result = mGattClient.writeCharacteristic(charc);
          if (result) {
              Log.d(TAG, "Wrote to characteristic: " + charc.getUuid() +
                      ", data: " + Arrays.toString(data));
          } else {
              Log.e(TAG, "Write failed to characteristic: " + charc.getUuid() +
                      ", data: " + Arrays.toString(data));
          }
          return result;
      }
docs: Write to a OAD characteristic
  
  @param charc The characteristic being inspected
  @return      true if it's the OAD Block characteristic