code: private int readVersion(@Nullable final BluetoothGattCharacteristic characteristic) {
  		// The value of this characteristic has been read before by LegacyButtonlessDfuImpl
  		return characteristic != null ? characteristic.getIntValue(BluetoothGattCharacteristic.FORMAT_UINT16, 0) : 0;
  	}
docs: Returns the DFU Version characteristic if such exists. Otherwise it returns 0.
  
  @param characteristic the characteristic to read.
  @return a version number or 0 if not present on the bootloader.