public void doWrite(BluetoothGattCharacteristic characteristic, byte[] data) {

    // Log.d(LOG_TAG, "doWrite");

    characteristic.setValue(data);

    if (gatt.writeCharacteristic(characteristic)) {
      // Log.d(LOG_TAG, "doWrite completato");
    } else {
      Log.d(LOG_TAG, "errore doWrite");
    }
  }
  public void write(
      UUID serviceUUID,
      UUID characteristicUUID,
      byte[] data,
      Callback successCallback,
      Callback failCallback,
      int writeType) {

    Log.d(LOG_TAG, "write interno peripheral");

    if (gatt == null) {
      failCallback.invoke("BluetoothGatt is null");

    } else {

      BluetoothGattService service = gatt.getService(serviceUUID);
      BluetoothGattCharacteristic characteristic =
          findWritableCharacteristic(service, characteristicUUID, writeType);
      characteristic.setWriteType(writeType);

      if (characteristic == null) {
        failCallback.invoke("Characteristic " + characteristicUUID + " not found.");
      } else {

        if (writeQueue.size() > 0) {
          failCallback.invoke("Scrittura con byte ancora in coda");
        }

        if (writeCallback != null) {
          failCallback.invoke("Altra scrittura in corso");
        }

        if (writeQueue.size() == 0 && writeCallback == null) {

          if (BluetoothGattCharacteristic.WRITE_TYPE_DEFAULT == writeType) {
            writeCallback = successCallback;
            writeFailCallback = failCallback;
          } else successCallback.invoke();

          if (data.length > 20) {
            int dataLength = data.length;
            int count = 0;
            byte[] firstMessage = null;
            while (count < dataLength && (dataLength - count > 20)) {
              if (count == 0) {
                firstMessage = Arrays.copyOfRange(data, count, count + 20);
              } else {
                byte[] splitMessage = Arrays.copyOfRange(data, count, count + 20);
                writeQueue.add(splitMessage);
              }
              count += 20;
            }
            if (count < dataLength) {
              // Rimangono byte in coda
              byte[] splitMessage = Arrays.copyOfRange(data, count, data.length);
              Log.d(LOG_TAG, "Lunghezza ultimo messaggio: " + splitMessage.length);
              writeQueue.add(splitMessage);
            }

            Log.d(LOG_TAG, "Messaggi in coda: " + writeQueue.size());
            doWrite(characteristic, firstMessage);
          } else {
            characteristic.setValue(data);

            if (gatt.writeCharacteristic(characteristic)) {
              Log.d(LOG_TAG, "write completato");
            } else {
              writeCallback = null;
              failCallback.invoke("Write failed");
            }
          }
        }
      }
    }
  }