Điều khiển và Giám sát một thiết bị bằng Smartphone qua BLE với bo mạch VBLUno51

void gattserverWriteCallback(const GattWriteCallbackParams *Handler) {
  
  static uint8_t buf[TXRX_BUF_LEN];
  static uint16_t bytes_read=0;

  if(Handler->handle == led_characteristic.getValueAttribute().getHandle()) {
           
    // Read the value of characteristic
    ble.readCharacteristicValue(led_characteristic.getValueAttribute().getHandle(), 
                                buf, 
                                &bytes_read);       
    if (bytes_read > 0) {                             
      //on LED
      if (buf[0] == 0) {
        digitalWrite(LED, HIGH);
        Serial.println("Turn LED on");
      }
      //off LED
      else {
        digitalWrite(LED, LOW);
        Serial.println("Turn LED off");
      }      
    }//if2
  }//if  
}

//ISR for Button interrupt
void buttonIsr() {   

  button_char_value[0]++;
  
  //push data to Mobile
  ble.updateCharacteristicValue(button_characteristic.getValueAttribute().getHandle(), 
                                (const uint8_t*)button_char_value, 
                                1);
  
  Serial.print("Send data to Mobile via BLE: ");
  Serial.println(button_char_value[0]);                               
}

public class LedButtonGattAttributes {

    /**
     *  brief      UUID cho các services và characteristic
     */
    //Bot service gồm 5 characteristics
    public static final String led_button_service_uuid    = "0000FFF8-0000-1000-8000-00805F9B34FB";
    public static final String led_char_uuid              = "0000FFF9-0000-1000-8000-00805F9B34FB";  //WRITE-uchar
    public static final String button_char_uuid           = "0000FFFA-0000-1000-8000-00805F9B34FB";  //NOTIFY-uchar

    public static final int LED_ON = 0;
    public static final int LED_OFF = 1;

    private static HashMap<String, String> attributes = new HashMap();
    public static String CLIENT_CHARACTERISTIC_CONFIG = "00002902-0000-1000-8000-00805f9b34fb";

    static {
        attributes.put(led_button_service_uuid, "LED_BUTTON_SERVICE");
        attributes.put(led_char_uuid, "LED");
        attributes.put(button_char_uuid, "BUTTON");        
    }

    public static String lookup(String uuid, String defaultName) {
        String name = attributes.get(uuid);
        return name == null ? defaultName : name;
    }
}

/*
     *   @brief:     Hàm ghi giá trị xuống 1 custom characteristic
     */
    public void writeCustomCharacteristic(String serviceUUID,
                                          String charUUID,
                                          int value) {
        if (mBluetoothAdapter == null || mBluetoothGatt == null) {
            Log.w(TAG, "BluetoothAdapter not initialized");
            return;
        }
        /*check if the service is available on the device*/
        BluetoothGattService mCustomService = mBluetoothGatt.getService(UUID.fromString(serviceUUID));
        if(mCustomService == null){
            Log.w(TAG, "Custom BLE Service not found");
            return;
        }
        /*get the read characteristic from the service*/
        BluetoothGattCharacteristic mWriteCharacteristic = mCustomService.getCharacteristic(UUID.fromString(charUUID));
        mWriteCharacteristic.setValue(value,android.bluetooth.BluetoothGattCharacteristic.FORMAT_UINT8,0);
        if(mBluetoothGatt.writeCharacteristic(mWriteCharacteristic) == false){
            Log.w(TAG, "Failed to write characteristic");
        }
    }
    
    /*
    *   @brief:     Hàm cho phép notify theo thông tin UUID của service, characteristic
     */

    public void notifyCustomCharacteristic(String serviceUUID, 
                                           String charUUID, 
                                           boolean state) {

        if (mBluetoothAdapter == null || mBluetoothGatt == null) {
            Log.w(TAG, "BluetoothAdapter not initialized");
            return;
        }

        /*check if the service is available on the device*/
        BluetoothGattService mCustomService = mBluetoothGatt.getService(UUID.fromString(serviceUUID));
        if(mCustomService == null){
            Log.w(TAG, "Custom BLE Service not found");
            return;
        }

        BluetoothGattCharacteristic mCharacteristic = mCustomService.getCharacteristic(UUID.fromString(charUUID));
        setCharacteristicNotification(mCharacteristic, state);

}

/*
     *  @brief      Hành động khi nhấn nút LED
     */
    public void onClickLed(View v){
        if(mBluetoothLeService != null) {
            int value = LedButtonGattAttributes.LED_OFF;
            if (tgbLed.isChecked()) {
                value = LedButtonGattAttributes.LED_ON;
            }
            else {
                value = LedButtonGattAttributes.LED_OFF;
            }

            mBluetoothLeService.writeCustomCharacteristic(
                    LedButtonGattAttributes.led_button_service_uuid,
                    LedButtonGattAttributes.led_char_uuid,
                    value);

            Log.v(TAG, tgbLed.getText().toString());

        }
    }

    /*
     *  @brief      Thủ tục xử lý dữ liệu nhận được từ BLE Device (VBLUno51)
     */
    public void processBleData(String data){
            lblButtonValue.setText("Value: " + data);
}