Receive data from Arduino board to Android application

Question

I'm trying to receive data and print it on a label of my application, but I can not get it. Actually, I have 0 experience with Arduino. It's the first time I see this. I read this tutorial to receive data from an Arduino. In my Arduino I have this code:

#include <SoftwareSerial.h>
const int RX_PIN = 2;
const int TX_PIN = 3;
SoftwareSerial blueTooth(RX_PIN, TX_PIN);
char commandChar;

void setup () {
  Serial.begin(57600);
  Serial.println("Let's start!");
  blueTooth.begin(9600);
  blueTooth.println("Hello, world?");
}

void loop () {
 if (blueTooth.available())
    Serial.write(blueTooth.read());
  if (blueTooth.available())
    blueTooth.write(Serial.read());
}

My Android code is this:

public class MainActivity extends AppCompatActivity {
FrameLayout frame;
GifImageView imagen;
TextView mensaje,debug;
Button boton;
private TextToSpeech talk;
public static StringBuilder sb;
private static final String TAG = "conexionBluetooth";
ConnectedThread mConnectedThread;
BluetoothAdapter blueAdapter;
BluetoothDevice mDevice;
BluetoothSocket mSocket;
Handler handler;

final int MENSAJE_RECIBIDO = 1;
final UUID uuid = UUID.fromString("00001101-0000-1000-8000-00805F9B34FB");
private static String MAC = "00:21:13:02:EA:07";

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    getSupportActionBar().hide();
    setContentView(R.layout.activity_main);
    talk = new TextToSpeech(getApplicationContext(), new TextToSpeech.OnInitListener() {
        @Override
        public void onInit(int i) {
            if(i == TextToSpeech.SUCCESS){
                talk.setLanguage(Locale.US);
                mensajeInicio();
            }
        }
    });
    debug = (TextView) findViewById(R.id.debug);
    mensaje = (TextView) findViewById(R.id.mensajeApp);
    frame = (FrameLayout) findViewById(R.id.androidIc);
    imagen = (GifImageView) findViewById(R.id.imageBluethoot);
    imagen.setVisibility(View.INVISIBLE);
    frame.setVisibility(View.VISIBLE);
    boton = (Button) findViewById(R.id.botonInicio);
    Animation flotarArriba = new TranslateAnimation(
            TranslateAnimation.ABSOLUTE, 0f,
            TranslateAnimation.ABSOLUTE, 0f,
            TranslateAnimation.RELATIVE_TO_PARENT, 0f,
            TranslateAnimation.RELATIVE_TO_PARENT, 0.05f
    );
    flotarArriba.setDuration(1000);
    flotarArriba.setRepeatCount(-1);
    flotarArriba.setRepeatMode(Animation.REVERSE);
    flotarArriba.setInterpolator(new LinearInterpolator());
    mensaje.setAnimation(flotarArriba);
    boton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            boton.setEnabled(false);
            mConnectedThread.write("0");
            Toast.makeText(getApplicationContext(),"Data send to arduino",Toast.LENGTH_LONG).show();
        }
    });
    handler = new Handler(){
        public void handleMessage(Message msg) {
            switch (msg.what) {
                case MENSAJE_RECIBIDO:
                    byte[] readBuf = (byte[]) msg.obj;
                    String strIncom = new String(readBuf, 0, msg.arg1);
                    sb.append(strIncom);
                    int endOfLineIndex = sb.indexOf("\r\n");
                    if (endOfLineIndex > 0) {
                        String sbprint = sb.substring(0, endOfLineIndex);
                        sb.delete(0, sb.length());
                        debug.setText(sbprint);
                        boton.setEnabled(true);
                    }
                    //Log.d(TAG, "...String:"+ sb.toString() +  "Byte:" + msg.arg1 + "...");
                    break;
            }
    }};
    configBluetooth();
    comprobarEstadoBluetooth();
}

@Override
public void onResume() {
    super.onResume();
    Log.d(TAG, "...onResume - try connect...");

    BluetoothDevice device = blueAdapter.getRemoteDevice(MAC);

    try{
        mSocket = crearSocket(device);
    } catch (IOException e) {
        Toast.makeText(getApplicationContext(),"ERROR!! No se ha logrado crear el enchufe! " + e.getMessage(),Toast.LENGTH_LONG).show();
        finish();
    }

    blueAdapter.cancelDiscovery();

    Log.d(TAG, "...Connecting...");
    try{
        mSocket.connect();
        Log.d(TAG,"Connection OK!!");
    } catch (IOException e) {
        try{
            mSocket.close();
        } catch (IOException e1) {
            Toast.makeText(getApplicationContext(),"Error fatal en el metodo onResume. Incapaz de cerrar conexion: " + e1.getMessage(),Toast.LENGTH_LONG).show();
            finish();
        }
    }
    mConnectedThread = new ConnectedThread(mSocket);
    mConnectedThread.start();
}

@Override
public void onPause() {
    super.onPause();
    Log.d(TAG, "...In onPause()...");
    try {
        mSocket.close();
    } catch (IOException e) {
        Toast.makeText(getApplicationContext(),"Error fatal en el metodo onPause. Incapaz de cerrar conexion: " + e.getMessage(),Toast.LENGTH_LONG).show();
    }
}

private void enable() throws IOException {
        boton.setText(getString(R.string.finalizar));
        mensaje.setText(getString(R.string.mensajeActivo));
        frame.setVisibility(View.INVISIBLE);
        imagen.setVisibility(View.VISIBLE);
        mensaje2();
        boton.setText(getString(R.string.iniciar));
        mensaje.setText(getString(R.string.pontelos));
        frame.setVisibility(View.VISIBLE);
        imagen.setVisibility(View.INVISIBLE);
        mensaje1();

}

private void mensajeInicio(){talk.speak(getString(R.string.app_name) + getString(R.string.textApp) + getString(R.string.pontelos),TextToSpeech.QUEUE_FLUSH,null);}
private void mensaje1(){talk.speak(getString(R.string.pontelos),TextToSpeech.QUEUE_FLUSH,null);}
private void mensaje2(){talk.speak(getString(R.string.mensajeActivo),TextToSpeech.QUEUE_FLUSH,null);}

private void configBluetooth(){
    Toast.makeText(getApplicationContext(),"Metodo llamado",Toast.LENGTH_LONG).show();
    blueAdapter = BluetoothAdapter.getDefaultAdapter();
    if(blueAdapter != null){
        Set<BluetoothDevice> pairedDevices = blueAdapter.getBondedDevices();
        if(pairedDevices.size() > 0){
            for(BluetoothDevice device: pairedDevices){
                if(device.getName().equals("HC-06")) {
                    mDevice = device;
                    Toast.makeText(getApplicationContext(), "Nombre del dispositivo: " + mDevice.getName() +
                            "\nDireccion MAC: " + mDevice.getAddress() + ".", Toast.LENGTH_LONG).show();
                }
            }
        }
    }
}

private void comprobarEstadoBluetooth(){
    if(blueAdapter == null){
        Toast.makeText(getApplicationContext(),"ERROR!!! No hay soporte Bluetooth!",Toast.LENGTH_LONG).show();
        finish();
    }else{
        if(blueAdapter.isEnabled()){
            Toast.makeText(getApplicationContext(),"Bluetooth encendido. . .",Toast.LENGTH_LONG).show();
        }else{
            Intent activarBTH = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
            startActivityForResult(activarBTH, 1);
        }
    }
}

private BluetoothSocket crearSocket(BluetoothDevice device) throws IOException {
    if(Build.VERSION.SDK_INT >= 15){
        try{
            final Method m = device.getClass().getMethod("createInsecureRfcommSocketToServiceRecord", new Class[] { UUID.class });
            return (BluetoothSocket) m.invoke(device, uuid);
        } catch (NoSuchMethodException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        }
    }
    return device.createRfcommSocketToServiceRecord(uuid);
}

private class ConnectedThread extends Thread {
    private final InputStream mInStream;
    private final OutputStream mOutStream;

    public ConnectedThread(BluetoothSocket socket) {
        InputStream tmpIn = null;
        OutputStream tmpOut = null;

        // Get the input and output streams, using temp objects because
        // member streams are final
        try {
            tmpIn = socket.getInputStream();
            tmpOut = socket.getOutputStream();
        } catch (IOException e) { }

        mInStream = tmpIn;
        mOutStream = tmpOut;
    }

    public void run() {
        byte[] buffer = new byte[256];  // buffer store for the stream
        int bytes; // bytes returned from read()

        // Keep listening to the InputStream until an exception occurs
        while (true) {
            try {
                // Read from the InputStream
                bytes = mInStream.read(buffer);        // Get number of bytes and message in "buffer"
                handler.obtainMessage(MENSAJE_RECIBIDO, bytes, -1, buffer).sendToTarget();     // Send to message queue Handler
                handler.handleMessage(new Message());
            } catch (IOException e) {
                break;
            }
        }
    }

    /* Call this from the main activity to send data to the remote device */
    public void write(String message) {
        Log.d(TAG, "...Data to send: " + message + "...");
        byte[] msgBuffer = message.getBytes();
        try {
            mOutStream.write(msgBuffer);
        } catch (IOException e) {
            Log.d(TAG, "...Error data send: " + e.getMessage() + "...");
        }
    }
}
}

I notice the following behaviors:

• The application does not crash when it is executed.
• When I start the application, the bluetooth module of the Arduino flashes differently. (I guess it's because my app connectswith the board).
• Inside the Log Cat, it can be seen that the connection has been made correctly. . .

What could be missing here to print the data received from the Arduino? I do not know if it's me, or the handler method never runs. (public void handleMessage (Message msg))

Also note that in the serial monitor of the Arduino, the value that I command when pressing the button of the application is never printed...

UPDATE

Investigating on the internet about the module of my Bluetooth (HC-06) I found that;

• If the light of the module is constantly flashing, it is not paired with the phone.
• If the module light stays on, then it is already connected.

My concern is that when I open my application, to blink constantly, it blinks much slower. . . Could it be that I've never been able to connect?

Answer 1

I don't think your code is correct:

void loop () {
 if (blueTooth.available())
    Serial.write(blueTooth.read());
  if (blueTooth.available())         <---- 
    blueTooth.write(Serial.read());
}

Shouldn't you be monitoring Serial.available on this line?

Answer 2

I could solve it already !!!! It turns out that the bluetooth module was badly connected to the arduino !!!! I can already receive data! thank you very much for your comments, especially chrisl, for your suggestion to use the bluetooth serial monitor app! :)

I had connected the VCC to 5V ... that was what was bothering me, I read on the web that if you have it in 5V, as a self defense, the RX pin is completely blocked. The VCC must be connected to 3.3V.

EDIT: I forgot something very important! had to change the baud of bluetooth to 9600 like Serial! this part was very important too.