Android + Arduino Bluetooth Data Transfer

Question

I can get my Android app to connect via Bluetooth to my Arduino. However no data can be transmitted between them. Below is my setup and code:

HTC Android v2.2, Bluetooth mate gold modem, Arduino Mega (ATmega1280)

Android Java code:

package com.example.BluetoothExample;

import android.app.Activity;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.bluetooth.BluetoothSocket;
import android.content.Intent;
import android.os.Bundle;
import android.os.Handler;
import android.view.View;
import android.widget.TextView;
import android.widget.EditText;  
import android.widget.Button;
import android.widget.Toast;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Set;
import java.util.UUID;

public class BluetoothExampleActivity extends Activity {
  TextView myLabel;
  EditText myTextbox;
  BluetoothAdapter mBluetoothAdapter;
  BluetoothSocket mmSocket;
  BluetoothDevice mmDevice;
  OutputStream mmOutputStream;
  InputStream mmInputStream;
  Thread workerThread;
  byte[] readBuffer;
  int readBufferPosition;
  int counter;
  volatile boolean stopWorker;

  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    Button openButton = (Button)findViewById(R.id.open);
    Button sendButton = (Button)findViewById(R.id.send);
    Button closeButton = (Button)findViewById(R.id.close);
    myLabel = (TextView)findViewById(R.id.label);
    myTextbox = (EditText)findViewById(R.id.entry);

    //Open Button
    openButton.setOnClickListener(new View.OnClickListener() {
      public void onClick(View v) {
        try {
          findBT();
          openBT();
        }
        catch (IOException ex) { }
      }
    });

    //Send Button
    sendButton.setOnClickListener(new View.OnClickListener() {
      public void onClick(View v) {
        try {
          sendData();
        }
        catch (IOException ex) {
            showMessage("SEND FAILED");
        }
      }
    });

    //Close button
    closeButton.setOnClickListener(new View.OnClickListener() {
      public void onClick(View v) {
        try {
          closeBT();
        }
        catch (IOException ex) { }
      }
    });
  }

  void findBT() {
    mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
    if(mBluetoothAdapter == null) {
      myLabel.setText("No bluetooth adapter available");
    }

    if(!mBluetoothAdapter.isEnabled()) {
      Intent enableBluetooth = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
      startActivityForResult(enableBluetooth, 0);
    }

    Set<BluetoothDevice> pairedDevices = mBluetoothAdapter.getBondedDevices();
    if(pairedDevices.size() > 0) {
      for(BluetoothDevice device : pairedDevices) {
        if(device.getName().equals("FireFly-108B")) {
          mmDevice = device;
          break;
        }
      }
    }
    myLabel.setText("Bluetooth Device Found");
  }

  void openBT() throws IOException {
    UUID uuid = UUID.fromString("00001101-0000-1000-8000-00805f9b34fb"); //Standard //SerialPortService ID
    mmSocket = mmDevice.createRfcommSocketToServiceRecord(uuid);    
    mmSocket.connect();
    mmOutputStream = mmSocket.getOutputStream();
    mmInputStream = mmSocket.getInputStream();
    beginListenForData();
    myLabel.setText("Bluetooth Opened");
  }

  void beginListenForData() {
    final Handler handler = new Handler(); 
    final byte delimiter = 10; //This is the ASCII code for a newline character

    stopWorker = false;
    readBufferPosition = 0;
    readBuffer = new byte[1024];
    workerThread = new Thread(new Runnable() {
      public void run() {
         while(!Thread.currentThread().isInterrupted() && !stopWorker) {
          try {
            int bytesAvailable = mmInputStream.available();            
            if(bytesAvailable > 0) {
              byte[] packetBytes = new byte[bytesAvailable];
              mmInputStream.read(packetBytes);
              for(int i=0;i<bytesAvailable;i++) {
                byte b = packetBytes[i];
                if(b == delimiter) {
                  byte[] encodedBytes = new byte[readBufferPosition];
                  System.arraycopy(readBuffer, 0, encodedBytes, 0, encodedBytes.length);
                  final String data = new String(encodedBytes, "US-ASCII");
                  readBufferPosition = 0;

                  handler.post(new Runnable() {
                    public void run() {
                      myLabel.setText(data);
                    }
                  });
                }
                else {
                  readBuffer[readBufferPosition++] = b;
                }
              }
            }
          } 
          catch (IOException ex) {
            stopWorker = true;
          }
         }
      }
    });

    workerThread.start();
  }

  void sendData() throws IOException {
    String msg = myTextbox.getText().toString();
    msg += "\n";
    //mmOutputStream.write(msg.getBytes());
    mmOutputStream.write('A');
    myLabel.setText("Data Sent");
  }

  void closeBT() throws IOException {
    stopWorker = true;
    mmOutputStream.close();
    mmInputStream.close();
    mmSocket.close();
    myLabel.setText("Bluetooth Closed");
  }

  private void showMessage(String theMsg) {
        Toast msg = Toast.makeText(getBaseContext(),
                theMsg, (Toast.LENGTH_LONG)/160);
        msg.show();
    }
}

Arduino Code:

#include <SoftwareSerial.h>

int bluetoothTx = 45;
int bluetoothRx = 47;

SoftwareSerial bluetooth(bluetoothTx, bluetoothRx);

void setup() {
  //pinMode(45, OUTPUT);
  //pinMode(47, INPUT);
  pinMode(53, OUTPUT);
  //Setup usb serial connection to computer
  Serial.begin(9600);

  //Setup Bluetooth serial connection to android
  bluetooth.begin(115200);
  bluetooth.print("$$$");
  delay(100);
  bluetooth.println("U,9600,N");
  bluetooth.begin(9600);
}

void loop() {
  //Read from bluetooth and write to usb serial
  if(bluetooth.available()) {
  char toSend = (char)bluetooth.read();
  Serial.print(toSend);
  flashLED();
  }

  //Read from usb serial to bluetooth
  if(Serial.available()) {
  char toSend = (char)Serial.read();
  bluetooth.print(toSend);
  flashLED();
  }
}

void flashLED() {
  digitalWrite(53, HIGH);
  delay(500);
  digitalWrite(53, LOW);
}

I've tried using 115200 and 9600 for the baud rates, and I've tried setting the bluetooth rx and tx pins as input/output and output/input. The Arduino is receiving serial data from the PC but can't send it to the Android (I can see this because of the flashLED() method).

The Android can't send any data at all to the Arduino. However they are both connected because the green light on the modem turns on and goes off and the red led flashes when I close the connection. The sendData() method doesn't throw an exception because otherwise showMessage("SEND FAILED"); would appear.

I also have this in my manifest .xml

<uses-permission android:name="android.permission.BLUETOOTH" />
<uses-sdk android:minSdkVersion="8" android:targetSdkVersion="8" />

Any help would be greatly appreciated!

Code taken from:

http://bellcode.wordpress.com/2012/01/02/android-and-arduino-bluetooth-communication/

Your code is working fine have a look of the steps: first you send a connection request to external device once signal accepted it will send back accept signal and connection successful but we are not able to get the incoming data periodically.Means after some time of successful connection. So could you tell me how to get periodic incoming data from another external device. Thanks in advance... — ricintech, Dec 3 '12 at 8:45
hey Hi.I have Arduino device and it sends me Modbus RTU data.How can i read that data over bluetooth? I am done with Bluetooth pairing. But when i write "mmInputStream.available()" it's return me '0' value. Please help me as sooon as possible. Thanks in advance. — Lawrence, Aug 30 '13 at 10:45

Backwards_Dave · Answer 1 · 2012-04-29 13:38:05Z

Just solved the problem for anyone else who came across this page.

Seems that my Arduino doesn't like me using digital pins for serial communication, I use TX and RX instead with this code taken from http://jondontdoit.blogspot.com.au/2011/11/bluetooth-mate-tutorial.html, also seems that 9600 is a good baud instead of 115200.

/***********************
 Bluetooth test program
***********************/
//TODO
//TEST THIS PROGRAM WITH ANDROID,
//CHANGE PINS TO RX AND TX THO ON THE ARDUINO!
//int counter = 0;
int incomingByte;

void setup() {
  pinMode(53, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  // see if there's incoming serial data:
  if (Serial.available() > 0) {
    // read the oldest byte in the serial buffer:
    incomingByte = Serial.read();
    // if it's a capital R, reset the counter
    if (incomingByte == 'g') {
      digitalWrite(53, HIGH);
      delay(500);
      digitalWrite(53, LOW);
      delay(500);
      //Serial.println("RESET");
      //counter=0;
    }
  }

  //Serial.println(counter);
  //counter++;

  //delay(250);
}

Barak · Answer 2 · 2012-10-07 02:02:19Z

I was getting the same thing. I went into 'Settings'->'Wireless and Networks'->'Bluetooth Settings' and paired the device. When I went back and re-ran my code, it connected, no exception. I put controls in my UI for displaying the paired devices, I'm going to see if I can code to manage pairing devices from my UI.

Bluetooth Module · Answer 3 · 2012-05-09 13:15:04Z

I think it might be some fault in Bluetooth.. its better to re-install its drivers.. as the code given above looks correct.

Dan · Answer 4 · 2012-05-19 06:54:53Z

I was able to get this to run only after replacing this section:

Set<BluetoothDevice> pairedDevices = BluetoothAdapter.getBondedDevices();
if(pairedDevices.size() > 0)
    {
        for(BluetoothDevice device : pairedDevices)
        {
            if(device.getName().startsWith("FireFly-"))
            {
                mmDevice = device;
                Log.d("ArduinoBT", "findBT found device named " + mmDevice.getName());
                Log.d("ArduinoBT", "device address is " + mmDevice.getAddress());
                break;
            }
        }
    }

with this:

 Set<BluetoothDevice> pairedDevices = mBluetoothAdapter.getBondedDevices();
 mmDevice = mBluetoothAdapter.getRemoteDevice("00:06:66:46:5A:91");
 if (pairedDevices.contains(mmDevice))
    {
        statusText.setText("Bluetooth Device Found, address: " + mmDevice.getAddress() );
        Log.d("ArduinoBT", "BT is paired");
    }

where I entered the address of my Bluetooth device. The original code finds the device and returns the correct address, but mmSocket.connect(); generates an exception "java.io.IOException: Service discovery failed"

Suggestions?

score 0 · Answer 5

For anyone who finds this page, but is stuck using a hardcoded mac address as above, set mac address to NULL, and insert this code into OnResume()

try{
File f = new File(Environment.getExternalStorageDirectory()+"/mac.txt");
FileInputStream fileIS = new FileInputStream(f);
buf = new BufferedReader(new InputStreamReader(fileIS));
String readString = new String(); 
while((readString = buf.readLine())!= null){
address = readString;
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e){
e.printStackTrace();
}

ALSO, don't forget to allow eclipse to include necessary libraries, and place your mac address into mac.txt on the root of the SD Card, then you can simply give users a text file with their mac address while still allowing the app to be downloaded from the market without customizing every instance.

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