Bluetooth Communication between Arduino Nano and Android

This is a Tutorial which teaches how to communicate between Android App and Arduino Nano

1:Connection

2:Arduino code

3:Android Code

Connection

Arduino Code

char c;
void setup() {
 Serial.begin(9600);
}
void loop() {
while (!Serial.available() ) ;//wait until serial is available
 c = Serial.read(); 
 Serial.print(c);
}

Android Code

define a Bluetooth Class in Android Studio which

— Creates a Bluetooth Socket

— Sends data Through the Socket

Two things are needed to make a connection MAC address, of HC05 .
Service ID or UUID. where UUID = 00001101–0000–1000–8000–00805F9B34FB

NOTE change the MAC address in the below code to the MAC address of HC05

import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.bluetooth.BluetoothSocket;
import android.util.Log;
import android.view.View;
import android.widget.TextView;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.util.UUID;
public class BluetoothClass {
    private   BluetoothAdapter mbluetoothAdapter;
    private   BluetoothSocket mbtSocket = null;
    private   DataOutputStream moutStream = null;
    private   DataInputStream minputStream = null;
    //Replace the MAC address of HC05
    private  static String maddress = "00:00:00:00:00:00";
    private   static final String TAG = "SocketBlueTooth";
    private  static final int REQUEST_ENABLE_BT = 1;
    private  static final UUID MY_UUID = UUID.fromString("00001101-0000-1000-8000-00805F9B34FB");
    //Constructor
    public BluetoothClass(BluetoothAdapter bluetoothAdapter) {
        mbluetoothAdapter = bluetoothAdapter;
    }
//Checking for the Bluetooth Adaptor and enabling it if not enabled
    public void checkBTState(){
        // Check for Bluetooth support and then check to make sure it is turned on
        Log.d(TAG, "...Checking  Bluetooth  Adaptor...");
        // if the Device  doesn't support Bluetooth and will return null
        if(mbluetoothAdapter==null) {
            Log.d(TAG,"Fatal Error Bluetooth Not supported. Aborting.");
        } else {
            //if enabled else enable the bluetooth 
            if (mbluetoothAdapter.isEnabled()) {
                Log.d(TAG, "...Bluetooth is enabled...");
            } else {
                mbluetoothAdapter.enable();
                Log.d(TAG, "...Bluetooth is enabled...");
            }
        }
    }
//Disconnect at last
    public void disconnect()
    {
    try {
            if(minputStream!= null && moutStream!=null && mbtSocket!=null) {
                minputStream.close();
                moutStream.close();
                mbtSocket.close();
                }
            mbluetoothAdapter.disable();
        } catch (IOException e) {
              e.printStackTrace();
        }
    }
    
    
    //Creating a Socket to establish a connection
    public void createSocket() throws Exception{
    
        // Set up a pointer to the remote node using it's address.
        BluetoothDevice device = mbluetoothAdapter.getRemoteDevice(maddress);
try {
            mbtSocket = device.createRfcommSocketToServiceRecord(MY_UUID);
        } catch (IOException e) {
            Log.d(TAG,"Fatal Error In onResume() and socket create failed: " + e.getMessage() + ".");
        }
// Discovery is resource intensive.  Make sure it isn't going on
        // when you attempt to connect and pass your message.
        mbluetoothAdapter.cancelDiscovery();
        // Establish the connection.  This will block until it connects.
        Log.d(TAG, "...Connecting to Remote...");
try {
            mbtSocket.connect();
            Log.d(TAG, "...Connection established and data link opened...");
        } catch (IOException e) {
            Log.d(TAG,"Fatal Error In onResume() and unable to close socket during connection failure" + e.getMessage() + ".");
        }
        initializeIOStream();
    }
//Initializing the Input and Output Stream
    private void initializeIOStream() {
        try
        {
            minputStream = new DataInputStream(mbtSocket.getInputStream());
            moutStream = new DataOutputStream(mbtSocket.getOutputStream());
        }catch (IOException e){}
    }
    
    //sending data to Arudino
    public void sendData(String message) {
        byte[]  msgBuffer = message.getBytes();
        Log.d(TAG, "...Sending data: " + message + "...");
        try {
            moutStream.write(msgBuffer);
        }catch (IOException e)
        {
            String msg = "In onResume() and an exception occurred during write: " + e.getMessage();
            msg = msg +  ".\n\nCheck that the SPP UUID: " + MY_UUID.toString() + " exists on server.\n\n";
            Log.d(TAG,msg);
        }
    }
}

Once the BluetoothClass is created, we first need to create the object of class and the call createSocket and sendData

for eg:

BlueetoothClass blueetoothClass = new BlueetoothClass(BluetoothAdapter.getDefaultAdapter());
blueetoothClass.createSocket();
blueetoothClass.sendData("Send Data");