Android Bluetooth to control LED brightness on Arduino Due + HC-06

Previous exercise "Android example to communicate with Bluetooth device, HC-06 Bluetooth Module" show how to send string. Here we implement our command format, such that we can use SeekBar on Android to control brightness of the Arduino Due on-board LED (pin 13), via Bluetooth to HC-06 Bluetooth Module.

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Android Side:

com.example.androidbtcontrol.MainActivity.java

/*
Android Example to connect to and communicate with Bluetooth
In this exercise, the target is a Arduino Due + HC-06 (Bluetooth Module)

 */
package com.example.androidbtcontrol;

import android.app.Activity;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.bluetooth.BluetoothSocket;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.LinearLayout;
import android.widget.ListView;
import android.widget.ProgressBar;
import android.widget.SeekBar;
import android.widget.TextView;
import android.widget.Toast;

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


public class MainActivity extends ActionBarActivity {

    private static final int REQUEST_ENABLE_BT = 1;

    BluetoothAdapter bluetoothAdapter;

    ArrayList<BluetoothDevice> pairedDeviceArrayList;

    TextView textInfo, textStatus;
    ListView listViewPairedDevice;
    LinearLayout inputPane;

    SeekBar barAnalogOut;

    ArrayAdapter<BluetoothDevice> pairedDeviceAdapter;
    private UUID myUUID;
    private final String UUID_STRING_WELL_KNOWN_SPP =
        "00001101-0000-1000-8000-00805F9B34FB";

    ThreadConnectBTdevice myThreadConnectBTdevice;
    ThreadConnected myThreadConnected;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        textInfo = (TextView)findViewById(R.id.info);
        textStatus = (TextView)findViewById(R.id.status);
        listViewPairedDevice = (ListView)findViewById(R.id.pairedlist);

        inputPane = (LinearLayout)findViewById(R.id.inputpane);

        if (!getPackageManager().hasSystemFeature(PackageManager.FEATURE_BLUETOOTH)){
            Toast.makeText(this,
                    "FEATURE_BLUETOOTH NOT support",
                    Toast.LENGTH_LONG).show();
            finish();
            return;
        }

        //using the well-known SPP UUID
        myUUID = UUID.fromString(UUID_STRING_WELL_KNOWN_SPP);

        bluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
        if (bluetoothAdapter == null) {
            Toast.makeText(this,
                    "Bluetooth is not supported on this hardware platform",
                    Toast.LENGTH_LONG).show();
            finish();
            return;
        }

        String stInfo = bluetoothAdapter.getName() + "\n" +
                bluetoothAdapter.getAddress();
        textInfo.setText(stInfo);

        barAnalogOut = (SeekBar)findViewById(R.id.analogOut);
        barAnalogOut.setOnSeekBarChangeListener(OnAnalogOutChangeListener);

    }

    SeekBar.OnSeekBarChangeListener OnAnalogOutChangeListener =
            new SeekBar.OnSeekBarChangeListener(){
                @Override
                public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
                    //will generate too much data sent!
                    //SendAnalogOut(progress);
                }

                @Override
                public void onStartTrackingTouch(SeekBar seekBar) {

                }

                @Override
                public void onStopTrackingTouch(SeekBar seekBar) {
                    SendAnalogOut(seekBar.getProgress());
                }
            };

    private final byte SYNC_BYTE = (byte) 0xAA;
    private final byte LENGTH_ANALOG = (byte) 3;
    private final byte CMD_ANALOG = (byte) 1;

    private void SendAnalogOut(int val){
        byte[] bytesToSend = {SYNC_BYTE, LENGTH_ANALOG, CMD_ANALOG, (byte) val};
        myThreadConnected.write(bytesToSend);
    }

    @Override
    protected void onStart() {
        super.onStart();

        //Turn ON BlueTooth if it is OFF
        if (!bluetoothAdapter.isEnabled()) {
            Intent enableIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
            startActivityForResult(enableIntent, REQUEST_ENABLE_BT);
        }

        setup();
    }

    private void setup() {
        Set<BluetoothDevice> pairedDevices = bluetoothAdapter.getBondedDevices();
        if (pairedDevices.size() > 0) {
            pairedDeviceArrayList = new ArrayList<BluetoothDevice>();

            for (BluetoothDevice device : pairedDevices) {
                pairedDeviceArrayList.add(device);
            }

            pairedDeviceAdapter = new ArrayAdapter<BluetoothDevice>(this,
                    android.R.layout.simple_list_item_1, pairedDeviceArrayList);
            listViewPairedDevice.setAdapter(pairedDeviceAdapter);

            listViewPairedDevice.setOnItemClickListener(new AdapterView.OnItemClickListener() {

                @Override
                public void onItemClick(AdapterView<?> parent, View view,
                                        int position, long id) {
                    BluetoothDevice device =
                            (BluetoothDevice) parent.getItemAtPosition(position);
                    Toast.makeText(MainActivity.this,
                            "Name: " + device.getName() + "\n"
                                    + "Address: " + device.getAddress() + "\n"
                                    + "BondState: " + device.getBondState() + "\n"
                                    + "BluetoothClass: " + device.getBluetoothClass() + "\n"
                                    + "Class: " + device.getClass(),
                            Toast.LENGTH_LONG).show();

                    textStatus.setText("start ThreadConnectBTdevice");
                    myThreadConnectBTdevice = new ThreadConnectBTdevice(device);
                    myThreadConnectBTdevice.start();
                }
            });
        }
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();

        if(myThreadConnectBTdevice!=null){
            myThreadConnectBTdevice.cancel();
        }
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        if(requestCode==REQUEST_ENABLE_BT){
            if(resultCode == Activity.RESULT_OK){
                setup();
            }else{
                Toast.makeText(this,
                        "BlueTooth NOT enabled",
                        Toast.LENGTH_SHORT).show();
                finish();
            }
        }
    }

    //Called in ThreadConnectBTdevice once connect successed
    //to start ThreadConnected
    private void startThreadConnected(BluetoothSocket socket){

        myThreadConnected = new ThreadConnected(socket);
        myThreadConnected.start();
    }

    /*
    ThreadConnectBTdevice:
    Background Thread to handle BlueTooth connecting
    */
    private class ThreadConnectBTdevice extends Thread {

        private BluetoothSocket bluetoothSocket = null;
        private final BluetoothDevice bluetoothDevice;


        private ThreadConnectBTdevice(BluetoothDevice device) {
            bluetoothDevice = device;

            try {
                bluetoothSocket = device.createRfcommSocketToServiceRecord(myUUID);
                textStatus.setText("bluetoothSocket: \n" + bluetoothSocket);
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }

        @Override
        public void run() {
            boolean success = false;
            try {
                bluetoothSocket.connect();
                success = true;
            } catch (IOException e) {
                e.printStackTrace();

                final String eMessage = e.getMessage();
                runOnUiThread(new Runnable() {

                    @Override
                    public void run() {
                        textStatus.setText("something wrong bluetoothSocket.connect(): \n" + eMessage);
                    }
                });

                try {
                    bluetoothSocket.close();
                } catch (IOException e1) {
                    // TODO Auto-generated catch block
                    e1.printStackTrace();
                }
            }

            if(success){
                //connect successful
                final String msgconnected = "connect successful:\n"
                        + "BluetoothSocket: " + bluetoothSocket + "\n"
                        + "BluetoothDevice: " + bluetoothDevice;

                runOnUiThread(new Runnable(){

                    @Override
                    public void run() {
                        textStatus.setText(msgconnected);

                        listViewPairedDevice.setVisibility(View.GONE);
                        inputPane.setVisibility(View.VISIBLE);
                    }});

                startThreadConnected(bluetoothSocket);
            }else{
                //fail
            }
        }

        public void cancel() {

            Toast.makeText(getApplicationContext(),
                    "close bluetoothSocket",
                    Toast.LENGTH_LONG).show();

            try {
                bluetoothSocket.close();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

        }

    }

    /*
    ThreadConnected:
    Background Thread to handle Bluetooth data communication
    after connected
     */
    private class ThreadConnected extends Thread {
        private final BluetoothSocket connectedBluetoothSocket;
        private final InputStream connectedInputStream;
        private final OutputStream connectedOutputStream;

        public ThreadConnected(BluetoothSocket socket) {
            connectedBluetoothSocket = socket;
            InputStream in = null;
            OutputStream out = null;

            try {
                in = socket.getInputStream();
                out = socket.getOutputStream();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

            connectedInputStream = in;
            connectedOutputStream = out;
        }

        @Override
        public void run() {
            byte[] buffer = new byte[1024];
            int bytes;

            while (true) {
                try {
                    bytes = connectedInputStream.read(buffer);
                    String strReceived = new String(buffer, 0, bytes);
                    final String msgReceived = String.valueOf(bytes) +
                            " bytes received:\n"
                            + strReceived;

                    runOnUiThread(new Runnable() {

                        @Override
                        public void run() {
                            textStatus.setText(msgReceived);
                        }});

                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();

                    final String msgConnectionLost = "Connection lost:\n"
                            + e.getMessage();
                    runOnUiThread(new Runnable(){

                        @Override
                        public void run() {
                            textStatus.setText(msgConnectionLost);
                        }});
                }
            }
        }

        public void write(byte[] buffer) {
            try {
                connectedOutputStream.write(buffer);
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }

        public void cancel() {
            try {
                connectedBluetoothSocket.close();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
    }

}

layout/activity_main.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:orientation="vertical"
    tools:context=".MainActivity">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:autoLink="web"
        android:text="http://android-er.blogspot.com/"
        android:textStyle="bold" />

    <TextView
        android:id="@+id/info"
        android:textStyle="bold|italic"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>
    <TextView
        android:id="@+id/status"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>

    <ListView
        android:id="@+id/pairedlist"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>

    <LinearLayout
        android:id="@+id/inputpane"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical"
        android:visibility="gone">

        <SeekBar
            android:id="@+id/analogOut"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:max="99"
            android:progress="0"/>

    </LinearLayout>

</LinearLayout>

uses-permission of "android.permission.BLUETOOTH" is needed in AndroidManifest.xml.

Download the files (Android Studio Format).

---

Arduino side:

Connection between Arduino and HC-06, refer to "Connect Arduino Due with HC-06 (Bluetooth Module)".

DueHC06_AT.ino

/*
Arduino Due + HC-06 (Bluetooth) - 
receive command to control LED (pin 13) brightness

Serial (Tx/Rx) communicate to PC via USB
Serial3 (Tx3/Rx3) connect to HC-06
HC-06 Rx - Due Tx3
HC-06 Tx - Due Rx3
HC-06 GND - Due GND
HC-06 VCC - Due 3.3V

*/
#define HC06 Serial3

int SYNC_BYTE = 0xAA;
int CMD_ANALOG = 1;

int rxState;
int rxLength;
int rxCmd;
const int rxState_0_idle = 0;
const int rxState_1_sync = 1;  //SYNC_BYTE received
const int rxState_2_cmd = 2;   //length received, waiting CMD
const int rxState_3_data = 3;  //CMD received, receiving data

int LED = 13;

void setup()
{
  pinMode(LED, OUTPUT);
  delay(1000);
  Serial.begin(9600);
  HC06.begin(9600);
  
  Serial.write("\nTest Start\n");
  rxState = rxState_0_idle;
}

void loop()
{
  while(HC06.available())
  {
    char rxData = (int)HC06.read();

    switch(rxState){
      case rxState_0_idle:
          if(rxData == SYNC_BYTE){
            rxState = rxState_1_sync;
            Serial.println("SYNC_BYTE received");
          }
          break;
      case rxState_1_sync:
          rxLength = rxData;
          Serial.println("Length: " + String(rxLength));
          rxLength--;
          rxState = rxState_2_cmd;
          
          break;

      case rxState_2_cmd:
          rxCmd = rxData;
          Serial.println("CMD: " + String(rxCmd));
          
          rxLength--;
          rxState = rxState_3_data;
          break;
          
      case rxState_3_data:
          Serial.println("data: " + String(rxData));
          //we have one command only
          if(rxCmd==CMD_ANALOG){
            int brightness = map(rxData, 0, 99, 0, 255);
            analogWrite(LED, brightness);
            Serial.println("brightness: " + String(brightness));
            HC06.println("brightness: " + String(brightness));
          }
        
          rxLength--;
          if(rxLength==0){
            rxState = rxState_0_idle;
          }

          break;
          
      default:
          rxState = rxState_0_idle;
    };
    
  }
}

You can also monitor the state on PC using Serial Monitor.