Control an Android device from Arduino

In a previous article we looked at Control an Arduino from your Android device. In this article we will discuss how to Control an Android device from Arduino.

In Android device we will send 2 variables: random number and state state of the button.

Arduino Code

#include 
#include 

// Adb connection.
Connection * connection;
long lastTime;
byte rndNum;    // Random number
int buttonState = 0;  // State of the button
uint16_t tosend;      // Data send to Android
const int buttonPin = 2;  // Button PIN

void setup()
{
  pinMode(buttonPin, INPUT);
  
  // Initialization ADB.  
  ADB::init();

  // Open an ADB stream to the phone's shell. Auto-reconnect. Use any unused port number eg:4568
  connection = ADB::addConnection("tcp:4568", true, NULL);
  
  //Serial.begin(115200);
  randomSeed(analogRead(0));
}

void loop()
{
  if ((millis() - lastTime) > 100)  // Every 100 ms
  {
    rndNum = random(1, 99);    // Random number from 1 to 99
    buttonState = digitalRead(buttonPin);  // State of the button
    
    tosend = (rndNum << 8) | buttonState;  // Make a word from 2 bytes

    Serial.println(tosend,BIN);
    connection->write(2,(uint8_t*)&tosend);  // Send 2 bytes

    lastTime = millis();
  }

  // Poll the ADB subsystem.
  ADB::poll();
}

Android code

For our Activity we need 2 elements: TextView and Switch.

Source code of MainActivity:

package com.example.arduino53;

import java.io.IOException;

import org.microbridge.server.Server;
import org.microbridge.server.AbstractServerListener;

import android.os.AsyncTask;
import android.os.Bundle;
import android.app.Activity;
import android.util.Log;
import android.widget.Switch;
import android.widget.TextView;

public class MainActivity extends Activity {
    
    private int Ard_data1 = 0;
    private int Ard_data2 = 0;
    public final String APP_NAME = "arduino53";
    
    Server server = null;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        // Create TCP server (MicroBridge LightWeight)
      try
      {
          server = new Server(4568); //Port
          server.start();            
      } catch (IOException e)
      {
          Log.e(APP_NAME, "Unable to start TCP server", e);
          System.exit(-1);
      }
          
        server.addListener(new AbstractServerListener() {

            @Override
            public void onReceive(org.microbridge.server.Client client, byte[] data)
            {
                Log.d(APP_NAME, "data0:"+data[0]+"; data1:"+data[1]);
                if (data.length<2) Log.e(APP_NAME, "The data less than 2 bytes:"+data.length);

                Ard_data1 = data[0];
                Ard_data2 = data[1];
                        
                //Any update to UI can not be carried out in a non UI thread like the one used
                //for Server. Hence runOnUIThread is used.
                runOnUiThread(new Runnable() {
                    //@Override
                    public void run() {
                        new UpdateData().execute(Ard_data1,Ard_data2);
                    }
                });
            }
        });     
    }
    
    @Override
    protected void onDestroy (){
     super.onDestroy();
     server.stop();
    }
    
    class UpdateData extends AsyncTask {
        // Called to initiate the background activity
        @Override
        protected Integer[] doInBackground(Integer... ArdState) {
            return (ArdState);  //Return to onPostExecute()
        }
        
        @Override
        protected void onProgressUpdate(Integer... values) {
            super.onProgressUpdate(values);
            // Not used in this case
        }
        
        @Override
        protected void onPostExecute(Integer... result) {      	
            //Log.d(APP_NAME, "onPostExecute0:"+result[0]);
            //Log.d(APP_NAME, "onPostExecute1:"+result[1]);
                       
            TextView txt_btn_Arduino = (TextView) findViewById(R.id.textDistance);
            txt_btn_Arduino.setText(String.valueOf(result[1]));    // Print a random number from Arduino to activity
            
            Switch switch1 = (Switch) findViewById(R.id.switch1);
            
            if(result[0] == 1){
                switch1.setChecked(true);		// Toggle state switch
            }
            else switch1.setChecked(false);
        }
    }
}

In this code uses method onReceive() which is called whenever data comes from Arduino. To update UI elements on Activity we use a class AsyncTask.

Video:

Download source code for Arduino, Android and Libraries

Author: Koltykov A.V.