Always know your vehicles fuel level state!

What if car manufacturers would provide us applications to view information of our vehicles on our smartwatches?
Wouldn’t it be nice?

Since there are a lot of apps for smartphones, it should be possible to adapt those functionalities to wearable platforms (e.g. Android Wearable).
So I decided to develop such an app.

What I needed:

A smartwatch (Moto360)
An ELM 327 WiFi adapter (to read data directly from a car) – or another OBD-2 adapter
A smartphone (OnePlus One – Android 4.4)
Information about the OBD-2 protocol – Click here to see all standard PIDs

Ahh and don’t forget:

A car

But first let me show you the result:

smartwatch_car_info — Smartwatch with car information

So the scenario is very simple. The smartwatch is connected via BLUETOOTH to the smartphone.
The smartphone is via WiFi (TCP/IP) connected to the ELM 327 WiFi Adapter, to do data requests.
Once data is requested by the phone, the adapter will forward the request to the car and delivers the answer back to the phone, which will transmit the data to the watch.

The only thing you really have to know, is the OBD-2 Protokoll, to send the right requests to your car.
Everything else is just a little bit of coding and designing.

In my case I’ve used the following protocol:

To initialize (MB 2013 and newer):

AT Z

AT L0

AT E1

AT H1

AT SP 0

01 00

AT DP

To read specific data e.g. fuel level:

01 2F

Cheers
Lars

** IMPORTANT REMARK (2017) : THE CODE IS JUST A QUICK & DIRTY PROTOTYPE SNIPPET EXAMPLE AND DOES NOT MATCH CURRENT DEVELOPMENT GUIDELINES! **

Btw: the sourcecode is added below.

Smartwatch application
- 1.1 Design / Markup
- 1.2 Manifest
- 1.3 WearableListenerService
- 1.4 Communication
- 1.5 Data storage
Smartphone application
- 2.1 Manifest
- 2.2 Communication ELM 327
- 2.3 Communication Smartwatch

+ 1. Smartwatch (Sourcecode)

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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:background="#000000" tools:context=".MainActivity" tools:deviceIds="wear_round">

    <ProgressBar
        android:id="@+id/pbarEmpty"
        style="?android:attr/progressBarStyleHorizontal"
        android:layout_width="match_parent"
        android:layout_height="273dp"
        android:layout_alignParentStart="true"
        android:indeterminate="false"
        android:max="100"
        android:progress="99"
        android:progressDrawable="@drawable/circular_progress_bar"
        android:rotation="90"/>

    <ProgressBar
        android:id="@+id/pbarState"
        style="?android:attr/progressBarStyleHorizontal"
        android:layout_width="match_parent"
        android:layout_height="273dp"
        android:layout_alignParentStart="true"
        android:indeterminate="false"
        android:max="100"
        android:progress="1"
        android:progressDrawable="@drawable/circular_progress_bar"
        android:rotation="90"  />


    <TextView
        android:id="@+id/txtFuelText"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true" android:alpha="1"
        android:layout_marginTop="48dp"
        android:text="@string/fuel_text"
        android:textAppearance="?android:attr/textAppearanceMedium"
        android:textColor="#ffffff"
        android:textSize="23dp"
        android:fontFamily="sans-serif-light"
        />

    <ImageView
        android:id="@+id/imgFuelIcon"
        android:layout_width="65dp"
        android:layout_height="75dp"
        android:layout_below="@+id/txtFuelText"
        android:background="@drawable/fuel_icon"
        android:layout_marginTop="10dp"
        android:layout_centerHorizontal="true"
        android:alpha="0.9"
        />

    <TextView
        android:id="@+id/txtFuelState"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/imgFuelIcon"
        android:layout_centerHorizontal="true"
        android:text="@string/fuel_initial_value"
        android:textAppearance="?android:attr/textAppearanceMedium"
        android:textColor="#09aae0"
        android:textSize="25dp"
        android:layout_marginTop="7dp"
        android:fontFamily="sans-serif-light"
        />
</RelativeLayout>

<?xml version="1.0" encoding="utf-8"?>

<RelativeLayout 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:background="#000000" tools:context=".MainActivity" tools:deviceIds="wear_round">

<ProgressBar

android:id="@+id/pbarEmpty"

style="?android:attr/progressBarStyleHorizontal"

android:layout_width="match_parent"

android:layout_height="273dp"

android:layout_alignParentStart="true"

android:indeterminate="false"

android:max="100"

android:progress="99"

android:progressDrawable="@drawable/circular_progress_bar"

android:rotation="90"/>

<ProgressBar

android:id="@+id/pbarState"

style="?android:attr/progressBarStyleHorizontal"

android:layout_width="match_parent"

android:layout_height="273dp"

android:layout_alignParentStart="true"

android:indeterminate="false"

android:max="100"

android:progress="1"

android:progressDrawable="@drawable/circular_progress_bar"

android:rotation="90" />

<TextView

android:id="@+id/txtFuelText"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_alignParentTop="true"

android:layout_centerHorizontal="true" android:alpha="1"

android:layout_marginTop="48dp"

android:text="@string/fuel_text"

android:textAppearance="?android:attr/textAppearanceMedium"

android:textColor="#ffffff"

android:textSize="23dp"

android:fontFamily="sans-serif-light"

<ImageView

android:id="@+id/imgFuelIcon"

android:layout_width="65dp"

android:layout_height="75dp"

android:layout_below="@+id/txtFuelText"

android:background="@drawable/fuel_icon"

android:layout_marginTop="10dp"

android:layout_centerHorizontal="true"

android:alpha="0.9"

<TextView

android:id="@+id/txtFuelState"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_below="@+id/imgFuelIcon"

android:layout_centerHorizontal="true"

android:text="@string/fuel_initial_value"

android:textAppearance="?android:attr/textAppearanceMedium"

android:textColor="#09aae0"

android:textSize="25dp"

android:layout_marginTop="7dp"

android:fontFamily="sans-serif-light"

</RelativeLayout>

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.larsfeicho.car_info" >
    <uses-feature android:name="android.hardware.type.watch" />

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:theme="@android:style/Theme.DeviceDefault" >

        <meta-data android:name="com.google.android.gms.version" android:value="@integer/google_play_services_version" />

        <activity
            android:name=".MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

        <service android:name=".WearMessageListenerService">
            <intent-filter>
                <action android:name="com.google.android.gms.wearable.BIND_LISTENER" />
            </intent-filter>
        </service>
    </application>
</manifest>

<?xml version="1.0" encoding="utf-8"?>

<manifest xmlns:android="http://schemas.android.com/apk/res/android"

package="com.larsfeicho.car_info" >

<uses-feature android:name="android.hardware.type.watch" />

<application

android:allowBackup="true"

android:icon="@mipmap/ic_launcher"

android:label="@string/app_name"

android:theme="@android:style/Theme.DeviceDefault" >

<activity

android:name=".MainActivity"

android:label="@string/app_name" >

<intent-filter>

</intent-filter>

</activity>

<intent-filter>

</intent-filter>

</service>

</application>

</manifest>

package com.larsfeicho.car_info;

import android.content.Intent;

import com.google.android.gms.wearable.MessageEvent;
import com.google.android.gms.wearable.WearableListenerService;

/**
 * Created by LFE on 28.03.2015.
 */
public class WearMessageListenerService extends WearableListenerService {
    private static final String START_ACTIVITY = "/start_activity";

    @Override
    public void onMessageReceived(MessageEvent messageEvent) {
        if( messageEvent.getPath().equalsIgnoreCase( START_ACTIVITY ) ) {
            Intent intent = new Intent( this, MainActivity.class );
            intent.addFlags( Intent.FLAG_ACTIVITY_NEW_TASK );
            startActivity( intent );
        } else {
            super.onMessageReceived(messageEvent);
        }
    }
}

package com.larsfeicho.car_info;

import android.content.Intent;

import com.google.android.gms.wearable.MessageEvent;

import com.google.android.gms.wearable.WearableListenerService;

/**

* Created by LFE on 28.03.2015.

public class WearMessageListenerService extends WearableListenerService {

private static final String START_ACTIVITY = "/start_activity";

@Override

public void onMessageReceived(MessageEvent messageEvent) {

if( messageEvent.getPath().equalsIgnoreCase( START_ACTIVITY ) ) {

Intent intent = new Intent( this, MainActivity.class );

intent.addFlags( Intent.FLAG_ACTIVITY_NEW_TASK );

startActivity( intent );

} else {

super.onMessageReceived(messageEvent);

}

@Override
    public void onMessageReceived( final MessageEvent messageEvent ) {
        runOnUiThread( new Runnable() {
            @Override
            public void run() {
                if( messageEvent.getPath().equalsIgnoreCase( WEAR_MESSAGE_PATH ) ) {

                    try{
                        String data = new String(messageEvent.getData());
                        Log.wtf("Received", data);

                        int fuelLevel = Integer.parseInt(data);
                       
                        ObjectAnimator animation = ObjectAnimator.ofInt(pBarFuel, "progress", fuelLevel);
                        animation.setDuration(1000); // 1 second
                        animation.setInterpolator(new DecelerateInterpolator());
                        animation.start();

                        saveFuelData(data + "%");
                    }catch(Exception e){
                        Log.wtf("Error", e.toString());
                    }
                }
            }
        });
    }

@Override

public void onMessageReceived( final MessageEvent messageEvent ) {

runOnUiThread( new Runnable() {

@Override

public void run() {

if( messageEvent.getPath().equalsIgnoreCase( WEAR_MESSAGE_PATH ) ) {

try{

String data = new String(messageEvent.getData());

Log.wtf("Received", data);

int fuelLevel = Integer.parseInt(data);

ObjectAnimator animation = ObjectAnimator.ofInt(pBarFuel, "progress", fuelLevel);

animation.setDuration(1000); // 1 second

animation.setInterpolator(new DecelerateInterpolator());

animation.start();

saveFuelData(data + "%");

}catch(Exception e){

Log.wtf("Error", e.toString());

}

});

}

private void saveFuelData(String fuelState){
        try{
            SharedPreferences sharedPref = PreferenceManager.getDefaultSharedPreferences(getBaseContext());
            SharedPreferences.Editor editor = sharedPref.edit();
            editor.putString(LEVEL_FUEL_DATA, fuelState);
            editor.commit();
        }catch (Exception e){
            Log.wtf("Error", e.toString());
        }
    }

private void saveFuelData(String fuelState){

try{

SharedPreferences sharedPref = PreferenceManager.getDefaultSharedPreferences(getBaseContext());

SharedPreferences.Editor editor = sharedPref.edit();

editor.putString(LEVEL_FUEL_DATA, fuelState);

editor.commit();

}catch (Exception e){

Log.wtf("Error", e.toString());

}

+ 2. Smartphone (Sourcecode)

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.larsfeicho.car_info" >
    <uses-permission android:name="android.permission.INTERNET" />

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >

        <meta-data android:name="com.google.android.gms.version" android:value="@integer/google_play_services_version" />
        <activity
            android:name=".MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

<?xml version="1.0" encoding="utf-8"?>

<manifest xmlns:android="http://schemas.android.com/apk/res/android"

package="com.larsfeicho.car_info" >

<uses-permission android:name="android.permission.INTERNET" />

<application

android:allowBackup="true"

android:icon="@mipmap/ic_launcher"

android:label="@string/app_name"

android:theme="@style/AppTheme" >

<activity

android:name=".MainActivity"

android:label="@string/app_name" >

<intent-filter>

</intent-filter>

</activity>

</application>

</manifest>

package com.larsfeicho.car_info.TCP;

import android.util.Log;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.InetAddress;
import java.net.Socket;

/**
 * Created by LFE on 28.03.2015.
 */
public class SocketImp {
    public static final String SRV_IP = "192.168.0.10";
    public static final int SRV_PORT = 35000;
    private static final String PROMPT_CONST = ">";
    private static final String CR_CONST = "\n";
    private static final String LF_CONST = "\r";

    private String serverMessage;
    private OnMessageReceived mMsgListener = null;
    private boolean mIsRunning = false;

    private OutputStream mOutStream;
    private InputStream mInStream;

    public SocketImp(OnMessageReceived listener) {
        mMsgListener = listener;
    }

    public void sendMessage(String message){
        if (mOutStream != null) {

            try {
                mOutStream.write(message.getBytes());

            } catch (IOException e) {
                e.printStackTrace();
                Log.wtf("Error", e.toString());
            }
        }
    }

    public void stopSocketClient(){
        mIsRunning = false;
    }

    public void run() {

        mIsRunning = true;

        try {
            InetAddress srvAddr = InetAddress.getByName(SRV_IP);
            Socket sock = new Socket(srvAddr, SRV_PORT);

            try {
                mOutStream =  sock.getOutputStream();
                mInStream = sock.getInputStream();

                byte[] bytes = null;
                boolean toSend = false;

                while (mIsRunning) {

                    while(mInStream.available() > 0){
                        toSend = true;
                        int ready = mInStream.available();
                        bytes = new byte[ready];
                        sock.getInputStream().read(bytes);
                    }

                    if(toSend){
                        String respString =new String(bytes, "UTF-8");

                        respString = respString.replace(CR_CONST, "");
                        respString = respString.replace(LF_CONST, "");
                        respString = respString.replace(PROMPT_CONST, "");

                        mMsgListener.messageReceived(respString);
                        toSend = false;
                    }
                }
            } catch (Exception e) {
                Log.wtf("TCP", "Failed", e);

            } finally {
                sock.close();
            }

        } catch (Exception e) {

            Log.wtf("TCP", "Failed", e);
        }
    }
    public interface OnMessageReceived {
        public void messageReceived(String message);
    }
}

package com.larsfeicho.car_info.TCP;

import android.util.Log;

import java.io.IOException;

import java.io.InputStream;

import java.io.OutputStream;

import java.net.InetAddress;

import java.net.Socket;

/**

* Created by LFE on 28.03.2015.

public class SocketImp {

public static final String SRV_IP = "192.168.0.10";

public static final int SRV_PORT = 35000;

private static final String PROMPT_CONST = ">";

private static final String CR_CONST = "\n";

private static final String LF_CONST = "\r";

private String serverMessage;

private OnMessageReceived mMsgListener = null;

private boolean mIsRunning = false;

private OutputStream mOutStream;

private InputStream mInStream;

public SocketImp(OnMessageReceived listener) {

mMsgListener = listener;

}

public void sendMessage(String message){

if (mOutStream != null) {

try {

mOutStream.write(message.getBytes());

} catch (IOException e) {

e.printStackTrace();

Log.wtf("Error", e.toString());

}

public void stopSocketClient(){

mIsRunning = false;

}

public void run() {

mIsRunning = true;

try {

InetAddress srvAddr = InetAddress.getByName(SRV_IP);

Socket sock = new Socket(srvAddr, SRV_PORT);

try {

mOutStream = sock.getOutputStream();

mInStream = sock.getInputStream();

byte[] bytes = null;

boolean toSend = false;

while (mIsRunning) {

while(mInStream.available() > 0){

toSend = true;

int ready = mInStream.available();

bytes = new byte[ready];

sock.getInputStream().read(bytes);

}

if(toSend){

String respString =new String(bytes, "UTF-8");

respString = respString.replace(CR_CONST, "");

respString = respString.replace(LF_CONST, "");

respString = respString.replace(PROMPT_CONST, "");

mMsgListener.messageReceived(respString);

toSend = false;

}

} catch (Exception e) {

Log.wtf("TCP", "Failed", e);

} finally {

sock.close();

}

} catch (Exception e) {

Log.wtf("TCP", "Failed", e);

}

public interface OnMessageReceived {

public void messageReceived(String message);

}

private void initGoogleApiClient() {
    mApiClient = new GoogleApiClient.Builder( this )
            .addApi( Wearable.API )
            .build();

    mApiClient.connect();
}

protected void onDestroy() {
    super.onDestroy();
    mApiClient.disconnect();
}

private void sendMessage( final String path, final String text ) {
    new Thread( new Runnable() {
        @Override
        public void run() {
            NodeApi.GetConnectedNodesResult nodes = Wearable.NodeApi.getConnectedNodes( mApiClient ).await();
            for(Node node : nodes.getNodes()) {
                MessageApi.SendMessageResult result = Wearable.MessageApi.sendMessage(
                        mApiClient, node.getId(), path, text.getBytes() ).await();
            }
        }
    }).start();
}

private void initGoogleApiClient() {

mApiClient = new GoogleApiClient.Builder( this )

.addApi( Wearable.API )

.build();

mApiClient.connect();

}

protected void onDestroy() {

super.onDestroy();

mApiClient.disconnect();

}

private void sendMessage( final String path, final String text ) {

new Thread( new Runnable() {

@Override

public void run() {

NodeApi.GetConnectedNodesResult nodes = Wearable.NodeApi.getConnectedNodes( mApiClient ).await();

for(Node node : nodes.getNodes()) {

MessageApi.SendMessageResult result = Wearable.MessageApi.sendMessage(

mApiClient, node.getId(), path, text.getBytes() ).await();

}

}).start();

}

Always know your vehicles fuel level state!

+ 1. Smartwatch (Sourcecode)

+ 2. Smartphone (Sourcecode)

Lars D. FeichoPost author

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