Android sensors

List of sensors• Make new app.• In onCreate add

– SensorManager sensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);– List<Sensor> list = sensorManager.getSensorList(Sensor.TYPE_ALL);– for (Sensor s : list) {

• Log.e("SENSORS","name: "+s.getName());

– }

Nexus One Sensors• BMA150 3-axis Accelerometer• AK8973 3-axis Magnetic field sensor• AK8973 Orientation sensor• CM3602 Proximity sensor• CM3602 Light sensor• Linear Acceleration Sensor• Rotation Vector Sensor

Nexus S Sensors• KR3DM 3-axis Accelerometer• AK8973 3-axis Magnetic field sensor• AK8973 Orientation sensor• GP2A Proximity sensor• GP2A Light sensor• Linear Acceleration Sensor• Rotation Vector Sensor• K3G Gyroscope sensor• Gravity Sensor

API also supports• pressure sensor (to help determine altitude)

compass

• New app: Compass• Add member variables– SensorManager sensorManager;– Sensor compassSensor;– MyCompassListener myCompassListener = new

MyCompassListener(); // we need to make this

MyCompassListener

• Make class– class MyCompassListener implements

SensorEventListener {};• Let eclipse add unimplemented functions• In onSensorChanged(SensorEvent event), add– Log.e("compass","x: "+event.values[0]+"y:

"+event.values[1]);

Register our sensor listener• In onCreate, get sensor and register listener

– sensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE); – List<Sensor> list = sensorManager.getSensorList(Sensor.TYPE_ALL);– for (Sensor s : list) {

• Log.e("SENSORS","name: "+s.getName()+" tpye: "+s.getType()); • if (s.getType()==Sensor.TYPE_MAGNETIC_FIELD) {

– Log.e("debuginfo","registering lin accel");– compassSensor = s;– sensorManager.registerListener(myCompassListener, s, sensorManager.SENSOR_DELAY_FASTEST);

• } – }

• Run and see compass values

unregister and reregister• Sensors will keep on creating events, so we must stop the events

when the app is not active• In main activity

– @Override– public void onPause() {

• super.onPause();• sensorManager.unregisterListener(myCompassListener);

– }– @Override – public void onResume() {

• super.onResume();• sensorManager.registerListener(myCompassListener, compassSensor,

sensorManager.SENSOR_DELAY_FASTEST);

– }

Draw compass

• Recall simple drawing on a canvas lecture• In graphical editor, add “view” object. • Save• Go to xml and make the just made entry be of type

edu.udel.eleg454.MyView instead of View– This requires replacing view and /view

• Make new class– MyView that extends view– Add

• public MyView(Context context, AttributeSet attrs) {– super(context, attrs);

• }• public MyView(Context context) {

– super(context);

• }

• In MyView, add member variables– public float x=0;– public float y=1;– float scale;

• In onDraw, add– Paint paint = new Paint();– paint.setDither(true);– paint.setColor(Color.RED);– paint.setStyle(Paint.Style.FILL_AND_STROKE);– paint.setStrokeJoin(Paint.Join.ROUND);– paint.setStrokeCap(Paint.Cap.ROUND);– paint.setStrokeWidth(2);

• Now draw the compass– scale = (float) Math.sqrt(x*x+y*y); // normalize– x = x/scale*50;– y = y/scale*50;– canvas.drawLine(100,100,100+y,100+x, paint);

In Compass (our main activity class)

• In onCreate, get the view– view = (MyView)findViewById(R.id.View01);

• In onSensorChanged(SensorEvent event), add– view.x = event.values[0];– view.y = event.values[1];– view.invalidate(); // forces redraw

• run

More sensors - Proximity

• Make new app (or maybe canalized Compass)• Add member variables

– SensorManager sensorManager;– Sensor sensor;– MySensorListener mySensorListener = new MySensorListener (); // we need to make this

• In onCreate() add,• if (s.getType()==Sensor.TYPE_PROXIMITY) {

– Log.e("debuginfo","registering lin accel");

– compassSensor = s;– sensorManager.registerListener(myCompassListener, s,

sensorManager.SENSOR_DELAY_FASTEST);• }

• Make MySensorListener as we made MyCompassListener • In onSensorChanged add

– if (event.sensor.getType()==Sensor.TYPE_PROXIMITY) {• Log.e("Proximity ","x: "+event.values[0]);

– }

• Run

• Try with light sensor– Sensor.TYPE_LIGHT

Linear Accelerometer• Make a linear accelerometer listener• Register listener• Add member variable

– MyLinearAccelerationListener myLinearAccelerationListener = new MyLinearAccelerationListener();

• Add local class– class MyLinearAccelerationListener implements SensorEventListener { };– Let eclipse add unimplemented methods– Add class member variables

• double[] linear_acceleration = new double[3];• double[] location = new double[3];• double[] velocity = new double[3];• long lastTimeStamp = 0;• double timeDif;

– In onSensorChanged(SensorEvent event) // make sure arg is called event– if (event.sensor.getType()==10) {– if (lastTimeStamp>0) {– // to do: add a jetPlayer-based sounds

• timeDif = ((double)(event.timestamp - lastTimeStamp))/1e9;• velocity[0] = velocity[0] + timeDif*event.values[0];• velocity[1] = velocity[1] + timeDif*event.values[1];• velocity[2] = velocity[2] + timeDif*event.values[2];• location[0] = location[0] + timeDif*velocity[0];• location[1] = location[1] + timeDif*velocity[1];• location[2] = location[2] + timeDif*velocity[2];• locationView.setText("location x: "+((double)((int)(location[0]*10.0)))/10.0+ " y: "+ ((double)((int)

(location[1]*10.0)))/10.0+" z: "+((double)((int)(location[2]*10.0)))/10.0);• velocityView.setText("velocity x: "+((double)((int)(velocity[0]*10.0)))/10.0+ " y: "+ ((double)((int)

(velocity[1]*10.0)))/10.0+" z: "+((double)((int)(velocity[2]*10.0)))/10.0);– }– lastTimeStamp = event.timestamp;– }

accelerometer• Challenge: remove gravity from measurement

– gravity[0] = alpha * gravity[0] + (1 - alpha) * event.values[0];

– gravity[1] = alpha * gravity[1] + (1 - alpha) * event.values[1];– gravity[2] = alpha * gravity[2] + (1 - alpha) * event.values[2];– scale = Math.sqrt(gravity[0]*gravity[0] + gravity[1]*gravity[1] +

gravity[2]*gravity[2])/SensorManager.GRAVITY_EARTH; – gravity[0] = gravity[0]/scale;– gravity[1] = gravity[1]/scale;– gravity[2] = gravity[2]/scale;

• linear_acceleration[0] = event.values[0] - gravity[0];• linear_acceleration[1] = event.values[1] - gravity[1];• linear_acceleration[2] = event.values[2] - gravity[2];• SAME as linear accelerometer

todo

• Rotation sensor or gyroscope– Show opengl image that rotates as phone rotates

• E.g., see navigator

– Allow phone to work as joystick• Gesture recognition– Hidden markov models

• Location tracking– Keep history– Gryoscope (to track gravity)– Statistical signal processing