Intro - A4100 Sample Health App Using PPG Sensor

Background

This document covers the foundational technical details of PPG Sensors utilized in Heart Rate, Breathing Rate, and Blood Oxygen Monitoring on Mason A4100.  This document provides code snippets and navigational data flows and the public GitHub codebase source is shared in the below sections.

PPG - “Photoplethysmography” is a technique that can be applied to various aspects of cardiovascular monitoring, including the detection of blood oxygen saturation, heart rate, etc

The A4100 is not a medical device and should not be used for medical purposes. The A4100 is not intended to diagnose, treat, cure or prevent any medical condition.  This sample Health app using PPG sensor should not be used for medical purposes.  If you are experiencing symptoms of a medical condition or have concerns about your health, you should seek the advice of a medical professional immediately.

Each section is explained in detail in below sections: 

Getting Started - Listening to Sensor

To get the reading use SensorManager Class. Different devices have a variety of sensors that can be accessed via the sensor framework. Possible tasks related to sensors include:

• List available sensors
• Determine sensor capabilities (range, resolution, etc)
• Acquire raw sensor data
• Register sensor event listeners

It's also important to note that this example uses the onResume() and onPause() callback methods to register and unregister the sensor event listener. As a best practice, you should disable sensors you don't need, especially when your activity is paused. This will help reduce battery consumption. 

// Add Uses Feature to AndroidManifest

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

// Declare SensorManage and Sensor variable 

private SensorManager sensorManager;
private Sensor sensor;<br>

// Get sensor manager

sensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);<br>

// Get the default sensor of the specified type

sensor = sensorManager.getDefaultSensor(Sensor.TYPE_HEART_RATE);

//Start Sensor

private void startMeasure() {
   boolean sensorRegistered = sensorManager.registerListener(this, sensor, SensorManager.SENSOR_DELAY_FASTEST, null);
   sensorManager.registerListener(this, sensorManager.getDefaultSensor(Sensor.TYPE_LOW_LATENCY_OFFBODY_DETECT), SensorManager.SENSOR_DELAY_FASTEST);
   Log.d("Sensor Status:", " Sensor registered: " + (sensorRegistered ? "yes" : "no"));
}

//Stop Sensor

// Stop Sensor 
private void stopMeasure() {
   sensorManager.unregisterListener(this);
}<br>

//Register and Unregister Sensor

@Override
protected void onResume() {
   super.onResume();
   startMeasure();
}

@Override
protected void onPause() {
   super.onPause();
   stopMeasure();
}

Data collection for new sensor event 

For SensorManager to get notified of new sensor data, one should utilize the public interface SensorEventListener. This has two callback methods: 

Please Note: onAccuracyChanged() is called when the accuracy of the registered sensor has changed. Unlike onSensorChanged(), this is only called when this accuracy value is changed.

Enable Health in App Launcher

To initiate a measurement, wear the watch on your wrist and go to the Launcher Screen. There we can see the Health Option on the Launcher app list.

// To enable Health in launcher list  Below is the code snippet in AndroidManifest.xml

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

Upon clicking the health item from the list it will take you to the submenu in the health category.

Next Up:

Heart Rate - A4100 Sample Health App PPG Sensor