How to get connect with closest bluetooth low energy device from android ?

Question

I want to connect with closest ble device. How to get / calculate closest distance from rssi ?

For example, there are 2 ble device in a room. When I walk in that room, my android device will connect with nearest ble device from my position.

I'm using don cordova plugin and javascript . This project run in android device.

Answer 1

You can use Android Beacon library: https://altbeacon.github.io/android-beacon-library/

It gives readings for distance (which are not exact), but you can use them to detect which beacon is closer.

An example:

public class RangingActivity extends Activity implements BeaconConsumer {
    protected static final String TAG = "RangingActivity";
    private BeaconManager beaconManager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_ranging);
        beaconManager = BeaconManager.getInstanceForApplication(this);
        beaconManager.bind(this);
    }
    @Override 
    protected void onDestroy() {
        super.onDestroy();
        beaconManager.unbind(this);
    }
    @Override
    public void onBeaconServiceConnect() {
        beaconManager.addRangeNotifier(new RangeNotifier() {
            @Override 
            public void didRangeBeaconsInRegion(Collection<Beacon> beacons, Region region) {
                if (beacons.size() > 0) {
                    Log.i(TAG, "The first beacon I see is about "+beacons.iterator().next().getDistance()+" meters away.");        
                }
            }
        });

        try {
            beaconManager.startRangingBeaconsInRegion(new Region("myRangingUniqueId", null, null, null));
        } catch (RemoteException e) {    }
    }
}

Otherwise, you can read the RSSI for the devices, and average them out over a period of time, and take out the outliers. The closer one would be the greater one (in magnitude, more positive).