Ambient Light Sensor

Ambient light sensors convert light intensity into a digital signal using a combination of photodiodes and analog-to-digital converters. The light sensor of choice on select boards is the LTR-329ALS device from Lite-On, represented by the AmbientLightLtr329 interface.

import com.mbientlab.metawear.module.AmbientLightLtr329;

final AmbientLightLtr329 alsLtr329 = board.getModule(AmbientLightLtr329.class);

Configuration

The sensor has three configurable parameters, set with the module’s ConfigEditor class:

Parameter	Description
Gain	Controls data range and resolution
Integration Time	Measurement time for each cycle
Measurement Rate	How frequently to update illuminance data

import com.mbientlab.metawear.module.AmbientLightLtr329.*;

// Set the gain to 8x
// Set integration time to 250ms
// Set measurement rate to 50ms
alsLtr329.configure()
        .gain(Gain.LTR329_8X)
        .integrationTime(IntegrationTime.LTR329_TIME_250MS)
        .measurementRate(MeasurementRate.LTR329_RATE_50MS)
        .commit();

Illuminance Data

Illuminance data is categorized as an async data producer; data is interpreted as a float value and is in units of lux (lx).

alsLtr329.illuminance().addRouteAsync(new RouteBuilder() {
    @Override
    public void configure(RouteComponent source) {
        source.stream(new Subscriber() {
            @Override
            public void apply(Data data, Object... env) {
                Log.i("MainActivity", String.format(Locale.US, "illuminance = %.3f lx".
                        data.value(Float.class)));
            }
        });
    }
}).continueWith(new Continuation<Route, Void>() {
    @Override
    public Void then(Task<Route> task) throws Exception {
        alsLtr329.illuminance().start();
        return null;
    }
});