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Sensors

Overview

The SDK handles the glasses sensors via the IEvsSensorsService interface (received from the Evs.instance().sensors() method).

The following glasses sensors exists, and are handled by the SDK:

Sensor Description
Touch Touch pad on the right glasses temple arm. The SDK sends touch gestures when occurred
Proximity Used for detecting if the glasses are off\on the face. The SDK sends on\off trigger when relevant
Ambient Used for measuring daylight. The SDK sends the measured information for the application to act. Also it is used by the auto brightness mechanism
Gyroscope For measuring or maintaining orientation and angular velocity
Magnetometer Measures changes in the Earth's magnetic field
Accelerometer Measures acceleration

The SDK enables to disable\enable each sensor (except the proximity) and to consume the sensor data.

All sensors, except proximity, are disabled by default when the glasses are turned on.

Touch

The touch sensor is located on the right glasses temple.

Enabling the touch is done via IEvsSensorsService.enableTouch

The touch events can be received using the IEvsGlassesStateService.registerGlassesEvents or by overriding the Screen.onTouch.

When enabled following discrete touch events are available:

Touch Gesture Description
backward backward swipe
forward forward swipe
tap tapping the touch pad
longTap long pressing the touch pad

Proximity

The proximity sensor enable to detect if the glasses are on of off the face.

The proximity events can be received using the IEvsSensorsService.registerSensorsEvents.

The following proximity events are available:

Touch Gesture Description
offFace Indicates the glasses are off face
onFace Indicates the glasses are on face (proximity sensor is triggered)

Ambient

The ambient sensor is used for measuring daylight.

Enabling the ambient is done via IEvsSensorsService.enableAmbient

The ambient events can be received using the IEvsSensorsService.registerSensorsEvents.

When enabled the IEvsSensorsEvents.onAmbient will be triggered, with the ambient sensor reading in lux.

Inertial Sensors

The glasses inertial sensors includes Gyroscope, Magnetometer and Accelerometer.

Using the SDK, the sensors can be enabled and consumed in the following ways:

Type Description
Base Sensors the sensor x,y,z values are corrected according the the glasses calibration parameters
Fused (Composite) all sensors are fused and the SDK supplies the calibrated Quaternion or YPR information

Coordinate System

The sensors axes are as follows:

Sensors Rate and Rendering Rate

When the inertial sensors are active, they are capturing data at the requested SensorRate.

To optimize the usage of the Bluetooth channel, the collected sensor information is sent from the glasses to the SDK in batches at the requested Screen.ScreenRenderRate interval.

As a result, when you register for one of the sensor event interfaces, the event will be triggered before the rendering cycle, and it may be called multiple times to report each of the collected sensor data within the batch.

The Gyroscope and the Accelerometer using the same underling physical device, hence must be enabled with the same rate.

The Magnetometer rate must be lower then the Gyroscope\Accelerometer rate.

About Sensor Rates

Currently only SensorRate.rate0 and SensorRate.rate1 are operational (the rest are experimental)

See the Sensor Service API Reference for more information

Base Sensors

The calibrated sensors can be received using the IEvsSensorsService.registerInertialSensorsEvents.

In order to receive a calibrated sensors you should:

  1. Register to the required sensor(s) via IEvsSensorsService.registerInertialSensorsEvents
  2. Enable the required sensor(s) via IEvsSensorsService.enableGyro, IEvsSensorsService.enableMagnetometer, IEvsSensorsService.enableAccelerometer

Measurement units

Sensors Units Description
Accelerometer m/s^2 meter/(second^2)
Magnetometer mGauss milli-Gauss
Gyroscope rad/s radians/seconds

Don't forget to disable the sensor and to unregister the events when they are not required.

Fused (Composite)

The fused sensors can be received as Quaternion or YPR.

In order to receive the fused sensors information you should:

  1. Register to the required interface via IEvsSensorsService.registerYprSensorsEvents, IEvsSensorsService.registerQuaternionSensorsEvents
  2. Enable the sensors fusion via IEvsSensorsService.enableSensorsFusion

Enabling the sensors fusion will enable the glasses Gyroscope, Magnetometer, Accelerometer and will start the fusion algorithm process.

Don't forget to disable the sensor fusion and to unregister the events when they are not required.

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