Qt Sensors C++ Overview

Explains how to use the Qt Sensors C++ API.

Sensor Types

On a device there can be many types of sensors. Not all of the types that the Qt Sensors API supports may be available. There may also be types available that are not defined in the Qt Sensors API. The types of sensors available on a device is found using the sensorTypes() function.

For a list of built-in sensor types, see the Sensor Classes section below.

Common Conventions

Unless specified otherwise, Qt Sensors uses the Right Hand Cartesian coordinate system .

To allow for measurements in all 6 directions, negative values are used.

Where rotation around an axis is used, the rotation shall be expressed as a Right Hand rotation.

In general, sensor data is oriented relative to nativeOrientation , that is to the top of the device when the device is held in its natural orientation (normally when the device logo appears the right side up). If values are to be displayed on the screen, the values may need to be transformed so that they match the user interface orientation. A sensor may define its data as being oriented to the UI. This will be noted in the documentation for the sensor.

Using a Sensor

The life cycle of a QSensor is typically:

• Create an instance of QSensor or one of its sub-classes on the stack or heap.

• Setup as required by the application.

• Start receiving values.

• Sensor data is used by the application.

• Stop receiving values.

Here is an example of creating a sensor on the heap and on the stack.

// On the heap (deleted when this object is deleted)
QAccelerometer *sensor = new QAccelerometer(this);

// On the stack (deleted when the current scope ends)
QOrientationSensor orient_sensor;

Accessing Sensor Data in a Generic Fashion

The preferred way to deal with sensor data is via the Reading Classes . However, sometimes this may not be possible. For example, you may be deploying an application to a device that has a new sensor type but no C++ header describing the reading class is available.

Thanks to Qt’s property system you can still access the sensor data. You need to know 3 pieces of information in order to do this:

• The sensor type.

• The property name or index.

• The property type or a comparable type.

For example, here is an example of how you can access a property of the accelerometer. This code does not require any compile-time links to QAccelerometer or QAccelerometerReading .

// start the sensor
QSensor sensor("QAccelerometer");
sensor.start();

// later
QSensorReading *reading = sensor.reading();
qreal x = reading->property("x").value<qreal>();
qreal y = reading->value(1).value<qreal>();

You can discover all of this information at runtime too. The sensor_explorer example shows you information about available sensors.

Front End, Back End

The Qt Sensors API has a front end, for application developers to use and a back end, where device implementors write code to access their hardware. As an application developer you do not need to access the back end though it may be useful to understand how it works.

Commands from the application are delivered through QSensor and then down to the device plugin. Data comes back through the QSensorReading class.

More information about the back end can be found in Qt Sensors Backend .

Main Classes

The primary classes that make up the Qt Sensors API.

PySide2.QtSensors.QSensor	The QSensor class represents a single hardware sensor.
PySide2.QtSensors.QSensorFilter	The QSensorFilter class provides an efficient callback facility for asynchronous notifications of sensor changes.
PySide2.QtSensors.QSensorReading	The QSensorReading class holds the readings from the sensor.

Reading Classes

The best way to access sensor data is via one of these classes.

PySide2.QtSensors.QAccelerometerReading	The QAccelerometerReading class reports on linear acceleration along the X, Y and Z axes.
PySide2.QtSensors.QAltimeterReading	The QAltimeterReading class holds readings from the altimeter sensor.
PySide2.QtSensors.QAmbientLightReading	The QAmbientLightReading class represents one reading from the ambient light sensor.
PySide2.QtSensors.QAmbientTemperatureReading	The QAmbientTemperatureReading class holds readings of the ambient temperature.
PySide2.QtSensors.QCompassReading	The QCompassReading class represents one reading from a compass.
PySide2.QtSensors.QDistanceReading	The QDistanceReading class holds distance reading in cm from the proximity sensor.
PySide2.QtSensors.QGyroscopeReading	The QGyroscopeReading class represents one reading from the gyroscope sensor.
PySide2.QtSensors.QHolsterReading	The QHolsterReading class holds readings from the holster sensor.
PySide2.QtSensors.QHumidityReading	The QHumidityReading class holds readings from the humidity sensor.
PySide2.QtSensors.QIRProximityReading	The QIRProximityReading class holds readings from the IR proximity sensor.
PySide2.QtSensors.QLidReading	The QLidReading class holds readings from the Lid sensor.
PySide2.QtSensors.QLightReading	The QLightReading class represents one reading from the light sensor.
PySide2.QtSensors.QMagnetometerReading	The QMagnetometerReading class represents one reading from the magnetometer.
PySide2.QtSensors.QOrientationReading	The QOrientationReading class represents one reading from the orientation sensor.
PySide2.QtSensors.QPressureReading	The QPressureReading class holds readings from the pressure sensor.
PySide2.QtSensors.QProximityReading	The QProximityReading class represents one reading from the proximity sensor.
PySide2.QtSensors.QRotationReading	The QRotationReading class represents one reading from the rotation sensor.
PySide2.QtSensors.QTapReading	The QTapReading class represents one reading from the tap sensor.
PySide2.QtSensors.QTiltReading	The QTiltReading class holds readings from the tilt sensor.

Sensor Classes

These classes provide convenience wrappers that reduce the need for casting. Each of these classes represents a sensor type that the Qt Sensors API knows about. Note that additional types may be made available at run-time. See Sensor Types for more information.

PySide2.QtSensors.QAccelerometer	The QAccelerometer class is a convenience wrapper around QSensor.
PySide2.QtSensors.QAltimeter	The QAltimeter class is a convenience wrapper around QSensor.
PySide2.QtSensors.QAmbientLightSensor	The QAmbientLightSensor class is a convenience wrapper around QSensor.
PySide2.QtSensors.QAmbientTemperatureSensor	The QAmbientTemperatureSensor class is a convenience wrapper around QSensor.
PySide2.QtSensors.QCompass	The QCompass class is a convenience wrapper around QSensor.
PySide2.QtSensors.QDistanceSensor	The QDistanceSensor class is a convenience wrapper around QSensor.
PySide2.QtSensors.QGyroscope	The QGyroscope class is a convenience wrapper around QSensor.
PySide2.QtSensors.QHolsterSensor	The QHolsterSensor class is a convenience wrapper around QSensor.
PySide2.QtSensors.QHumiditySensor	The QHumiditySensor class is a convenience wrapper around QSensor.
PySide2.QtSensors.QIRProximitySensor	The QIRProximitySensor class is a convenience wrapper around QSensor.
PySide2.QtSensors.QLidSensor	The QLidSensor class is a convenience wrapper around QSensor.
PySide2.QtSensors.QLightSensor	The QLightSensor class is a convenience wrapper around QSensor.
PySide2.QtSensors.QMagnetometer	The QMagnetometer class is a convenience wrapper around QSensor.
PySide2.QtSensors.QOrientationSensor	The QOrientationSensor class is a convenience wrapper around QSensor.
PySide2.QtSensors.QPressureSensor	The QPressureSensor class is a convenience wrapper around QSensor.
PySide2.QtSensors.QProximitySensor	The QProximitySensor class is a convenience wrapper around QSensor.
PySide2.QtSensors.QRotationSensor	The QRotationSensor class is a convenience wrapper around QSensor.
PySide2.QtSensors.QTapSensor	The QTapSensor class is a convenience wrapper around QSensor.
PySide2.QtSensors.QTiltSensor	The QTiltSensor class is a convenience wrapper around QSensor.

Filter Classes

As with the sensor classes, these provide convenience wrappers that reduce the need for casting.

PySide2.QtSensors.QAccelerometerFilter	The QAccelerometerFilter class is a convenience wrapper around QSensorFilter.
PySide2.QtSensors.QAltimeterFilter	The QAltimeterFilter class is a convenience wrapper around QSensorFilter.
PySide2.QtSensors.QAmbientLightFilter	The QAmbientLightFilter class is a convenience wrapper around QSensorFilter.
PySide2.QtSensors.QAmbientTemperatureFilter	The QAmbientTemperatureFilter class is a convenience wrapper around QSensorFilter.
PySide2.QtSensors.QCompassFilter	The QCompassFilter class is a convenience wrapper around QSensorFilter.
PySide2.QtSensors.QDistanceFilter	The QDistanceFilter class is a convenience wrapper around QSensorFilter.
PySide2.QtSensors.QGyroscopeFilter	The QGyroscopeFilter class is a convenience wrapper around QSensorFilter.
PySide2.QtSensors.QHolsterFilter	The QHolsterFilter class is a convenience wrapper around QSensorFilter.
PySide2.QtSensors.QHumidityFilter	The QHumidityFilter class is a convenience wrapper around QSensorFilter.
PySide2.QtSensors.QIRProximityFilter	The QIRProximityFilter class is a convenience wrapper around QSensorFilter.
PySide2.QtSensors.QLidFilter	The QLidFilter class is a convenience wrapper around QSensorFilter.
PySide2.QtSensors.QLightFilter	The QLightFilter class is a convenience wrapper around QSensorFilter.
PySide2.QtSensors.QMagnetometerFilter	The QMagnetometerFilter class is a convenience wrapper around QSensorFilter.
PySide2.QtSensors.QOrientationFilter	The QOrientationFilter class is a convenience wrapper around QSensorFilter.
PySide2.QtSensors.QPressureFilter	The QPressureFilter class is a convenience wrapper around QSensorFilter.
PySide2.QtSensors.QProximityFilter	The QProximityFilter class is a convenience wrapper around QSensorFilter.
PySide2.QtSensors.QRotationFilter	The QRotationFilter class is a convenience wrapper around QSensorFilter.
PySide2.QtSensors.QTapFilter	The QTapFilter class is a convenience wrapper around QSensorFilter.
PySide2.QtSensors.QTiltFilter	The QTiltFilter class is a convenience wrapper around QSensorFilter.