Sensors

Common Conventions

Unless otherwise specified, sensors shall use 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 to the top of the device. 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 sensor 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;

 // 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>();