System State API

Related C++ Header in the Auterion SDK:<auterion_sdk/system_state/system_state.hpp>

Auterion SDK provides an interface for subscribing to various states of the vehicle, such as the current position, attitude or battery status. These states can be queried by polling or by registering callbacks.

Available data

The following states are available through the system state API:

State	Data type
Local Position	auterion::LocalPosition
Global Position	auterion::GlobalPosition
Attitude	Eigen::Quaternionf
Angular Rates	auterion::AngularRates
Armed	bool
Home Position	auterion::HomePosition
Battery	auterion::BatteryStatus
VTOL State	auterion::VtolState
Manual Input	auterion::ManualInput
Wind	auterion::Wind
Airspeed	auterion::Airspeed

Subscribing to system states

Instantiate an auterion::SystemState object, then specify the states to subscribe to.

auterion::SystemState system_state(sdk);
// Subscribe to the vehicle's local position, armed state and battery status
system_state.subscribeLocalPosition()
            .subscribeArmed()
            .subscribeBattery();

Each subscribed state will have an auterion::Subcription object associated with it. The SystemState class has accessor functions for each of the supported states, for example: system_state.localPosition(). These will be used to query the states and register callbacks.

Querying the latest state

Poll the latest state value by calling the last() function of the corresponding Subscription. The return type will depend on what state is being queried.

auterion::LocalPosition local_position = system_state.localPosition().last();

Note that last() will throw an exception if the state has not been subscribed to or if no data has been received for 500ms. To check that data is available and valid, use the isLastValid() function.

if (system_state.localPosition().isLastValid()) {
    auterion::LocalPosition local_position = system_state.localPosition().last();
}

Registering callbacks

When subscribing to a state, a callback can be provided that will run whenever new data is available.

auterion::SystemState system_state(sdk);
// Subscribe to the vehicle's local position, armed state and battery status,
// and register a callback for the armed state.
system_state.subscribeLocalPosition()
            .subscribeArmed([](bool is_armed) {
                std::cout << is_armed ? "Armed" : "Disarmed" << std::endl;
            })
            .subscribeBattery();

It is possible to register one or more callbacks after subscribing to a state with the onUpdate() method of the appropriate Subscription.

// Register an additional callback for the armed state
system_state.armed().onUpdate([](bool is_armed) {
    std::cout << "Armed? " << is_armed ? "yes" : "no" << std::endl;
});

// Register a callback for the battery state
system_state.battery().onUpdate([](auterion::BatteryStatus battery_status) {
    std::cout << "Battery voltage: " << battery_status.voltage_v << "V" << std::endl;
});