PX4-Autopilot/src/examples/fake_magnetometer/FakeMagnetometer.cpp

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#include "FakeMagnetometer.hpp"

#include <lib/world_magnetic_model/geo_mag_declination.h>

using namespace matrix;
using namespace time_literals;

FakeMagnetometer::FakeMagnetometer() :
	ModuleParams(nullptr),
	ScheduledWorkItem(MODULE_NAME, px4::wq_configurations::hp_default),
	_px4_mag(0, ROTATION_NONE)
{
	_px4_mag.set_device_type(DRV_MAG_DEVTYPE_MAGSIM);
}

bool FakeMagnetometer::init()
{
	ScheduleOnInterval(10_ms); // 100 Hz
	return true;
}

void FakeMagnetometer::Run()
{
	if (should_exit()) {
		ScheduleClear();
		exit_and_cleanup();
		return;
	}

	if (_vehicle_gps_position_sub.updated()) {
		vehicle_gps_position_s gps;

		if (_vehicle_gps_position_sub.copy(&gps)) {
			if (gps.eph < 1000) {

				const double lat = gps.lat / 1.e7;
				const double lon = gps.lon / 1.e7;

				// magnetic field data returned by the geo library using the current GPS position
				const float mag_declination_gps = get_mag_declination_radians(lat, lon);
				const float mag_inclination_gps = get_mag_inclination_radians(lat, lon);
				const float mag_strength_gps = get_mag_strength_gauss(lat, lon);

				_mag_earth_pred = Dcmf(Eulerf(0, -mag_inclination_gps, mag_declination_gps)) * Vector3f(mag_strength_gps, 0, 0);

				_mag_earth_available = true;
			}
		}
	}

	if (_mag_earth_available) {
		vehicle_attitude_s attitude;

		if (_vehicle_attitude_sub.update(&attitude)) {
			Vector3f expected_field = Dcmf{Quatf{attitude.q}} .transpose() * _mag_earth_pred;

			_px4_mag.update(hrt_absolute_time(), expected_field(0), expected_field(1), expected_field(2));
		}
	}
}

int FakeMagnetometer::task_spawn(int argc, char *argv[])
{
	FakeMagnetometer *instance = new FakeMagnetometer();

	if (instance) {
		_object.store(instance);
		_task_id = task_id_is_work_queue;

		if (instance->init()) {
			return PX4_OK;
		}

	} else {
		PX4_ERR("alloc failed");
	}

	delete instance;
	_object.store(nullptr);
	_task_id = -1;

	return PX4_ERROR;
}

int FakeMagnetometer::custom_command(int argc, char *argv[])
{
	return print_usage("unknown command");
}

int FakeMagnetometer::print_usage(const char *reason)
{
	if (reason) {
		PX4_WARN("%s\n", reason);
	}

	PRINT_MODULE_DESCRIPTION(
		R"DESCR_STR(
### Description
Publish the earth magnetic field as a fake magnetometer (sensor_mag).
Requires vehicle_attitude and vehicle_gps_position.
)DESCR_STR");

	PRINT_MODULE_USAGE_NAME("fake_magnetometer", "driver");
	PRINT_MODULE_USAGE_COMMAND("start");
	PRINT_MODULE_USAGE_DEFAULT_COMMANDS();
	return 0;
}

extern "C" __EXPORT int fake_magnetometer_main(int argc, char *argv[])
{
	return FakeMagnetometer::main(argc, argv);
}