create fake_magnetometer "driver" to publish magnetic field in body frame

- this can be helpful for orienting new unknown magnetometers
 - requires attitude and GPS position

boards/px4/fmu-v4/default.cmake

@@ -114,6 +114,7 @@ px4_add_board(
 		ver
 		work_queue
 	EXAMPLES
+		fake_magnetometer
 		fixedwing_control # Tutorial code from https://px4.io/dev/example_fixedwing_control
 		hello
 		hwtest # Hardware test

boards/px4/fmu-v5/default.cmake

@@ -118,6 +118,7 @@ px4_add_board(
 		ver
 		work_queue
 	EXAMPLES
+		fake_magnetometer
 		fixedwing_control # Tutorial code from https://px4.io/dev/example_fixedwing_control
 		hello
 		hwtest # Hardware test

boards/px4/sitl/default.cmake

@@ -75,6 +75,7 @@ px4_add_board(
 		work_queue
 	EXAMPLES
 		dyn_hello # dynamically loading modules example
+		fake_magnetometer
 		fixedwing_control # Tutorial code from https://px4.io/dev/example_fixedwing_control
 		hello
 		#hwtest # Hardware test

src/examples/fake_magnetometer/CMakeLists.txt

@@ -0,0 +1,46 @@
+############################################################################
+#
+#   Copyright (c) 2020 PX4 Development Team. All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions
+# are met:
+#
+# 1. Redistributions of source code must retain the above copyright
+#    notice, this list of conditions and the following disclaimer.
+# 2. Redistributions in binary form must reproduce the above copyright
+#    notice, this list of conditions and the following disclaimer in
+#    the documentation and/or other materials provided with the
+#    distribution.
+# 3. Neither the name PX4 nor the names of its contributors may be
+#    used to endorse or promote products derived from this software
+#    without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+# FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+# COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+# BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+# OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+# AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+# POSSIBILITY OF SUCH DAMAGE.
+#
+############################################################################
+
+px4_add_module(
+	MODULE examples__fake_magnetometer
+	MAIN fake_magnetometer
+	COMPILE_FLAGS
+	SRCS
+		FakeMagnetometer.cpp
+		FakeMagnetometer.hpp
+	DEPENDS
+		drivers_magnetometer
+		ecl_geo
+		git_ecl
+		px4_work_queue
+)

src/examples/fake_magnetometer/FakeMagnetometer.cpp

@@ -0,0 +1,146 @@
+/****************************************************************************
+ *
+ *   Copyright (c) 2020 PX4 Development Team. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name PX4 nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+#include "FakeMagnetometer.hpp"
+
+#include <lib/ecl/geo_lookup/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, ORB_PRIO_MIN, ROTATION_NONE)
+{
+	_px4_mag.set_device_type(DRV_MAG_DEVTYPE_MAGSIM);
+	_px4_mag.set_external(false);
+}
+
+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 = math::radians(get_mag_declination(lat, lon));
+				const float mag_inclination_gps = math::radians(get_mag_inclination(lat, lon));
+				const float mag_strength_gps = 0.01f * get_mag_strength(lat, lon); // centi-Gauss (micro-Tesla) -> Gauss
+
+				_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);
+}

src/examples/fake_magnetometer/FakeMagnetometer.hpp

@@ -0,0 +1,82 @@
+/****************************************************************************
+ *
+ *   Copyright (c) 2020 PX4 Development Team. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name PX4 nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/**
+ * @file FakeMagnetometer.cpp
+ *
+ * Publish the earth magnetic field as a fake magnetometer (sensor_mag).
+ * Requires vehicle_attitude and vehicle_gps_position
+ *
+ */
+
+#pragma once
+
+#include <px4_platform_common/defines.h>
+#include <px4_platform_common/module.h>
+#include <px4_platform_common/module_params.h>
+#include <px4_platform_common/posix.h>
+#include <px4_platform_common/px4_work_queue/ScheduledWorkItem.hpp>
+#include <lib/drivers/magnetometer/PX4Magnetometer.hpp>
+#include <uORB/Subscription.hpp>
+#include <uORB/topics/vehicle_attitude.h>
+#include <uORB/topics/vehicle_gps_position.h>
+
+class FakeMagnetometer : public ModuleBase<FakeMagnetometer>, public ModuleParams, public px4::ScheduledWorkItem
+{
+public:
+	FakeMagnetometer();
+	~FakeMagnetometer() override = default;
+
+	/** @see ModuleBase */
+	static int task_spawn(int argc, char *argv[]);
+
+	/** @see ModuleBase */
+	static int custom_command(int argc, char *argv[]);
+
+	/** @see ModuleBase */
+	static int print_usage(const char *reason = nullptr);
+
+	bool init();
+
+private:
+	void Run() override;
+
+	PX4Magnetometer _px4_mag;
+
+	bool _mag_earth_available{false};
+
+	matrix::Vector3f _mag_earth_pred{};
+
+	uORB::Subscription _vehicle_attitude_sub{ORB_ID(vehicle_attitude)};
+	uORB::Subscription _vehicle_gps_position_sub{ORB_ID(vehicle_gps_position)};
+};