examples: add Gyro FFT using CMSIS 5 on Cortex-m (#15104)

- this is a work in progress experiment to compute real time FFTs from raw gyro FIFO data on Cortex-m hardware (stm32f4/f7/h7, etc)

.gitmodules

@@ -51,3 +51,6 @@
 [submodule "Tools/jsbsim_bridge"]
 	path = Tools/jsbsim_bridge
 	url = https://github.com/PX4/px4-jsbsim-bridge.git
+[submodule "src/examples/gyro_fft/CMSIS_5"]
+	path = src/examples/gyro_fft/CMSIS_5
+	url = https://github.com/ARM-software/CMSIS_5.git

Tools/astyle/files_to_check_code_style.sh

@@ -16,6 +16,7 @@ exec find boards msg src platforms test \
     -path src/lib/ecl -prune -o \
     -path src/lib/matrix -prune -o \
     -path src/lib/systemlib/uthash -prune -o \
+    -path src/examples/gyro_fft/CMSIS_5 -prune -o \
     -path src/modules/micrortps_bridge/micro-CDR -prune -o \
     -path src/modules/micrortps_bridge/microRTPS_client -prune -o \
     -path test/mavsdk_tests/catch2 -prune -o \

boards/px4/fmu-v4/default.cmake

@@ -117,8 +117,10 @@ px4_add_board(
 		ver
 		work_queue
 	EXAMPLES
+		fake_gyro
 		fake_magnetometer
 		fixedwing_control # Tutorial code from https://px4.io/dev/example_fixedwing_control
+		gyro_fft
 		hello
 		hwtest # Hardware test
 		#matlab_csv_serial

boards/px4/fmu-v5/default.cmake

@@ -121,8 +121,10 @@ px4_add_board(
 		ver
 		work_queue
 	EXAMPLES
+		fake_gyro
 		fake_magnetometer
 		fixedwing_control # Tutorial code from https://px4.io/dev/example_fixedwing_control
+		gyro_fft
 		hello
 		hwtest # Hardware test
 		#matlab_csv_serial

msg/CMakeLists.txt

@@ -119,6 +119,8 @@ set(msg_files
 	sensor_correction.msg
 	sensor_gps.msg
 	sensor_gyro.msg
+	sensor_gyro_fft.msg
+	sensor_gyro_fft_axis.msg
 	sensor_gyro_fifo.msg
 	sensor_mag.msg
 	sensor_preflight_mag.msg

msg/sensor_gyro_fft.msg

@@ -0,0 +1,15 @@
+uint64 timestamp          # time since system start (microseconds)
+uint64 timestamp_sample
+
+uint32 device_id          # unique device ID for the sensor that does not change between power cycles
+
+float32 dt                # delta time between samples (microseconds)
+float32 scale
+
+uint8 samples             # number of valid samples
+
+uint8 peak_index
+
+float32 peak_frequency_0
+float32 peak_frequency_1
+float32 peak_frequency_2

msg/sensor_gyro_fft_axis.msg

@@ -0,0 +1,23 @@
+uint64 timestamp          # time since system start (microseconds)
+uint64 timestamp_sample
+
+uint32 device_id          # unique device ID for the sensor that does not change between power cycles
+
+float32 dt                # delta time between samples (microseconds)
+
+uint16 samples             # number of valid samples
+
+float32 resolution_hz
+
+int16[128] fft
+
+uint16 peak_index
+uint16 peak_index_quinns
+
+float32 peak_frequency
+float32 peak_frequency_quinns
+
+uint8 AXIS_X = 0
+uint8 AXIS_Y = 1
+uint8 AXIS_Z = 2
+uint8 axis

msg/tools/uorb_rtps_message_ids.yaml

@@ -285,6 +285,10 @@ rtps:
     id: 135
   - msg: generator_status
     id: 136
+  - msg: sensor_gyro_fft
+    id: 137
+  - msg: sensor_gyro_fft_axis
+    id: 138
   ########## multi topics: begin ##########
   - msg: actuator_controls_0
     id: 150

src/examples/fake_gyro/CMakeLists.txt

@@ -0,0 +1,44 @@
+############################################################################
+#
+#   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 modules__fake_gyro
+	MAIN fake_gyro
+	COMPILE_FLAGS
+		${MAX_CUSTOM_OPT_LEVEL}
+	SRCS
+		FakeGyro.cpp
+		FakeGyro.hpp
+	DEPENDS
+		px4_work_queue
+)

src/examples/fake_gyro/FakeGyro.cpp

@@ -0,0 +1,132 @@
+/****************************************************************************
+ *
+ *   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 "FakeGyro.hpp"
+
+using namespace time_literals;
+
+FakeGyro::FakeGyro() :
+	ModuleParams(nullptr),
+	ScheduledWorkItem(MODULE_NAME, px4::wq_configurations::hp_default)
+{
+}
+
+bool FakeGyro::init()
+{
+	ScheduleOnInterval(SENSOR_RATE, SENSOR_RATE);
+	return true;
+}
+
+void FakeGyro::Run()
+{
+	if (should_exit()) {
+		ScheduleClear();
+		exit_and_cleanup();
+		return;
+	}
+
+	sensor_gyro_fifo_s sensor_gyro_fifo{};
+	sensor_gyro_fifo.timestamp_sample = hrt_absolute_time();
+	sensor_gyro_fifo.device_id = 1;
+	sensor_gyro_fifo.samples = GYRO_RATE / (1e6f / SENSOR_RATE);
+	sensor_gyro_fifo.dt = 1e6f / GYRO_RATE; // 8 kHz fake gyro
+	sensor_gyro_fifo.scale = math::radians(2000.f) / static_cast<float>(INT16_MAX - 1); // 2000 degrees/second max
+
+	const float dt_s = sensor_gyro_fifo.dt / 1e6f;
+	const float x_freq = 15.f;  // 15 Hz x frequency
+	const float y_freq = 63.5f; // 63.5 Hz y frequency
+	const float z_freq = 99.f;  // 99 Hz z frequency
+
+	for (int n = 0; n < sensor_gyro_fifo.samples; n++) {
+		_time += dt_s;
+		const float k = 2.f * M_PI_F * _time;
+
+		sensor_gyro_fifo.x[n] = (INT16_MAX - 1) * sinf(k * x_freq);
+		sensor_gyro_fifo.y[n] = (INT16_MAX - 1) / 2 * sinf(k * y_freq);
+		sensor_gyro_fifo.z[n] = (INT16_MAX - 1) * cosf(k * z_freq);
+	}
+
+	sensor_gyro_fifo.timestamp = hrt_absolute_time();
+	_sensor_gyro_fifo_pub.publish(sensor_gyro_fifo);
+}
+
+int FakeGyro::task_spawn(int argc, char *argv[])
+{
+	FakeGyro *instance = new FakeGyro();
+
+	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 FakeGyro::custom_command(int argc, char *argv[])
+{
+	return print_usage("unknown command");
+}
+
+int FakeGyro::print_usage(const char *reason)
+{
+	if (reason) {
+		PX4_WARN("%s\n", reason);
+	}
+
+	PRINT_MODULE_DESCRIPTION(
+		R"DESCR_STR(
+### Description
+
+)DESCR_STR");
+
+	PRINT_MODULE_USAGE_NAME("fake_gyro", "driver");
+	PRINT_MODULE_USAGE_COMMAND("start");
+	PRINT_MODULE_USAGE_DEFAULT_COMMANDS();
+	return 0;
+}
+
+extern "C" __EXPORT int fake_gyro_main(int argc, char *argv[])
+{
+	return FakeGyro::main(argc, argv);
+}

src/examples/fake_gyro/FakeGyro.hpp

@@ -0,0 +1,71 @@
+/****************************************************************************
+ *
+ *   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.
+ *
+ ****************************************************************************/
+
+#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 <uORB/PublicationMulti.hpp>
+#include <uORB/Subscription.hpp>
+#include <uORB/topics/sensor_gyro_fifo.h>
+
+class FakeGyro : public ModuleBase<FakeGyro>, public ModuleParams, public px4::ScheduledWorkItem
+{
+public:
+	FakeGyro();
+	~FakeGyro() 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:
+	static constexpr uint32_t SENSOR_RATE = 1250;
+	static constexpr float GYRO_RATE = 8000;
+
+	void Run() override;
+
+	uORB::PublicationMulti<sensor_gyro_fifo_s> _sensor_gyro_fifo_pub{ORB_ID(sensor_gyro_fifo)};
+
+	float _time{0.f};
+};

src/examples/gyro_fft/CMSIS_5

@@ -0,0 +1 @@
+Subproject commit 03a697980f808120f1b75bfe0a96c2dd31bafbbc

src/examples/gyro_fft/CMakeLists.txt

@@ -0,0 +1,107 @@
+############################################################################
+#
+#   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_git_submodule(TARGET git_cmsis_v5 PATH "${CMAKE_CURRENT_SOURCE_DIR}/CMSIS_5")
+
+# Needed to include the configBoot module
+# Define the path to CMSIS-DSP (ROOT is defined on command line when using cmake)
+set(ROOT ${CMAKE_CURRENT_SOURCE_DIR}/CMSIS_5)
+set(DSP ${ROOT}/CMSIS/DSP)
+
+set(GCC ON CACHE BOOL "")
+set(PLATFORM "FVP" CACHE STRING "")
+set(ARM_CPU ${ARCHITECTURE} CACHE STRING "Set ARM CPU. Default : cortex-m4")
+
+set(FASTMATH ON CACHE BOOL "")
+set(TRANSFORM ON CACHE BOOL "")
+#set(CONFIGTABLE ON CACHE BOOL "")
+#set(ALLFAST ON CACHE BOOL "")
+#set(ALLFFT ON CACHE BOOL "")
+
+add_compile_options(
+	#-Wno-strict-prototypes
+	-Wno-error
+
+	-DARM_FFT_ALLOW_TABLES
+
+	-DARM_ALL_FFT_TABLES
+	-DARM_TABLE_TWIDDLECOEF_Q15_128
+	-DARM_TABLE_BITREVIDX_FXT_128
+	-DARM_TABLE_REALCOEF_Q15
+
+	-DARMCM4_FP
+	-DARM_MATH_LOOPUNROLL
+	-DCORTEXM
+)
+
+add_compile_options($<$<COMPILE_LANGUAGE:C>:-Wno-nested-externs>)
+
+px4_add_module(
+	MODULE modules__gyro_fft
+	MAIN gyro_fft
+	STACK_MAIN
+		8192
+	COMPILE_FLAGS
+		${MAX_CUSTOM_OPT_LEVEL}
+	INCLUDES
+		${ROOT}/CMSIS/Core/Include
+		${DSP}/Include
+	SRCS
+		GyroFFT.cpp
+		GyroFFT.hpp
+
+		${DSP}/Source/BasicMathFunctions/arm_shift_q15.c
+
+		${DSP}/Source/CommonTables/arm_common_tables.c
+		${DSP}/Source/CommonTables/arm_const_structs.c
+
+		${DSP}/Source/ComplexMathFunctions/arm_cmplx_mult_cmplx_q15.c
+
+		${DSP}/Source/TransformFunctions/arm_bitreversal2.c
+
+		#${DSP}/Source/TransformFunctions/arm_cfft_init_q15.c
+		${DSP}/Source/TransformFunctions/arm_cfft_q15.c
+		${DSP}/Source/TransformFunctions/arm_cfft_radix4_q15.c
+
+		${DSP}/Source/TransformFunctions/arm_rfft_init_q15.c
+		${DSP}/Source/TransformFunctions/arm_rfft_q15.c
+		#${DSP}/Source/TransformFunctions/arm_rfft_radix4_q15.c
+
+		${DSP}/Source/SupportFunctions/arm_float_to_q15.c
+		${DSP}/Source/BasicMathFunctions/arm_mult_q15.c
+
+	DEPENDS
+		git_cmsis_v5
+		px4_work_queue
+)

src/examples/gyro_fft/GyroFFT.cpp

@@ -0,0 +1,310 @@
+/****************************************************************************
+ *
+ *   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 "GyroFFT.hpp"
+
+#include <drivers/drv_hrt.h>
+#include <mathlib/math/Limits.hpp>
+#include <mathlib/math/Functions.hpp>
+
+using namespace matrix;
+using namespace time_literals;
+using math::radians;
+
+GyroFFT::GyroFFT() :
+	ModuleParams(nullptr),
+	ScheduledWorkItem(MODULE_NAME, px4::wq_configurations::lp_default)
+{
+	for (int axis = 0; axis < 3; axis++) {
+		arm_rfft_init_q15(&_rfft_q15[axis], FFT_LENGTH, 0, 1);
+	}
+
+	// init Hanning window
+	float hanning_window[FFT_LENGTH];
+
+	for (int n = 0; n < FFT_LENGTH; n++) {
+		hanning_window[n] = 0.5f - 0.5f * cosf(2.f * M_PI_F * n / (FFT_LENGTH - 1));
+	}
+
+	arm_float_to_q15(hanning_window, _hanning_window, FFT_LENGTH);
+}
+
+GyroFFT::~GyroFFT()
+{
+	perf_free(_cycle_perf);
+	perf_free(_cycle_interval_perf);
+	perf_free(_fft_perf);
+	perf_free(_gyro_fifo_generation_gap_perf);
+}
+
+bool GyroFFT::init()
+{
+	if (!SensorSelectionUpdate(true)) {
+		PX4_ERR("sensor_gyro_fifo callback registration failed!");
+		return false;
+	}
+
+	return true;
+}
+
+bool GyroFFT::SensorSelectionUpdate(bool force)
+{
+	if (_sensor_selection_sub.updated() || force) {
+		sensor_selection_s sensor_selection{};
+		_sensor_selection_sub.copy(&sensor_selection);
+
+		if (_selected_sensor_device_id != sensor_selection.gyro_device_id) {
+			for (uint8_t i = 0; i < MAX_SENSOR_COUNT; i++) {
+				uORB::SubscriptionData<sensor_gyro_fifo_s> sensor_gyro_fifo_sub{ORB_ID(sensor_gyro_fifo), i};
+
+				if ((sensor_gyro_fifo_sub.get().device_id != 0)
+				    && (sensor_gyro_fifo_sub.get().device_id == sensor_selection.gyro_device_id)) {
+
+					if (_sensor_gyro_fifo_sub.ChangeInstance(i) && _sensor_gyro_fifo_sub.registerCallback()) {
+						return true;
+					}
+				}
+			}
+
+			PX4_ERR("unable to find or subscribe to selected sensor (%d)", sensor_selection.gyro_device_id);
+		}
+	}
+
+	return false;
+}
+
+// helper function used for frequency estimation
+static constexpr float tau(float x)
+{
+	float p1 = logf(3.f * powf(x, 2.f) + 6 * x + 1);
+	float part1 = x + 1 - sqrtf(2.f / 3.f);
+	float part2 = x + 1 + sqrtf(2.f / 3.f);
+	float p2 = logf(part1 / part2);
+	return (1.f / 4.f * p1 - sqrtf(6) / 24 * p2);
+}
+
+void GyroFFT::Run()
+{
+	if (should_exit()) {
+		_sensor_gyro_fifo_sub.unregisterCallback();
+		exit_and_cleanup();
+		return;
+	}
+
+	// backup schedule
+	ScheduleDelayed(500_ms);
+
+	perf_begin(_cycle_perf);
+	perf_count(_cycle_interval_perf);
+
+	// Check if parameters have changed
+	if (_parameter_update_sub.updated()) {
+		// clear update
+		parameter_update_s param_update;
+		_parameter_update_sub.copy(&param_update);
+
+		updateParams();
+	}
+
+	SensorSelectionUpdate();
+
+	// run on sensor gyro fifo updates
+	sensor_gyro_fifo_s sensor_gyro_fifo;
+
+	while (_sensor_gyro_fifo_sub.update(&sensor_gyro_fifo)) {
+
+		if (_sensor_gyro_fifo_sub.get_last_generation() != _gyro_last_generation + 1) {
+			// force reset if we've missed a sample
+			_fft_buffer_index[0] = 0;
+			_fft_buffer_index[1] = 0;
+			_fft_buffer_index[2] = 0;
+
+			perf_count(_gyro_fifo_generation_gap_perf);
+		}
+
+		_gyro_last_generation = _sensor_gyro_fifo_sub.get_last_generation();
+
+		const int N = sensor_gyro_fifo.samples;
+
+		for (int axis = 0; axis < 3; axis++) {
+			int16_t *input = nullptr;
+
+			switch (axis) {
+			case 0:
+				input = sensor_gyro_fifo.x;
+				break;
+
+			case 1:
+				input = sensor_gyro_fifo.y;
+				break;
+
+			case 2:
+				input = sensor_gyro_fifo.z;
+				break;
+			}
+
+			for (int n = 0; n < N; n++) {
+				int &buffer_index = _fft_buffer_index[axis];
+
+				_data_buffer[axis][buffer_index] = input[n] / 2;
+
+				buffer_index++;
+
+				// if we have enough samples, begin processing
+				if (buffer_index >= FFT_LENGTH) {
+
+					arm_mult_q15(_data_buffer[axis], _hanning_window, _fft_input_buffer, FFT_LENGTH);
+
+					perf_begin(_fft_perf);
+					arm_rfft_q15(&_rfft_q15[axis], _fft_input_buffer, _fft_outupt_buffer);
+					perf_end(_fft_perf);
+
+
+					// find peak location using Quinn's Second Estimator (2020-06-14: http://dspguru.com/dsp/howtos/how-to-interpolate-fft-peak/)
+					int16_t max_peak = 0;
+					uint16_t max_peak_index = 0;
+
+					// start at 1 to skip DC
+					for (uint16_t bucket_index = 1; bucket_index < FFT_LENGTH; bucket_index++) {
+						if (abs(_fft_outupt_buffer[bucket_index]) >= max_peak) {
+							max_peak_index = bucket_index;
+							max_peak = abs(_fft_outupt_buffer[bucket_index]);
+						}
+					}
+
+
+					int k = max_peak_index;
+					float divider = powf(_fft_outupt_buffer[k], 2.f);
+					float ap = (_fft_outupt_buffer[k + 1] * _fft_outupt_buffer[k]) / divider;
+					float dp = -ap  / (1.f - ap);
+					float am = (_fft_outupt_buffer[k - 1] * _fft_outupt_buffer[k]) / divider;
+
+					float dm = am / (1.f - am);
+					float d = (dp + dm) / 2 + tau(dp * dp) - tau(dm * dm);
+
+					float adjustedBinLocation = k + d;
+					float peakFreqAdjusted = (_gyro_sample_rate * adjustedBinLocation / (FFT_LENGTH * 2));
+
+
+					// publish sensor_gyro_fft_axis (one instance per axis)
+					sensor_gyro_fft_axis_s sensor_gyro_fft_axis{};
+					const int N_publish = math::min((unsigned)FFT_LENGTH,
+									sizeof(sensor_gyro_fft_axis_s::fft) / sizeof(sensor_gyro_fft_axis_s::fft[0]));
+					memcpy(sensor_gyro_fft_axis.fft, _fft_outupt_buffer, N_publish);
+
+					sensor_gyro_fft_axis.resolution_hz = _gyro_sample_rate / (FFT_LENGTH * 2);
+
+					sensor_gyro_fft_axis.peak_index = max_peak_index;
+					sensor_gyro_fft_axis.peak_frequency = max_peak_index * sensor_gyro_fft_axis.resolution_hz;
+
+					sensor_gyro_fft_axis.peak_index_quinns = adjustedBinLocation;
+					sensor_gyro_fft_axis.peak_frequency_quinns = peakFreqAdjusted;
+
+					sensor_gyro_fft_axis.samples = FFT_LENGTH;
+					sensor_gyro_fft_axis.dt = 1e6f / _gyro_sample_rate;
+					sensor_gyro_fft_axis.device_id = sensor_gyro_fifo.device_id;
+					sensor_gyro_fft_axis.axis = axis;
+					sensor_gyro_fft_axis.timestamp_sample = sensor_gyro_fifo.timestamp_sample;
+					sensor_gyro_fft_axis.timestamp = hrt_absolute_time();
+					_sensor_gyro_fft_axis_pub[axis].publish(sensor_gyro_fft_axis);
+
+					// reset
+					buffer_index = 0;
+				}
+			}
+		}
+	}
+
+	perf_end(_cycle_perf);
+}
+
+int GyroFFT::task_spawn(int argc, char *argv[])
+{
+	GyroFFT *instance = new GyroFFT();
+
+	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 GyroFFT::print_status()
+{
+	perf_print_counter(_cycle_perf);
+	perf_print_counter(_cycle_interval_perf);
+	perf_print_counter(_fft_perf);
+	perf_print_counter(_gyro_fifo_generation_gap_perf);
+	return 0;
+}
+
+int GyroFFT::custom_command(int argc, char *argv[])
+{
+	return print_usage("unknown command");
+}
+
+int GyroFFT::print_usage(const char *reason)
+{
+	if (reason) {
+		PX4_WARN("%s\n", reason);
+	}
+
+	PRINT_MODULE_DESCRIPTION(
+		R"DESCR_STR(
+### Description
+
+)DESCR_STR");
+
+	PRINT_MODULE_USAGE_NAME("gyro_fft", "system");
+	PRINT_MODULE_USAGE_COMMAND("start");
+	PRINT_MODULE_USAGE_DEFAULT_COMMANDS();
+
+	return 0;
+}
+
+extern "C" __EXPORT int gyro_fft_main(int argc, char *argv[])
+{
+	return GyroFFT::main(argc, argv);
+}

src/examples/gyro_fft/GyroFFT.hpp

@@ -0,0 +1,114 @@
+/****************************************************************************
+ *
+ *   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.
+ *
+ ****************************************************************************/
+
+#pragma once
+
+#include <lib/matrix/matrix/math.hpp>
+#include <lib/perf/perf_counter.h>
+#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 <uORB/Publication.hpp>
+#include <uORB/PublicationMulti.hpp>
+#include <uORB/Subscription.hpp>
+#include <uORB/SubscriptionCallback.hpp>
+#include <uORB/topics/parameter_update.h>
+#include <uORB/topics/sensor_gyro_fft.h>
+#include <uORB/topics/sensor_gyro_fft_axis.h>
+#include <uORB/topics/sensor_gyro_fifo.h>
+#include <uORB/topics/sensor_selection.h>
+
+#include "arm_math.h"
+#include "arm_const_structs.h"
+
+class GyroFFT : public ModuleBase<GyroFFT>, public ModuleParams, public px4::ScheduledWorkItem
+{
+public:
+	GyroFFT();
+	~GyroFFT() override;
+
+	/** @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);
+
+	/** @see ModuleBase::print_status() */
+	int print_status() override;
+
+	bool init();
+
+private:
+	void Run() override;
+	bool SensorSelectionUpdate(bool force = false);
+
+	static constexpr int MAX_SENSOR_COUNT = 3;
+
+	uORB::Publication<sensor_gyro_fft_s> _sensor_gyro_fft_pub{ORB_ID(sensor_gyro_fft)};
+	uORB::Publication<sensor_gyro_fft_axis_s> _sensor_gyro_fft_axis_pub[3] {
+		ORB_ID(sensor_gyro_fft_axis),
+		ORB_ID(sensor_gyro_fft_axis),
+		ORB_ID(sensor_gyro_fft_axis),
+	};
+
+	uORB::Subscription _parameter_update_sub{ORB_ID(parameter_update)};
+	uORB::Subscription _sensor_selection_sub{ORB_ID(sensor_selection)};
+
+	uORB::SubscriptionCallbackWorkItem _sensor_gyro_fifo_sub{this, ORB_ID(sensor_gyro_fifo)};
+
+	perf_counter_t _cycle_perf{perf_alloc(PC_ELAPSED, MODULE_NAME": cycle")};
+	perf_counter_t _cycle_interval_perf{perf_alloc(PC_INTERVAL, MODULE_NAME": cycle interval")};
+	perf_counter_t _fft_perf{perf_alloc(PC_ELAPSED, MODULE_NAME": FFT")};
+	perf_counter_t _gyro_fifo_generation_gap_perf{perf_alloc(PC_COUNT, MODULE_NAME": gyro FIFO data gap")};
+
+	uint32_t _selected_sensor_device_id{0};
+
+	static constexpr uint16_t FFT_LENGTH = 1024;
+	arm_rfft_instance_q15 _rfft_q15[3];
+
+	q15_t _data_buffer[3][FFT_LENGTH] {};
+	q15_t _hanning_window[FFT_LENGTH] {};
+	q15_t _fft_input_buffer[FFT_LENGTH] {};
+	q15_t _fft_outupt_buffer[FFT_LENGTH * 2] {};
+
+	float _gyro_sample_rate{8000}; // 8 kHz default
+
+	int _fft_buffer_index[3] {};
+
+	unsigned _gyro_last_generation{0};
+};

src/systemcmds/topic_listener/CMakeLists.txt

@@ -47,6 +47,7 @@ px4_add_module(
 	MODULE systemcmds__topic_listener
 	MAIN listener
 	COMPILE_FLAGS
+	STACK_MAIN 4096
 	INCLUDES
 		${CMAKE_CURRENT_SOURCE_DIR}
 		${CMAKE_CURRENT_BINARY_DIR}