ardupilot/libraries/AP_HAL_ChibiOS/DSP.h

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/*
* This file is free software: you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the
* Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This file is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
* See the GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program. If not, see <http://www.gnu.org/licenses/>.
*
* Code by Andy Piper and the betaflight team
*/
#pragma once
#include <AP_HAL/AP_HAL.h>
#include "AP_HAL_ChibiOS_Namespace.h"
#if HAL_WITH_DSP
#include <arm_math.h>
#define DEBUG_FFT 0
// ChibiOS implementation of FFT analysis to run on STM32 processors
class ChibiOS::DSP : public AP_HAL::DSP {
public:
// initialise an FFT instance
virtual FFTWindowState* fft_init(uint16_t window_size, uint16_t sample_rate) override;
// start an FFT analysis
virtual void fft_start(FFTWindowState* state, const float* samples, uint16_t buffer_index, uint16_t buffer_size) override;
// perform remaining steps of an FFT analysis
virtual uint16_t fft_analyse(FFTWindowState* state, uint16_t start_bin, uint16_t end_bin, uint8_t harmonics, float noise_att_cutoff) override;
// STM32-based FFT state
class FFTWindowStateARM : public AP_HAL::DSP::FFTWindowState {
friend class ChibiOS::DSP;
protected:
FFTWindowStateARM(uint16_t window_size, uint16_t sample_rate);
~FFTWindowStateARM();
private:
// underlying CMSIS data structure for FFT analysis
arm_rfft_fast_instance_f32 _fft_instance;
};
protected:
void vector_max_float(const float* vin, uint16_t len, float* maxValue, uint16_t* maxIndex) const override {
uint32_t mindex;
arm_max_f32(vin, len, maxValue, &mindex);
*maxIndex = mindex;
}
void vector_scale_float(const float* vin, float scale, float* vout, uint16_t len) const override {
arm_scale_f32(vin, scale, vout, len);
}
private:
// following are the six independent steps for calculating an FFT
void step_hanning(FFTWindowStateARM* fft, const float* samples, uint16_t buffer_index, uint16_t buffer_size);
void step_arm_cfft_f32(FFTWindowStateARM* fft);
void step_bitreversal(FFTWindowStateARM* fft);
void step_stage_rfft_f32(FFTWindowStateARM* fft);
void step_arm_cmplx_mag_f32(FFTWindowStateARM* fft, uint16_t start_bin, uint16_t end_bin, uint8_t harmonics, float noise_att_cutoff);
uint16_t step_calc_frequencies_f32(FFTWindowStateARM* fft, uint16_t start_bin, uint16_t end_bin);
// candan's frequency interpolator
float calculate_candans_estimator(const FFTWindowStateARM* fft, uint16_t k) const;
#if DEBUG_FFT
class StepTimer {
public:
uint32_t _timer_total;
uint32_t _timer_avg;
uint8_t _time_ticks;
void time(uint32_t start);
};
uint32_t _output_count;
StepTimer _hanning_timer;
StepTimer _arm_cfft_f32_timer;
StepTimer _bitreversal_timer;
StepTimer _stage_rfft_f32_timer;
StepTimer _arm_cmplx_mag_f32_timer;
StepTimer _step_calc_frequencies;
#endif
};
#endif