src/main/common/filter.h

   1 /*
   2  * This file is part of Cleanflight.
   3  *
   4  * Cleanflight is free software: you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License as published by
   6  * the Free Software Foundation, either version 3 of the License, or
   7  * (at your option) any later version.
   8  *
   9  * Cleanflight is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with Cleanflight.  If not, see <http://www.gnu.org/licenses/>.
  16  */
  17
  18 #pragma once
  19
  20 // Don't use it on F1 and F3 to lower RAM usage
  21 // FIR/Denoise filter can be cleaned up in the future as it is rarely used and used to be experimental
  22 #if (defined(STM32F1) || defined(STM32F3))
  23 #define MAX_FIR_DENOISE_WINDOW_SIZE 1
  24 #else
  25 #define MAX_FIR_DENOISE_WINDOW_SIZE 120
  26 #endif
  27
  28 struct filter_s;
  29 typedef struct filter_s filter_t;
  30
  31 typedef struct pt1Filter_s {
  32     float state;
  33     float k;
  34 } pt1Filter_t;
  35
  36 typedef struct slewFilter_s {
  37     float state;
  38     float slewLimit;
  39     float threshold;
  40 } slewFilter_t;
  41
  42 /* this holds the data required to update samples thru a filter */
  43 typedef struct biquadFilter_s {
  44     float b0, b1, b2, a1, a2;
  45     float x1, x2, y1, y2;
  46 } biquadFilter_t;
  47
  48 typedef struct firFilterDenoise_s {
  49     int filledCount;
  50     int targetCount;
  51     int index;
  52     float movingSum;
  53     float state[MAX_FIR_DENOISE_WINDOW_SIZE];
  54 } firFilterDenoise_t;
  55
  56 typedef struct fastKalman_s {
  57     float q;       // process noise covariance
  58     float r;       // measurement noise covariance
  59     float p;       // estimation error covariance matrix
  60     float k;       // kalman gain
  61     float x;       // state
  62     float lastX;   // previous state
  63 } fastKalman_t;
  64
  65 typedef enum {
  66     FILTER_PT1 = 0,
  67     FILTER_BIQUAD,
  68     FILTER_FIR,
  69     FILTER_SLEW
  70 } filterType_e;
  71
  72 typedef enum {
  73     FILTER_LPF,
  74     FILTER_NOTCH,
  75     FILTER_BPF,
  76 } biquadFilterType_e;
  77
  78 typedef struct firFilter_s {
  79     float *buf;
  80     const float *coeffs;
  81     float movingSum;
  82     uint8_t index;
  83     uint8_t count;
  84     uint8_t bufLength;
  85     uint8_t coeffsLength;
  86 } firFilter_t;
  87
  88 typedef float (*filterApplyFnPtr)(filter_t *filter, float input);
  89
  90 float nullFilterApply(filter_t *filter, float input);
  91
  92 void biquadFilterInitLPF(biquadFilter_t *filter, float filterFreq, uint32_t refreshRate);
  93 void biquadFilterInit(biquadFilter_t *filter, float filterFreq, uint32_t refreshRate, float Q, biquadFilterType_e filterType);
  94 void biquadFilterUpdate(biquadFilter_t *filter, float filterFreq, uint32_t refreshRate, float Q, biquadFilterType_e filterType);
  95 float biquadFilterApplyDF1(biquadFilter_t *filter, float input);
  96 float biquadFilterApply(biquadFilter_t *filter, float input);
  97 float filterGetNotchQ(uint16_t centerFreq, uint16_t cutoff);
  98
  99 void biquadRCFIR2FilterInit(biquadFilter_t *filter, uint16_t f_cut, float dT);
 100
 101 void fastKalmanInit(fastKalman_t *filter, float q, float r, float p);
 102 float fastKalmanUpdate(fastKalman_t *filter, float input);
 103
 104 // not exactly correct, but very very close and much much faster
 105 #define filterGetNotchQApprox(centerFreq, cutoff)   ((float)(cutoff * centerFreq) / ((float)(centerFreq - cutoff) * (float)(centerFreq + cutoff)))
 106
 107 void pt1FilterInit(pt1Filter_t *filter, uint8_t f_cut, float dT);
 108 float pt1FilterApply(pt1Filter_t *filter, float input);
 109
 110 void slewFilterInit(slewFilter_t *filter, float slewLimit, float threshold);
 111 float slewFilterApply(slewFilter_t *filter, float input);
 112
 113 void firFilterInit(firFilter_t *filter, float *buf, uint8_t bufLength, const float *coeffs);
 114 void firFilterInit2(firFilter_t *filter, float *buf, uint8_t bufLength, const float *coeffs, uint8_t coeffsLength);
 115 void firFilterUpdate(firFilter_t *filter, float input);
 116 void firFilterUpdateAverage(firFilter_t *filter, float input);
 117 float firFilterApply(const firFilter_t *filter);
 118 float firFilterUpdateAndApply(firFilter_t *filter, float input);
 119 float firFilterCalcPartialAverage(const firFilter_t *filter, uint8_t count);
 120 float firFilterCalcMovingAverage(const firFilter_t *filter);
 121 float firFilterLastInput(const firFilter_t *filter);
 122
 123 void firFilterDenoiseInit(firFilterDenoise_t *filter, uint8_t gyroSoftLpfHz, uint16_t targetLooptime);
 124 float firFilterDenoiseUpdate(firFilterDenoise_t *filter, float input);