src/main/flight/lowpass.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
  21 #define LOWPASS_NUM_COEF 3
  22 #define LPF_ROUND(x) (x < 0 ? (x - 0.5f) : (x + 0.5f))
  23
  24 typedef struct lowpass_s {
  25     bool init;
  26     int16_t freq;                           // Normalized freq in 1/1000ths
  27     float bf[LOWPASS_NUM_COEF];
  28     float af[LOWPASS_NUM_COEF];
  29     int64_t b[LOWPASS_NUM_COEF];
  30     int64_t a[LOWPASS_NUM_COEF];
  31     int16_t coeff_shift;
  32     int16_t input_shift;
  33     int32_t input_bias;
  34     float xf[LOWPASS_NUM_COEF];
  35     float yf[LOWPASS_NUM_COEF];
  36     int32_t x[LOWPASS_NUM_COEF];
  37     int32_t y[LOWPASS_NUM_COEF];
  38 } lowpass_t;
  39
  40 void generateLowpassCoeffs2(int16_t freq, lowpass_t *filter);
  41 int32_t lowpassFixed(lowpass_t *filter, int32_t in, int16_t freq);