LCOV - code coverage report
Current view: top level - header/processing - iir_filter.h (source / functions) Hit Total Coverage
Test: trace.info Lines: 10 10 100.0 %
Date: 2023-02-20 11:47:18 Functions: 0 0 -

          Line data    Source code
       1             : /*------------------------------------------------------------------------------
       2             : --  Solar Orbiter's Low Frequency Receiver Flight Software (LFR FSW),
       3             : --  This file is a part of the LFR FSW
       4             : --  Copyright (C) 2021, Plasma Physics Laboratory - CNRS
       5             : --
       6             : --  This program is free software; you can redistribute it and/or modify
       7             : --  it under the terms of the GNU General Public License as published by
       8             : --  the Free Software Foundation; either version 2 of the License, or
       9             : --  (at your option) any later version.
      10             : --
      11             : --  This program is distributed in the hope that it will be useful,
      12             : --  but WITHOUT ANY WARRANTY; without even the implied warranty of
      13             : --  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
      14             : --  GNU General Public License for more details.
      15             : --
      16             : --  You should have received a copy of the GNU General Public License
      17             : --  along with this program; if not, write to the Free Software
      18             : --  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
      19             : -------------------------------------------------------------------------------*/
      20             : /*--                  Author : Alexis Jeandet
      21             : --                   Contact : Alexis Jeandet
      22             : --                      Mail : alexis.jeandet@lpp.polytechnique.fr
      23             : ----------------------------------------------------------------------------*/
      24             : #pragma once
      25             : #include <stdint.h>
      26             : 
      27             : #ifdef __cplusplus
      28             : extern "C"
      29             : {
      30             : #endif
      31             : 
      32             : #define B00 196
      33             : #define B01 196
      34             : #define B02 0
      35             : #define B10 131
      36             : #define B11 -244
      37             : #define B12 131
      38             : #define B20 161
      39             : #define B21 -314
      40             : #define B22 161
      41             : 
      42             : #define A00 1
      43             : #define A01 -925
      44             : #define A02 0
      45             : #define A10 1
      46             : #define A11 -947
      47             : #define A12 439
      48             : #define A20 1
      49             : #define A21 -993
      50             : #define A22 486
      51             : 
      52             : #define GAIN_B0 12
      53             : #define GAIN_B1 11
      54             : #define GAIN_B2 10
      55             : 
      56             : #define GAIN_A0 10
      57             : #define GAIN_A1 9
      58             : #define GAIN_A2 9
      59             : 
      60             : #define NB_COEFFS 3
      61             : #define COEFF0    0
      62             : #define COEFF1    1
      63             : #define COEFF2    2
      64             : 
      65             : 
      66             :     typedef struct filter_ctx
      67             :     {
      68             :         int W[NB_COEFFS][NB_COEFFS];
      69             :     } filter_ctx;
      70             : 
      71             : 
      72             :     /**
      73             :      * @brief filter is a Direct-Form-II filter implementation, mostly used to filter electric field
      74             :      * for HK
      75             :      * @param x, new sample
      76             :      * @param ctx, filter context, used to store previous input and output samples
      77             :      * @return a new filtered sample
      78             :      */
      79             :     static inline int filter(int x, filter_ctx* ctx)
      80             :     {
      81             :         static const int b[NB_COEFFS][NB_COEFFS]
      82             :             = { { B00, B01, B02 }, { B10, B11, B12 }, { B20, B21, B22 } };
      83             :         static const int a[NB_COEFFS][NB_COEFFS]
      84             :             = { { A00, A01, A02 }, { A10, A11, A12 }, { A20, A21, A22 } };
      85             :         static const int b_gain[NB_COEFFS] = { GAIN_B0, GAIN_B1, GAIN_B2 };
      86             :         static const int a_gain[NB_COEFFS] = { GAIN_A0, GAIN_A1, GAIN_A2 };
      87             : 
      88             :         // Direct-Form-II
      89      110940 :         for (int i = 0; i < NB_COEFFS; i++)
      90             :         {
      91       83205 :             x = x << a_gain[i];
      92             :             int32_t W
      93       83205 :                 = (x - (a[i][COEFF1] * ctx->W[i][COEFF0]) - (a[i][COEFF2] * ctx->W[i][COEFF1]))
      94       83205 :                 >> a_gain[i];
      95      332820 :             x = (b[i][COEFF0] * W) + (b[i][COEFF1] * ctx->W[i][COEFF0])
      96      249615 :                 + (b[i][COEFF2] * ctx->W[i][COEFF1]);
      97       83205 :             x = x >> b_gain[i];
      98       83205 :             ctx->W[i][1] = ctx->W[i][0];
      99       83205 :             ctx->W[i][0] = W;
     100             :         }
     101       27735 :         return x;
     102             :     }
     103             : 
     104             : #ifdef __cplusplus
     105             : }
     106             : #endif

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