kopia lustrzana https://github.com/xaelsouth/rtl-wmbus
134 wiersze
3.2 KiB
C
134 wiersze
3.2 KiB
C
#ifndef FIR_H
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#define FIR_H
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/*-
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* Copyright (c) 2017 <xael.south@yandex.com>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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/*
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* Floating and fixed point implementations of Finite Response Filter.
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*/
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#include <stdint.h>
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#include <stddef.h>
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#include <fixedptc/fixedptc.h>
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typedef struct
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{
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const size_t length;
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float *const b;
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size_t i;
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float *hist;
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} FIRF_FILTER;
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float firf(float sample, FIRF_FILTER *filter);
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float firf(float sample, FIRF_FILTER *filter)
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{
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const float *b = filter->b;
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float *hist = &filter->hist[filter->i++];
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size_t i;
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*hist = sample;
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sample = 0; // will be "y"
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for (i = filter->i; i--;)
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{
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sample += *b++ * *hist--;
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}
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hist = &filter->hist[filter->length-1];
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for (i = filter->length; i-- > filter->i;)
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{
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sample += *b++ * *hist--;
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}
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if (filter->i >= filter->length) filter->i = 0;
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return sample;
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}
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void firf_lms(float mu_e, FIRF_FILTER *filter)
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{
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float *b = &filter->b[filter->length-1];
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size_t i;
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float *hist;
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i = filter->i;
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hist = &filter->hist[i];
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while (i++ < filter->length)
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{
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*b-- += mu_e * *hist++;
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}
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i = 0;
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hist = &filter->hist[i];
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while (i++ < filter->i)
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{
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*b-- += mu_e * *hist++;
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}
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}
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typedef struct
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{
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const size_t length;
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const fixedpt *const b;
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size_t i;
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fixedpt *hist;
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} FIRFP_FILTER;
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fixedpt firfp(fixedpt sample, FIRFP_FILTER *filter);
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fixedpt firfp(fixedpt sample, FIRFP_FILTER *filter)
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{
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const fixedpt *b = filter->b;
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fixedpt *hist = &filter->hist[filter->i++];
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size_t i;
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*hist = sample;
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sample = 0; // will be "y"
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for (i = filter->i; i--;)
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{
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sample = fixedpt_add(sample, fixedpt_mul((*b++), (*hist--)));
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}
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hist = &filter->hist[filter->length-1];
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for (i = filter->length; i-- > filter->i;)
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{
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sample = fixedpt_add(sample, fixedpt_mul((*b++), (*hist--)));
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}
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if (filter->i >= filter->length) filter->i = 0;
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return sample;
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}
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#endif /* FIR_H */
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