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dsp.c
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dsp.c
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/*
* Copyright (c) 2011, Regents of the University of California
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* - Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* - Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
* - Neither the name of the University of California, Berkeley nor the names
* of its contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
*
* Digital signal processing module
*
* by Stanley S. Baek
*
* v.alpha
*
* Revisions:
* Stanley S. Baek 2011-01-28 Initial release
*/
#include "dsp.h"
#include <stdlib.h>
/*-----------------------------------------------------------------------------
* Public functions
-----------------------------------------------------------------------------*/
float dspApplyFilter(DigitalFilter f, float x) {
int i;
//unsigned char idx = f->index;
float y = f->xcoef[0] * x;
for (i = 1; i <= f->order; ++i) {
y += f->xcoef[i]*f->xold[f->index] - f->ycoef[i]*f->yold[f->index];
f->index = (f->index == f->order-1)? 0 : f->index + 1;
}
f->index = (f->index == 0)? f->order - 1 : f->index - 1;
f->xold[f->index] = x;
f->yold[f->index] = y;
return y;
}
DigitalFilter dspCreateFilter(unsigned char order, FilterType type,
float* xcoeffs, float* ycoeffs) {
int i;
if (order == 0) return NULL;
DigitalFilter f = (DigitalFilter)malloc(sizeof(DigitalFilterStruct));
f->order = order;
f->type = type;
f->xcoef = (float*)malloc((order+1)*sizeof(float));
f->ycoef = (float*)malloc((order+1)*sizeof(float));
f->xold = (float*)malloc(order*sizeof(float));
f->yold = (float*)malloc(order*sizeof(float));
f->index = 0;
for(i = 0; i < order; ++i) {
f->xold[i] = 0;
f->yold[i] = 0;
f->xcoef[i] = xcoeffs[i];
f->ycoef[i] = ycoeffs[i];
}
f->xcoef[order] = xcoeffs[order];
f->ycoef[order] = ycoeffs[order];
return f;
}
float* dspGetOutputValues(DigitalFilter f) {
return f->yold;
}
float* dspGetInputValues(DigitalFilter f) {
return f->xold;
}
float dspGetLatestOutputValue(DigitalFilter f) {
return (f == NULL)? 0.0 : f->yold[f->index];
}
float dspGetLatestInputValue(DigitalFilter f) {
return (f == NULL)? 0.0 : f->xold[f->index];
}
unsigned char dspGetIndex(DigitalFilter f) {
return f->index;
}
void dspDeleteFilter(DigitalFilter f) {
free(f->xcoef);
free(f->ycoef);
free(f->xold);
free(f->yold);
free(f);
}