dfilter_avg.c

/*
 * Copyright (c) 2012, 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.
 *
 *
 * Averaging filter using a circular buffer
 *
 * by Andrew Pullin
 *
 * v.0.1
 *
 * Revisions:
 *  Andrew Pullin   2012-5-28   Initial release.
 */

#include "dfilter_avg.h"
#include <stdlib.h>


///////////////   Public functions  //////////////////

void filterAvgCreate(filterAvgInt_t* filt, unsigned int length){
    filt->data = calloc(length, sizeof(int)); //Initialize data to 0
    filt->windowLen = length;
    filt->index = 0;
    filt->accum = 0;
}

void filterAvgUpdate(filterAvgInt_t* filt, int newval){
    // Add new value to accumulation, subtract existing value that is
    // going to be overwritten.
    filt->accum += newval - filt->data[filt->index];
    // Set new value
    filt->data[filt->index] = newval;
    // Circularly increment index
    filt->index = (filt->index + 1) % filt->windowLen;
}

// TODO (apullin) : more efficient calculation? DSP? delta?
int filterAvgCalc(filterAvgInt_t* filt){
    return (int)(filt->accum / (filt->windowLen));
}