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38 lines
979 B
C
38 lines
979 B
C
// fir.C
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// David_Harris@hmc.edu 25 December 2021
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// Finite Impulse Response Filter
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#include <math.h>
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#define N 2000
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#define M 100
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#define PI 3.14159
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double fir(double a[], double c[], double y[], int N, int M) {
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int i, j
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for (i=0; i<N-M; i++) {
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y[i] = 0;
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for (j=0; j<M; j++) {
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y[i] += c[j] * a[M+i-j];
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}
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}
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}
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int main(void) {
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double a[N], c[M], y[N-M];
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int i;
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// // step input with overlying high frequency sinusoid
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for (i=0; i<N; i++) a[i] = (i < N/2) + 0.5 * cos(2*PI*i/50);
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// filter coeffieints: replace with a sinc function with sharper response
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//for (i=0; i<M; i++) c[i] = 1.0/M; // low pass filter with equal coefficients
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for (i=0; i<M; i++) c[i] = 2.0*B*(sin(2.0*B*i/10)/(2.0*B*i/10)); // low pass filter with equal coefficients
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// inline assembly to measure time, with macro
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fir(a, c, y, N, M);
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// measure time again
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// *** generate signature
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// *** write_tohost
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} |