#include <stdio.h> #include <math.h> #include "defs.h" #include "filter.h" Filter::Filter(int ord, Float gainAtDC, Float *ycs) { order = ord; dcGain = gainAtDC; dcGainInv = 1.0/gainAtDC; // Load coefficients based on order switch (ord) { case 9: ycoeff8 = ycs[8]; case 8: ycoeff7 = ycs[7]; case 7: ycoeff6 = ycs[6]; case 6: ycoeff5 = ycs[5]; case 5: ycoeff4 = ycs[4]; case 4: ycoeff3 = ycs[3]; case 3: ycoeff2 = ycs[2]; case 2: ycoeff1 = ycs[1]; case 1: ycoeff0 = ycs[0]; } // Choose iterate function switch (ord) { case 1: iterateFunc = iterate1; break; case 2: iterateFunc = iterate2; break; case 3: iterateFunc = iterate3; break; default: printf("Filter order %d not supported\n"); break; } // Start filters at 0 xval0 = xval1 = xval2 = xval3 = xval4 = xval5 = xval6 = xval7 = xval8 = xval9 = 0.0; yval0 = yval1 = yval2 = yval3 = yval4 = yval5 = yval6 = yval7 = yval8 = yval9 = 0.0; } void Filter::iterate(Float *in, Float *out, int n) { iterateFunc(this, in, out, n); } // First order iterator void Filter::iterate1(Filter *thisPtr, Float *in, Float *out, int n) { register Float x0, x1, y0, y1; // Restore state x1 = thisPtr->xval1; y1 = thisPtr->yval1; // Get coefficient(s) Float c0 = thisPtr->ycoeff0; Float gaininv = thisPtr->dcGainInv; // Recurrance relation y[n] = x[n-1] + x[n] + (ycoeff * y[n-1]) for (int i = 0; i < n; i++) { // shift x0 = x1; x1 = *in++; // shift y0 = y1; y1 = (x0 + x1) + (y0*c0); *out++ = gaininv * y1; // unity gain } // Save state thisPtr->xval1 = x1; thisPtr->yval1 = y1; } // Second order iterator void Filter::iterate2(Filter *thisPtr, Float *in, Float *out, int n) { register Float x0, x1, x2, y0, y1, y2; // Restore state x1 = thisPtr->xval1; x2 = thisPtr->xval2; y1 = thisPtr->yval1; y2 = thisPtr->yval2; // Get coefficient(s) Float c0 = thisPtr->ycoeff0, c1 = thisPtr->ycoeff1, gaininv = thisPtr->dcGainInv; // Recurrance relation // y[n] = x[n-2] + 2x[n-1] + x[n] + (yc0 * y[n-2] + yc1*y[n-1]) for (int i = 0; i < n; i++) { // shift x0 = x1; x1 = x2; x2 = *in++; // shift y0 = y1; y1 = y2; y2 = (x0 + 2.0*x1 + x2) + (c0*y0 + c1*y1 ); *out++ = gaininv * y2; // unity gain } // Save state thisPtr->xval1 = x1; thisPtr->xval2 = x2; thisPtr->yval1 = y1; thisPtr->yval2 = y2; } // Third order iterator void Filter::iterate3(Filter *thisPtr, Float *in, Float *out, int n) { register Float x0, x1, x2, x3, y0, y1, y2, y3; // Restore state x1 = thisPtr->xval1; x2 = thisPtr->xval2; x3 = thisPtr->xval3; y1 = thisPtr->yval1; y2 = thisPtr->yval2; y3 = thisPtr->yval3; // Get coefficient(s) Float c0 = thisPtr->ycoeff0, c1 = thisPtr->ycoeff1, c2 = thisPtr->ycoeff2, gaininv = thisPtr->dcGainInv; // Recurrance relation // y[n] = 1*x[n-3] // + 3*x[n-2] // + 3*x[n-1] // + 1*x[n] // + yc0 * y[n-3] // + yc1 * y[n-2] // + yc2 * y[n-1]) for (int i = 0; i < n; i++) { // shift x0 = x1; x1 = x2; x2 = x3; x3 = *in++; // shift y0 = y1; y1 = y2; y2 = y3; y3 = (x0 + 3.0*(x1 + x2) + x3) + (c0*y0 + c1*y1 + c2*y2); *out++ = gaininv * y3; // unity gain } // Save state thisPtr->xval1 = x1; thisPtr->xval2 = x2; thisPtr->xval3 = x3; thisPtr->yval1 = y1; thisPtr->yval2 = y2; thisPtr->yval3 = y3; }
file: /Techref/uk/ac/york/cs/www-users/http/~fisher/software/mkfilter/odds/jim_miller/filter.c++, 3KB, , updated: 2000/4/4 11:49, local time: 2024/6/17 05:39,
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