FIR and IIR Filters with on and off Functionality By: Nitin Jalan For: Dr. V. Kepuska Subject: Microcomputer System 1

IIR Filter: High And Low Pass //Low pass filter IIR function void lowpassfilter_IIR(void) { float x = (float)(iChannel0LeftIn<<8); //shifts bits of the float x 8 bits to the left int s; for(s = 0; s <= 2; s++) //increments s from 0 to 2 lpd0[s] = x - (lpA1[s]*lpd1[s]) - (lpA2[s]*lpd2[s]); //delay equation x = (lpB2[s] * lpd2[s]) + (lpB1[s] * lpd1[s]) + (lpB0[s] * lpd0[s]); //output equation lpd2[s] = lpd1[s]; //shifts the delays each sampling lpd1[s] = lpd0[s]; } iChannel0LeftOut = ((int)x) >> 8; //shifts the output back 8 bits to the right

FIR FIltters: High Pass and Low PAss void highpassfilter_FIR(void) { x[n] = (fract16) (iChannel0RightIn>>8); //shifts the x[n] 8 bits to the right if (variables<1024) buffer[variables++]= x[n]; //Buffer } output = 0; //sets the output to 0 for(p=0; p<101; p++) output = add_fr1x16(output, mult_fr1x16(x[(n-p+101) %101],yhp[p])); //filter delay equation including circular buffer //uses fract16 funcions n++; //increment pointer n = n % 101; //keeps the pointer positive iChannel0RightOut=((int)(output))<<8; //Output is shifted back 8 bits to the left

References my.fit.edu/~vkepuska/ece3551 Christian Stumf and Ryan Boleman Lab