/*SINEC.C - REAL-TIME SINE GENERATION BY RECURSIVE EQUATION*/
#include "aiccomc.c"               /*AIC comm routines     */
#include "math.h"                  /*math library function */
#define sample_freq 10000          /*sample frequency      */
#define sine_freq 3000             /*desired frequency     */  
#define pi 3.14159                 /*constant pi           */  
int AICSEC[4] = {0x162C,0x1,0x3872,0x67}; /*AIC config data*/

void sinewave(float A, float B, float C)
{                        
 float y[3] = {0.0,0.0,0.0};          /*y[n] array         */
 float x[3] = {0.0,0.0,1.0};          /*x[n] array         */
 int n = 2, result;                   /*declare variables  */
 while(1)
  {                              
   TWAIT;
   y[n] = A*y[n-1] + B*y[n-2] + C*x[n-1];  /*determine y[n]*/ 
   result = (int)(y[n]*1000);    /*out y[n] scaled by 1000 */
   PBASE[0x48] = result << 2;    /*output to AIC           */
   y[n-2] = y[n-1];              /*shift y's back in array */
   y[n-1] = y[n];                                 
   x[n-2] = x[n-1];              /*shift x's back in array */
   x[n-1] = x[n]; 
   x[n] = 0.0;                   /*set future x's to 0     */
  } 
}                               

main()
{
 float Fs, Fosc, w, T, A, B, C;  /*declare variables       */
 AICSET();                       /*initialize AIC          */
 Fs = sample_freq;               /*get sampling frequency  */
 Fosc = sine_freq;               /*get oscillator frequency*/
 T = 1/Fs;                       /*determine sample period */
 w = 2*pi*Fosc;                  /*determine angular freq  */
 A = 2 * cos((w * T));           /*determine coefficient A */
 B = -1.0;                       /*coeff B is constant     */
 C = sin((w * T));               /*determine coefficient B */
   sinewave(A, B, C);            /*call sinewave function  */
}