/*ADAPTTB.C - ADAPTIVE FILTER USING ASIN, ACOS TABLE*/
#define beta 0.005       /*rate of adaptation       */
#define N  30            /*order of filter          */
#define NS 128           /*number of samples        */
#define Fs 8000          /*sampling frequency       */
#define pi 3.1415926
#define inp 1000*sin(2*pi*T*1000/Fs)  /*input       */
#include "scdat"         /*table for asin, acos     */
#include "math.h"

main()
{
 int I, J, T, Y;
 double E, yo, xin, out_data;
 double W[N+1];
 double Delay[N+1];
 volatile int *IO_OUTPUT = (volatile int*) 0x809d00;
 yo=0;
 for (T=0; T < N; T++)
  {
   W[T] = 0.0;
   Delay[T] = 0.0;
  }
 for (T=0; T < NS; T++) /*# of output samples             */
  {
   xin = inp/1000;      /*scale for range between 1 and -1*/
   Y = ((xin)+1)*100;   /*step up array between 0 and 200 */
   if (yo > xin)        /*is signal falling or rising     */
    Delay[0] = yc[Y];   /*signal is falling, acos domain  */
   else                 /*otherwise                       */
    Delay[0] = ys[Y];   /*signal is rising, asin domain   */
   out_data = 0;        /*init filter output to zero      */
    yo = xin;           /*store input                     */
   for (I=0; I<=N; I++)
    out_data +=(W[I]*Delay[I]);     /*filter output       */
   E = xin - out_data;              /*error signal        */
   for (J=N; J > 0; J--)
    {
     W[J]=W[J]+(beta*E*Delay[J]);   /*update coefficients */
     if (J != 0)
     Delay[J] = Delay[J-1];         /*update data samples */
    }
   *IO_OUTPUT++ = out_data*1000;    /* output signal      */
  }
}