/*ADAPTDMV.C - ADAPTIVE FILTER FOR NOISE CANCELLATION     */
#include "math.h"
#define beta 1.5E-8            /*rate of convergence      */   
#define N 30                   /*# of coefficients        */
#define NS 128                 /*# of output sample points*/
#define Fs  8000               /*sampling frequency       */
#define pi  3.1415926
#define DESIRED 1000*sin(2*pi*T*1000/Fs) /*desired signal */
#define ADDNOISE 1000*sin(2*pi*T*312/Fs) /*additive noise */
#define REFNOISE 1000*cos(2*pi*T*312/Fs) /*reference noise*/
main()
{
 int I,T;
 float Y, E, DPLUSN;
 float W[N+1];
 float Delay[N+1];
 volatile int *IO_OUTPUT= (volatile int*) 0x809d00; 
 volatile int *IO_INPUT = (volatile int*) 0x809d80;
 for (T = 0; T < N; T++)
  {
    W[T] = 0.0;
    Delay[T] = 0.0;
  } 
 for (T=0; T < NS; T++)          /*# of output samples    */
  {  
    Delay[0] = REFNOISE;         /*adaptive filter's input*/
    DPLUSN = DESIRED + ADDNOISE; /*desired + noise, d+n   */
    Y = 0;                           
    for (I = 0; I < N; I++)
      Y += (W[I] * Delay[I]);    /*adaptive filter output */             
    E = DPLUSN - Y;              /*error signal           */               
    for (I = N; I > 0; I--)         
    {
      W[I] = W[I] + (beta*E*Delay[I]); /*update weights   */ 
      if (I != 0)                     
      Delay[I] = Delay[I-1];           /*update samples   */   
    } 
    *IO_OUTPUT++ = E;                  /*overall output E */          
    *IO_INPUT++ = DPLUSN;              /* store d + n     */
  }   
}