expfft01.c

这个是用DSP实现的FFT变换

extern void InitC5402(void);
extern void OpenMcBSP(void);
extern void CloseMcBSP(void);
extern void READAD50(void);
extern void WRITEAD50(void);

/***********************************************************************
** Main Function Program
***********************************************************************/
  #include "stdio.h"
  #include "math.h"
  
  void kfft(pr,pi,n,k,fr,fi,l,il)
  int n,k,l,il;
  double pr[],pi[],fr[],fi[];
  { int it,m,is,i,j,nv,l0;
    double p,q,s,vr,vi,poddr,poddi;
    for (it=0; it<=n-1; it++)
      { m=it; is=0;
        for (i=0; i<=k-1; i++)
          { j=m/2; is=2*is+(m-2*j); m=j;}
        fr[it]=pr[is]; fi[it]=pi[is];
      }
    pr[0]=1.0; pi[0]=0.0;
    p=6.283185306/(1.0*n);
    pr[1]=cos(p); pi[1]=-sin(p);
    if (l!=0) pi[1]=-pi[1];
    for (i=2; i<=n-1; i++)
      { p=pr[i-1]*pr[1]; q=pi[i-1]*pi[1];
        s=(pr[i-1]+pi[i-1])*(pr[1]+pi[1]);
        pr[i]=p-q; pi[i]=s-p-q;
      }
    for (it=0; it<=n-2; it=it+2)
      { vr=fr[it]; vi=fi[it];
        fr[it]=vr+fr[it+1]; fi[it]=vi+fi[it+1];
        fr[it+1]=vr-fr[it+1]; fi[it+1]=vi-fi[it+1];
      }
    m=n/2; nv=2;
    for (l0=k-2; l0>=0; l0--)
      { m=m/2; nv=2*nv;
        for (it=0; it<=(m-1)*nv; it=it+nv)
          for (j=0; j<=(nv/2)-1; j++)
            { p=pr[m*j]*fr[it+j+nv/2];
              q=pi[m*j]*fi[it+j+nv/2];
              s=pr[m*j]+pi[m*j];
              s=s*(fr[it+j+nv/2]+fi[it+j+nv/2]);
              poddr=p-q; poddi=s-p-q;
              fr[it+j+nv/2]=fr[it+j]-poddr;
              fi[it+j+nv/2]=fi[it+j]-poddi;
              fr[it+j]=fr[it+j]+poddr;
              fi[it+j]=fi[it+j]+poddi;
            }
      }
    if (l!=0)
      for (i=0; i<=n-1; i++)
        { fr[i]=fr[i]/(1.0*n);
          fi[i]=fi[i]/(1.0*n);
        }
    if (il!=0)
      for (i=0; i<=n-1; i++)
        { pr[i]=sqrt(fr[i]*fr[i]+fi[i]*fi[i]);
          if (fabs(fr[i])<0.000001*fabs(fi[i]))
            { if ((fi[i]*fr[i])>0) pi[i]=90.0;
              else pi[i]=-90.0;
            }
          else
            pi[i]=atan(fi[i]/fr[i])*360.0/6.283185306;
        }
   }

 
void main(void)
{
		int i,j,n,k=0;		
		double x[128],pr[128],pi[128],fr[128],fi[128],mo[128];
    	int xm,zm;
		int *px = (int*)0x3000;
		int *pz = (int*)0x3080;
		n=128;
	for (; ;)
	{
		InitC5402(); /* initialize C5402 DSP */
		OpenMcBSP();

//		for (;;)
		{	
		  for (j=0; j<=4; j++)
		  { 
			READAD50();
		
			px = (int*)0x3000;
			for (i=0; i<=n-1; i++)
			{
				xm=*px;
				x[i]=xm/32768.0;
				pr[i]=x[i];
				pi[i]=0;
				px++;
			}		
    	
			kfft(pr,pi,128,7,fr,fi,0,1);
    
			pz = (int*)0x3080;
			for (i=0;i<=n-1;i++)
	  		{
	       		mo[i] = sqrt(fr[i]*fr[i]+fi[i]*fi[i]);
		   		zm = (int)(mo[i]*1000.0);
		   		*pz = zm;
		   		pz++;
		  	}
		  	
		k++;
		WRITEAD50();
		
		}	
	}	
  }			
		/*void PROCESSING(void)
		{
		do the necessery operations here!*/
}

/***********************************************************************
** End of File –– exp08.c
***********************************************************************/