www.pudn.com > fft_iccavr.rar > fffff.c

#include  
#include  
#define PI 3.1415926 
#define qq PI/8 
 
int dataR[]={5,5,5,5,0,0,0,0,5,5,5,5,0,0,0,0}; 
int dataI[16],w[32]; 
 
 
void FFT(int dataR[],int dataI[]) 
{int x0,x1,x2,x3,x4,x5,x6,xx; 
 unsigned char i; 
 int L,j,k,b,p; 
 float TR,TI,temp; 
/********** following code invert sequence ************/ 
for(i=0;i<16;i++) 
{ x0=x1=x2=x3=x4=x5=x6=0; 
x0=i&0x01; x1=(i>>1)&0x01; x2=(i>>2)&0x01; x3=(i>>3)&0x01; 
//x4=(i>>4)&0x01; x5=(i>>5)&0x01; x6=(i>>6)&0x01; 
xx=x0*8+x1*4+x2*2+x3; 
dataI[xx]=dataR[i]; 
} 
for(i=0;i<16;i++) 
{ dataR[i]=dataI[i]; dataI[i]=0; } 
/************** following code FFT *******************/ 
for(L=1;L<=4;L++) { /* for(1) */ 
b=1; i=L-1; 
while(i>0)  
{b=b*2; i--;} /* b= 2^(L-1) */ 
for(j=0;j<=b-1;j++) /* for (2) */ 
{ p=1; i=4-L; 
while(i>0) /* p=pow(2,7-L)*j; */ 
{p=p*2; i--;} 
p=p*j;for(k=j;k<16;k=k+2*b) /* for (3) */ 
{ TR=dataR[k]; TI=dataI[k]; temp=dataR[k+b]; 
dataR[k]=dataR[k]+dataR[k+b]*cos(qq*p)+dataI[k+b]*sin(qq*p); 
dataI[k]=dataI[k]-dataR[k+b]*sin(qq*p)+dataI[k+b]*cos(qq*p); 
dataR[k+b]=TR-dataR[k+b]*cos(qq*p)-dataI[k+b]*sin(qq*p); 
dataI[k+b]=TI+temp*sin(qq*p)-dataI[k+b]*cos(qq*p); 
} /* END for (3) */ 
} /* END for (2) */ 
} /* END for (1) */ 
for(i=0;i<32;i++) 
  {                        /* 只需要32次以下的谐波进行分析 */ 
w[i]=sqrt(dataR[i]*dataR[i]+dataI[i]*dataI[i]); 
   if(!i) 
   { 
    w[i]=w[i]/64; 
   } 
  } 
w[0]=w[0]/2; 
} /* END FFT */ 
 
void main () 
  { 
    FFT(dataR,dataI); 
	while(1); 
  }