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

#include  
#include  
#define PI 3.1415926 
 
unsigned char i,w[32]; 
float dataR[]={5,5,5,5,0,0,0,0}; 
float dataI[]={0,0,0,0,0,0,0,0}; 
 
void FFT(float dataR[],float dataI[]) 
{ 
   int x0,x1,x2,xx; 
    
   int L,j,k,b,p; 
   float TR,TI,temp; 
 
/********** following code invert sequence ************/ 
 for(i=0;i<8;i++) 
  {  
   x0=x1=x2=0; 
   x0=i&0x01;  
   x1=(i/2)&0x01;  
   x2=(i/4)&0x01; 
   xx=x0*4+x1*2+x2; 
   dataI[xx]=dataR[i];   //实部的数放在虚部数组中 
  } 
 for(i=0;i<8;i++) 
  {  
   dataR[i]=dataI[i];    //将虚部保存的数传回实部 
   dataI[i]=0;  
  } 
/************** following code FFT *******************/ 
 for(L = 1 ; L <= 3 ; L ++ )            // for (1)  L 代表第几级 
  {  
    b = 1 ;  
    i = L - 1 ;           
    while ( i > 0 )           //计算第L层旋转因子的个数，即输入口间距 b= 2^(L-1)   
     { 
       b=b*2;  
       i--; 
     }                         
    
   for ( j = 0 ; j <= b - 1 ; j ++ )    // for (2)  j 用来控制计算第几个旋转因子 
    { 
       p = 1 ; 
       i = 3 - L ;      
        
      while ( i > 0 )                           /* p=pow(2,3-L)*j; */ 
         { 
          p = p * 2 ;  
          i -- ; 
         } 
      p=p*j; 
        
        for ( k = j ; k < 8 ; k = k + 2 * b )  /* for (3) */ 
           {  p=2*PI*p/8; 
              TR = dataR [ k ] ; 
              TI = dataI [ k ] ;  
              temp = dataR [ k + b ] ; 
              dataR[k]=dataR[k]+dataR[k+b]*cos(p)+dataI[k+b]*sin(p); 
              dataI[k]=dataI[k]-dataR[k+b]*sin(p)+dataI[k+b]*cos(p); 
              dataR[k+b]=TR-dataR[k+b]*cos(p)-dataI[k+b]*sin(p); 
              dataI[k+b]=TI+temp*sin(p)-dataI[k+b]*cos(p); 
			   
			   
			  /*dataR [ k ] = dataR [ k ] + dataR [ k + b ] * cos_tab [ p ] + dataI [ k + b ] * sin_tab [ p ] ; 
              dataI [ k ] = dataI [ k ] - dataR [ k + b ] * sin_tab [ p ] + dataI [ k + b ] * cos_tab [ p ] ; 
              dataR [ k + b ] = TR - dataR [ k + b ] * cos_tab [ p ] - dataI [ k + b ] * sin_tab [ p ] ; 
              dataI [ k + b ] = TI + temp * sin_tab [ p ] - dataI [ k + b ] * cos_tab [ 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 ; 
 
}  
 
void main() 
{ 
 FFT(dataR,dataI); 
 while(1); 
}