fft.c

基于TI tms320lf2407 DSP 的FFT算法（编译环境CCS2.20)

/*******************************************************************/
#include "exp1_2407.h"
#include "math.h"
/*******************************************************************/
		int px[128];
		int pz[128];		
void sys_ini()                  //系统初始化子程序
{
     asm(" setc INTM");         //禁止所有中断
     asm(" clrc SXM");          //抑制符号位扩展
     asm(" clrc OVM");          //累加器中结果正常溢出
     * SCSR1=0x81FE;            //配置时钟锁相为4倍频CLKOUT=4*7.3728=29.4912M,使能外部模块
     * WDCR=0x00EF;             //禁止看门狗
     //WSGR=0x0600;               //io、ram、program都设为0等待读写
     * IFR=0xFFFF;              //清除所有中断标志,"写1清0"
}

void adc_ini()                  //ADC初始化子程序
{    
     * ADCTRL1=0x25C0;          //仿真器挂起时,完成最后一次ad,start_stop运行模式,
                                //高中断优先级,双排序模式,禁用其他模式
     * ADCTRL2=0x0202;          //禁用中断模式，清中断标志
     * MAXCONV=0x0000;          //启用排序器1，最大转换数为1
     * CHSELSEQ1=0x0000;        //选择模拟输入通道为0通道
}

void read_ad()
{
     int a;
     * ADCTRL2|=0x2000;         //软件启动eoc1--ad转换器
     for(a=0;a<128;a++)
     {       
       px[a]=(* RESULT0>>6);    //读出ad结果
     }
     return;
}
      
interrupt void nothing()
{
     return;
}

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;
        }
   return;
   }
    
int main (void)
{
                int i,j,n,k=0;		
		double x[128],pr[128],pi[128],fr[128],fi[128],mo[128];
    	        int xm,zm;

		n=128;  
  sys_ini();
  adc_ini();
	for (;;)
	{	
		  for (j=0; j<=4; j++)
		  { 
            read_ad();		
			for (i=0; i<=n-1; i++)
			{
				xm=px[i];
				x[i]=xm/1023.0;
				pr[i]=x[i];
				pi[i]=0;
			}		
    	
			kfft(pr,pi,128,7,fr,fi,0,1);
			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[i] = zm;
		  	}  	
		        pz[0]=0;
		        k++;
		  }	
        }	 	
}