****************************************************************************
* (FFT.c FFT.h)
*
*
* 1.define a array which would contain the number you get from ADC
* like: // struct compx sample[16];
* and after that you will use this array for FFT.
* 2.you also must define a number used for times which you will
* operate papilionaceous(蝶形) operation.
* like: // unsigned char Mum = 16;//2exp(Num)
&
*attantion: * 基于时间抽取，同址计算
* * 要知道进行蝶形运算的数组必须是 2exp(Num)个
* * 数组的赋值是换算成的电压值,而不是采样后的寄存器结果
*
*made by: SuLi
*Version: 1.0
*Time: 07-8-29
*****************************************************************************/
#ifndef _FFT_h_
#define _FFT_h_
#include "math.h"
struct compx
{
float real;//实部
float imag;//虚部
};
extern void FFT(struct compx *xin, unsigned int Num);
#endif
/*
*
* 1.define a array which would contain the number you get from ADC
* like: // struct compx sample[16];
* and after that you will use this array for FFT.
* 2.you also must define a number used for times which you will
* operate papilionaceous(蝶形) operation.
* like: // unsigned char Mum = 16;//2exp(Num)
&
*attantion: * 基于时间抽取，同址计算
* * 要知道进行蝶形运算的数组必须是 2exp(Num)个
* * 数组的赋值是换算成的电压值,而不是采样后的寄存器结果
*
*made by: SuLi
*Version: 1.0
*Time: 07-8-29
*****************************************************************************/
#include "FFT.h"
/*
struct compx
{
float real;//实部
float imag;//虚部
}compx;*/
struct compx EE(struct compx b1,struct compx b2)//蝶形运算单元
{
struct compx b3;
b3.real=b1.real*b2.real-b1.imag*b2.imag;
b3.imag=b1.real*b2.imag+b1.imag*b2.real;
return(b3);
}
void FFT(struct compx *xin, unsigned int Num)
{
int f,m,LH,nm,i,k,j,L;
float p , ps;
int le,B,ip;
float pi;
struct compx w,t;
LH="Num/2"; //首先分为两组
f="Num"; //输入的数据个数
for(m=1;(f=f/2)!=1;m++){;} //m 表示将数据进行2分分组,f 不过是中间变量
//直到不能载分 也就是说 Num = 2exp(m)
nm="Num-2"; //
j="Num/2"; //
/*变址运算*/
for(i=1;i<=nm;i++)//i从 1--(Num-1) (去头去尾)//j=Num/2
{
if(i<j){t=xin[j];xin[j]=xin[i];xin[i]=t;}
k="LH";
while(j>=k){j=j-k;k=k/2;}
j="j"+k;
}
//**************蝶形运算的主程序*************
{
for(L=1;L<=m;L++)
{
le=(int)pow(2,L)+1;
B="le/2";
pi="3".14159;
for(j=0;j<=B-1;j++)
{
p="pow"(2,m-L)*j;
ps="2"*pi/Num*p;
w.real=cos(ps);
w.imag=-sin(ps);
for(i=j;i<=Num-1;i=i+le)
{
ip="i"+B;
t="EE"(xin[ip],w);
xin[ip].real=xin[i].real-t.real;
xin[ip].imag=xin[i].imag-t.imag;
xin[i].real=xin[i].real+t.real;
xin[i].imag=xin[i].imag+t.imag;
}
}
}
}
return ;
}
