51做FFT有些困难，可以使用增强型（RAM）的51机子进行

参考程序：

#include<STC12C5A.H>

#define uchar unsigned char

#define uint unsigned int

#define channel 0x01 //设置AD通道为 P1.1

//---------------------------------------------------------------------

sbit SDA_R=P1^2;

sbit SDA_R_TOP=P1^3;

sbit SDA_G=P1^4;

sbit SDA_G_TOP=P1^5;

sbit STCP=P1^6;

sbit SHCP=P1^7;

//---------------------------------------------------------------------

//----------------------------------------------------------------------------------------------------------------------

//放大128倍后的sin整数表（128）

code char SIN_TAB[128] = { 0, 6, 12, 18, 24, 30, 36, 42, 48, 54, 59, 65, 70, 75, 80, 85, 89, 94, 98, 102,

105, 108, 112, 114, 117, 119, 121, 123, 124, 125, 126, 126, 126, 126, 126, 125, 124, 123, 121, 119, 117, 114, 112,

108, 105, 102, 98, 94, 89, 85, 80, 75, 70, 65, 59, 54, 48, 42, 36, 30, 24, 18, 12, 6, 0, -6, -12, -18, -24, -30,

-36, -42, -48, -54, -59, -65, -70, -75, -80, -85, -89, -94, -98, -102, -105, -108, -112, -114, -117, -119, -121,

-123, -124, -125, -126, -126, -126, -126, -126, -125, -124, -123, -121, -119, -117, -114, -112, -108, -105, -102,

-98, -94, -89, -85, -80, -75, -70, -65, -59, -54, -48, -42, -36, -30, -24, -18, -12, -6 };

//放大128倍后的cos整数表（128）

code char COS_TAB[128] = { 127, 126, 126, 125, 124, 123, 121, 119, 117, 114, 112, 108, 105, 102, 98, 94,