如何用51單片機實現音頻信號的頻譜顯示（在LCD上顯示）

51做FFT有些困難，可以使用增強型（RAM）的51機子進行參考程序：#include<STC12C5A.H>

#define uchar unsigned char

#define uint unsigned int

#define channel 0x01 //設置AD通道為 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倍後的sin整數表（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倍後的cos整數表（128）

code char COS_TAB[128] = { 127, 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, 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 };//采樣存儲序列表

code char LIST_TAB[128] = { 0, 64, 32, 96, 16, 80, 48, 112,

8, 72, 40, 104, 24, 88, 56, 120,

4, 68, 36, 100, 20, 84, 52, 116,

12, 76, 44, 108, 28, 92, 60, 124,

2, 66, 34, 98, 18, 82, 50, 114,

10, 74, 42, 106, 26, 90, 58, 122,

6, 70, 38, 102, 22, 86, 54, 118,

14, 78, 46, 110, 30, 94, 62, 126,

1, 65, 33, 97, 17, 81, 49, 113,

9, 73, 41, 105, 25, 89, 57, 121,

5, 69, 37, 101, 21, 85, 53, 117,

13, 77, 45, 109, 29, 93, 61, 125,

3, 67, 35, 99, 19, 83, 51, 115,

11, 75, 43, 107, 27, 91, 59, 123,

7, 71, 39, 103, 23, 87, 55, 119,

15, 79, 47, 111, 31, 95, 63, 127

};

uchar COUNT=0,COUNT1=0,ADC_Count=0,LINE=15,G,T;

uchar i,j,k,b,p;

int Temp_Real,Temp_Imag,temp; // 中間臨時變量

uint TEMP1;

int xdata Fft_Real[128];

int xdata Fft_Image[128]; // fft的虛部

uchar xdata LED_TAB2[64]; //記錄漂浮物是否需要停頓壹下

uchar xdata LED_TAB[64]; //記錄紅色柱狀

uchar xdata LED_TAB1[64]; //記錄漂浮點

void Delay(uint a)

{

while(a--);

}void FFT()

{ //uchar X;

for( i=1; i<=7; i++) /* for(1) */

{

b=1;

b <<=(i-1); //碟式運算，用於計算隔多少行計算例如第壹極 1和2行計算，，第二級

for( j=0; j<=b-1; j++) /* for (2) */

{

p=1;

p <<= (7-i);

p = p*j;

for( k=j; k<128; k=k+2*b) /* for (3) 基二fft */

{

Temp_Real = Fft_Real[k]; Temp_Imag = Fft_Image[k]; temp = Fft_Real[k+b];

Fft_Real[k] = Fft_Real[k] + ((Fft_Real[k+b]*COS_TAB[p])>>7) + ((Fft_Image[k+b]*SIN_TAB[p])>>7);

Fft_Image[k] = Fft_Image[k] - ((Fft_Real[k+b]*SIN_TAB[p])>>7) + ((Fft_Image[k+b]*COS_TAB[p])>>7);

Fft_Real[k+b] = Temp_Real - ((Fft_Real[k+b]*COS_TAB[p])>>7) - ((Fft_Image[k+b]*SIN_TAB[p])>>7);

Fft_Image[k+b] = Temp_Imag + ((temp*SIN_TAB[p])>>7) - ((Fft_Image[k+b]*COS_TAB[p])>>7);

// 移位.防止溢出. 結果已經是本值的 1/64

Fft_Real[k] >>= 1;

Fft_Image[k] >>= 1;

Fft_Real[k+b] >>= 1;

Fft_Image[k+b] >>= 1;

}

// X=((((Fft_Real[1]* Fft_Real[1]))+((Fft_Image[1]*Fft_Image[1])))>>7);

Fft_Real[0]=Fft_Image[0]=0; //去掉直流分量

// Fft_Real[63]=Fft_Image[63]=0;

for(j=0;j<64;j++)

{

TEMP1=((((Fft_Real[j]* Fft_Real[j]))+((Fft_Image[j]*Fft_Image[j])))>>1);//求功率

if(TEMP1>1)TEMP1--;

else TEMP1=0;

if(TEMP1>31)TEMP1=31;

if(TEMP1>(LED_TAB[j]))LED_TAB[j]=TEMP1;

if(TEMP1>(LED_TAB1[j]))

{ LED_TAB1[j]=TEMP1;

LED_TAB2[j]=18; //提頓速度=12

}

}void Init()

{

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

P1ASF = 0x02; //0000,0010, 將 P1.1 置成模擬口

AUXR1 &=0xFB; //1111,1011, 令 ADRJ=0

EADC=1; //AD中斷打開

ADC_CONTR = ADC_POWER | ADC_SPEEDHH | ADC_START | channel;

//1110 1001 1打開 A/D （ADC_POWER）轉換電源；11速度為70周期壹次；

//0中斷標誌清零；1啟動adc(ADC_START);001AD通道打開（這裏為P1.1）;

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

P2M0=1;

P0M0=1;

TMOD=0X12;

TH0=0x30; //大約20K的采樣率（要完整頻段需40K以上。但音頻中10k以下居多，故本人選擇20K采樣，美觀些）

TL0=0x30;

TH1=0xEE;

TL1=0XC0;

ET0=1; //定時器0 打開

TR0=0; //關閉定時器

ET1=1;

TR1=1;

PT1=0;

PT0=1;

IPH=PADCH;

IP=PADC; //中斷優先級

EA=1; //總中斷打開

}

void ADC_Finish() interrupt 5

{ ADC_CONTR &= !ADC_FLAG;

Fft_Real[LIST_TAB[ADC_Count]]=(int)((ADC_RES)<<1)+(ADC_RESL>>1)-256;//-512; //按LIST_TAB表裏的順序，進行存儲采樣值,,

// ADC_CONTR = ADC_POWER | ADC_SPEEDHH| ADC_START | channel; // 為了采集負電壓，采用偏置采集。電壓提高到1/2 vcc，，所以要減去256

if(ADC_Count<=127)ADC_Count++;

else {EADC=0;TR0=0;}

} void LED_Display() interrupt 3 //中斷壹次顯示壹行。。。

{

TH1=0xF3;

TL1=0X00;

for (G=0;G<64;G++) //往點陣屏填充壹行的數據

{

if(LED_TAB[G]<=LINE+16)SDA_R_TOP=1;

else SDA_R_TOP=0;

if(LED_TAB[G]<=LINE)SDA_R=1;

else SDA_R=0; if(LED_TAB1[G]==LINE){SDA_G_TOP=1;SDA_G=0;}

else if(LED_TAB1[G]==(LINE+16)){SDA_G_TOP=0;SDA_G=1;}

else SDA_G=SDA_G_TOP=1;

SHCP=1;SHCP=0;

}

STCP=1;STCP=0;

P2=15-LINE;

if(LINE>0)LINE--;

else LINE=15;

//////////////////////////

if(LED_TAB[COUNT]>0)LED_TAB[COUNT]--; //柱狀遞減，

COUNT++;