数字电压表是怎么测量电压的?

设计图如下

源代码如下

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

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

#include "reg51.h"

sbit ST_ALE=P3^0;//START and ALE both connect to P3.0

sbit EOC=P3^1;//EOC connect to P3.1

sbit OE=P3^2;//OE conect to P3.2

sbit CLK=P3^3;//CLK connect to P3.3

unsigned char CHANNEL;//AD channel variable

unsigned char LED[10]={0x3F,0x06,0x5B,0x4F,0x66,0x6D,0x7D,0x07,0x7F,0x6F};

//common cathode LED code

unsigned char CHECK[4]={0xFE,0xFD,0xFB,0xF7};//choose LED channel

void delay(unsigned char time)

{

unsigned char i,j;

for(i=time;i>0;i--)

for(j=250;j>0;j--)

;

}

void display()

{

unsigned long temp;

unsigned char DATA,digit[4];

unsigned int k,l;

DATA=P1;//save AD data

temp=DATA;//the temporary variable

temp=temp*1000/51;//AD formula:D=A*5/255

digit[0]=temp/1000;//the thousands place

digit[1]=temp%1000/100; //the hundreds place

digit[2]=temp%1000%100/10; //the tens place

digit[3]=temp%1000%100%10;//the ones place

DATA=P2; //save P2

for(k=0;k<1000;k++)

{

/*lighten each LED and equal the below for loop

P1=LED[digit[0]]+0x80;

P2_4=0;

P2_4=1;

P1=LED[digit[1]];

P2_5=0;

P2_5=1;

P1=LED[digit[2]];

P2_6=0;

P2_6=1;

P1=LED[digit[3]];

P2_7=0;

P2_7=1;

*>

for(l=0;l<4;l++)

{

P2=P2|0x0F;//avoid LED residual

P0=LED[digit[l]]+0x80*(l==0);//LED code

P2=DATA&CHECK[l];//choose LED channel

}

}

P2=DATA;//restore P2

}

void main()

{

ST_ALE=0;//START and ALE default

OE=0;//OE default

TMOD=0x02;//T0 operate in mode 2

EA=1;//all interrupt enable

ET0=1;//T0 interrupt enable

TR0=1;//T0 run

while(1)

{

ST_ALE=1;//lock the AD channel address

ST_ALE=0;//AD run

while(EOC==0);//wait until AD over

OE=1;//enable to transmit AD data

display();//view the AD result and diaplay LED

}

}

void T1_TIME() interrupt 1 using 0

{

CLK=~CLK;//CLK 500 kHz

}

设计已经硬件实现了,但是数码管显示和滑动变阻器的数着完全不符,求大神帮助啊!