//MCU:AT89S51
//晶振：12M
//采用查詢方式讀AD轉換后的值
#include "AT89X51.H"
#include "math.h"
#include "intrins.h"
unsigned char code numcode[]={ 0xc0,0xf9,0xa4,0xb0,0x99,
                               0x92,0x82,0xf8,0x80,0x90,
							   0xC1,0XB7,0xFF
							  };//數(shù)字0～9及"U="”“共陽數(shù)碼管代碼 
unsigned char code dot_numcode[]={0X40,0X79,0X24,0X30,0X19,
                                  0X12,0X02,0X78,0X00,0X10
								 };//帶數(shù)點的0～9共陽數(shù)碼管代碼

unsigned char code bitcode[]={0xfe,0xfd,0xfb,0xf7,
                              0xef,0xdf,0xbf,0x7f}; //數(shù)碼管位選代碼
unsigned char dispbuff[8]={0,0,0,11,10,12,12,12};
unsigned char disp_count;
unsigned char flag=1;
unsigned char flag_count;
unsigned long int getdata;
 
sbit START=P3^0;
sbit EOC=P3^2;
sbit OE=P3^1;
sbit AD_ALE=P3^3;

 
void main(void)
{


  TMOD=0x01;   //選擇定時器T0，方式為1（16位定時器）
  TH0=(65536-3000)/256;  //定時3MS初值
  TL0=(65536-3000)%256;
  TR0=1;
  ET0=1;
  EA=1;
  AD_ALE=0;
  START=0;
  OE=0;
  while(1)
    {

   if(flag==1)  //每隔40ms啟動一次AD采樣

    { 
    flag=0;
	AD_ALE=1; //鎖存輸入通道
	START=0;     //驅動AD轉換
    START=1;
	AD_ALE=0;
    START=0;      //保持低電平
	while(EOC==0); //等待AD轉換結束
    TR0=0;         //AD轉換結束時先停止T0
    P0=0XFF;      //關閉數(shù)碼管顯示，呵呵，其實人眼是感覺不到數(shù)碼管熄滅的
	P1=0XFF;     // 這個很重要
	OE=1;        //轉換結束，允許AD值輸出
    getdata=P1;  //讀出AD值，如果硬件連接上改成P2口來讀AD值，這句就改成"getdata=P2;"
    OE=0;        //禁止輸出
	getdata=(unsigned long int)((unsigned long int)(getdata*500)/255);//轉換成電壓 
    dispbuff[2]=getdata/100;  
    dispbuff[1]=(getdata%100)/10;
    dispbuff[0]=getdata%10;
    TR0=1;   //重新啟動T0
    }
	}
}
 
void t0(void) interrupt 1
{
 
  TH0=(65536-3000)/256;
  TL0=(65536-3000)%256;

  if(disp_count==2)
    P0=dot_numcode[dispbuff[disp_count]];
  else
    P0=numcode[dispbuff[disp_count]];
  P1=bitcode[disp_count];
  disp_count++;
  flag_count++;
  if(disp_count==8)
    {
      disp_count=0;
	}
  if(flag_count==100)
    {
	 flag=1;
	 flag_count=0;
	}
}