#include <reg52.h>
sbit     BMA    = P1^4;//編碼開關(guān)A引腳
sbit     BMB    = P1^5;//編碼開關(guān)B引腳
sbit     BMC    = P1^6;//編碼開關(guān) 下按引腳

unsigned char  display[3];
unsigned char  code  LEDData[ ] = { 
   0xC0,0xF9,0xA4,0xB0,0x99,0x92,
   0x82,0xF8,0x80,0x90,0xff
}; 
unsigned char  counter = 0;     //編碼器脈沖計(jì)數(shù) 
unsigned char  n,shift;

/**********************************************************

ms延時(shí)子函數(shù)

**********************************************************/
void delayms(unsigned int ms)
{
  unsigned char k;

  while (ms--)
  {
    for (k = 0; k < 114; k++)
      ;
  }
}

/**********************************************************

掃描編碼器子函數(shù)

在編碼器引腳A為低電平期間：

編碼器引腳B從0到1為正轉(zhuǎn)，編碼器引腳B從1到0為反轉(zhuǎn)。

**********************************************************/
void scan_encoder(void) 
{ 
   static  bit  Curr_b;  //定義一個(gè)變量來儲(chǔ)存當(dāng)前B信號(hào) 
   static  bit  Last_b;  //定義一個(gè)變量來儲(chǔ)存上次B腳信號(hào) 
   static  bit  update= 0;

   if( BMA && BMB)           //編碼器無轉(zhuǎn)動(dòng)退出
   {
     update = 0; 
     return;
   }

   Last_b = BMB;       //記錄B信號(hào)

   while(!BMA)                //等待A由低變高
   { 
     Curr_b = BMB;     //記錄等待期間的B信號(hào)(指當(dāng)前B信號(hào))
     update = 1;
   
   	if(!BMC)                //當(dāng)按下旋鈕時(shí)
     {
       counter = 0;            //計(jì)數(shù)單元清零(歸位)
       delayms(10);
     }
   
   
   } 

   if(update)
   {
   update = 0 ;
     if( (Last_b == 0)&&(Curr_b== 1) ) //B從0到1為正轉(zhuǎn)
     { 
   if(counter == 255)
       return;
       counter++;          //正轉(zhuǎn)計(jì)數(shù)加
     } 
     else if( (Last_b == 1)&&(Curr_b == 0) ) //B從1到0為反轉(zhuǎn)
     { 
       if(counter == 0)
       return;
       counter--;         //反轉(zhuǎn)計(jì)數(shù)減
     } 
   }
}

/**********************************************************

主函數(shù)

**********************************************************/
void  main(void)
{
   P0 = 0xff;
   P1 = 0xff;
   P2 = 0xff;

   T2CON = 0x00;               //設(shè)置T2CON寄存器         
   TH2 = 0xfc;                 //1ms定時(shí)
   TL2 = 0x66;
   ET2 = 1;                    //啟用Timer2中斷
   EA = 1;                     //總中斷允許
   TR2 = 1;                    //啟動(dòng)定時(shí)器2
   counter = 0;                //計(jì)數(shù)單元清零

   while(1)
   {

   scan_encoder();
    if(!BMC)                //當(dāng)按下旋鈕時(shí)
     {
       counter = 0;            //計(jì)數(shù)單元清零(歸位)
       delayms(10);
     } 
   }
}

/*********************************************************

Timer2中斷函數(shù)

**********************************************************/
void  timer2() interrupt 5 
{ 
   TR2 = 0;
   TF2 = 0;                         //手工清中斷標(biāo)志  
   TH2 = 0xfc;                      //1ms定時(shí)常數(shù)
   TL2 = 0x66;

   if(n >= 3)                       //3位數(shù)碼管顯示
   {
     n = 0;
     shift = 0x7f;                  //送位碼初值
     P2 = 0xff;                     //關(guān)閉顯示
   }
   else
   {
     display[0] = counter%10;       //個(gè)位數(shù)據(jù)
     display[1] = (counter%100)/10; //十位數(shù)據(jù)
     display[2] = counter/100;      //百位數(shù)據(jù)
     
     if(display[2] == 0)
     {
       display[2] = 0x0a;           //百位為0,不顯示
       if(display[1] == 0)
       display[1]  =0x0a;           //十位為0,不顯示
}

     P0 = LEDData[display[n++]];    //送段碼
     P2 = shift;                    //送位碼
     shift = (shift>>1)|0x80;       //調(diào)整位碼
   }
   TR2 = 1;
}

/*********************************************************/