原创 51单片机复习札记之四——按键

独立按键

我的开发板上独立按键有4个，分别是接在P3.2~P3.5上，当有键按下时，该端口被拉到低电平。按键在使用时会产生机械抖动，这里采用软件延时的方法去除抖动。

下面的程序是扫描接到P3.2上的按键，即S15，每按一次，数码管第一位从F开始减一递减，当减到0时，再回到F。

#include <reg52.h>

#include "Config.h"

//数码管段选和位选信号

sbit Seg = P2^6;

sbit Bit = P2^7;

//数码管0~F字形码

code uchar LED[] = {0x7B,0x42,0x1F,0x4F,0x66,0x6D,0x7D,0x43,

                            //     0  
1   2   3   
4    5    6   
7                                                                           0x7F,0x6F,0x77,0x7C,0x39,0x5E,0x3D,0x35};

                            //    8    9   A    B   
C   D   E   F

uchar c = 0;    //全局变量

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

函数名称：Delay

函数功能：延时

入口参数：uint t—要延时的毫秒数

返回参数：无

备    注：无

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

void Delay(uint t)

{

       uint
i;

       while(t--)

       {

              for
(i=0;i<125;i++)

              {}

       }

}

//********End of Function************

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

函数名称：KeyScan

函数功能：按键扫描

入口参数：无

返回参数：无

备    注：无

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

void KeyScan(void)

{

       if((P3&0xFF)
== 0xFB) //定点循环扫描该按键

       {

              P3
= 0xFF;

              Delay(50);             //延时去抖动

              if((P3&0xFF)
== 0xFB)

              {

                     if(c>=15)

                            c
= 0;

                     else

                            c++;

              }

       }

       else

       {

              P3
= 0xFF;

       }

}

void main(void)

{

       P3
= 0xFF; //初始化为输入形式

       while(1)

       {

              KeyScan();

              Bit
= 1;

              P0
= LED[15-c];   

              Bit
= 0;

              Seg
= 1;

              P0
= 0xEF;

              Seg
= 0;

              Delay(50);

       }

}

矩阵键盘

我的开发板上有由16个按键组成的4×4矩阵键盘：行接到P3.0~P3.3，列接到P3.4~P3.7。

下面的程序中，定义这16个按键依次为0~F，当对应的按键按下时，由数码管进行显示。

#include "KeyPad.h"

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

函数名称：Delay

函数功能：延时

入口参数：uint t—要延时的毫秒数

返回参数：无

备    注：无

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

void Delay(uint t)

{

       uint
i;

       while(t--)

       {

              for
(i=0;i<125;i++)

              {}

       }

}

//********End of Function************

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

函数名称：KeyScan

函数功能：键盘扫描

入口参数：无

返回参数：uchar—扫描到键值

备    注：无

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

uchar KeyScan(void)

{

       uchar
KeyValue;

       uchar
ScanCode;

       P3
= 0xF0;                   //全0行扫描码

       if((P3&0xF0)!=0xF0)    //若有键按下 

       {

              Delay(20);
           //延时去抖

              if((P3&0xF0)!=0xF0)    //确有键按下

              {

                     ScanCode
= 0xFE;

                     while(ScanCode
!= 0xEF)     //逐行扫描

                     {

                            P3
= ScanCode;            //发送扫描码

                            if((P3&0xF0)!=0xF0)    //本行有键按下           

                            {

                                   KeyValue
= P3;

                                   return
KeyValue;     //返回扫描码

                            }    

                            else

                            {

                                   ScanCode
= _crol_(ScanCode,1);

                                   //本行没有键按下，扫描码左移1位,继续扫描

                            }

                     }

              }

       }

       return
0; 

}

//********End of Function************

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

函数名称：GetCode

函数功能：根据扫描到的键值得到要显示的字型码

入口参数：uchar i—扫描到的键值

返回参数：uchar—要送数码管显示的字型码

备    注：无

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

uchar GetCode(uchar i)

{

       uchar
num;

       switch(i)

       {

              case
0xEE:      num = LED[0];      break;

              case
0xDE:     num = LED[1];      break;

              case
0xBE:      num = LED[2];      break;

              case
0x7E:      num = LED[3];      break;

              case
0xED:     num = LED[4];      break;

              case
0xDD:     num = LED[5];      break;

              case
0xBD:     num = LED[6];      break;

              case
0x7D:     num = LED[7];      break;

              case
0xEB:      num = LED[8];      break;

              case
0xDB:     num = LED[9];      break;

              case
0xBB:      num = LED[10];    break;

              case
0x7B:      num = LED[11];     break;

              case
0xE7:      num = LED[12];    break;

              case
0xD7:     num = LED[13];    break;

              case
0xB7:      num = LED[14];    break;

              case
0x77:      num = LED[15];    break;

              default:    break;           

       }

       return
num;   

}

//********End of Function************

void main(void)

{

       uchar
key,led;

       while(1)

       {

              key
= KeyScan();

              led
= GetCode(key);

              Bit
= 1;

              P0
= led;

              Bit
= 0;

              Seg
= 1;

              P0
= 0xEF;

              Seg
= 0;

              Delay(50);

       }

}