蓝桥杯之单片机学习（六）——矩阵键盘的扫描原理与基本应用

文章目录

• ​​一、训练任务​​
• ​​二、原理图​​
• ​​三、代码展示​​
• ​​注意事项​​

一、训练任务

在CT107D单片机综合训练平台上，首先将J5处的跳帽接到1-2引脚， 使按键S4-S19按键组成4X4的矩阵键盘。在扫描按键的过程中，发现有按键触发信号后(不做去抖动)，待按键松开后，在数码管的第一位显示相应的数字:从左至右，从上倒下，依次显示0~F.

二、原理图

从左端输入低电平为0时，即为扫描该行，如果按键按下，右端输出低电平为0，如果按键没按下，右端输出高电平为1。

对所有行进行输入，如1011，则是对第二行进行扫描，然后对列依次进行检测，检测到1，则是没有按下，检测到0则按键按下。

三、代码展示

#include <reg52.h>

typedef unsigned int uint;
typedef unsigned char uchar;

sfr P4 = 0XC0;

sbit R1 = P3^0;
sbit R2 = P3^1;
sbit R3 = P3^2;
sbit R4 = P3^3;

sbit C4 = P3^4;
sbit C3 = P3^5;
sbit C2 = P4^2; //P36 -> P42
sbit C1 = P4^4; //P37 -> P44

void DelayK(uint n)
{
  while(n--);
}

uchar code SMG_duanma[18] = 
  {0xc0,0xf9,0xa4,0xb0,0x99,0x92,0x82,0xf8,0x80,0x90,
   0x88,0x80,0xc6,0xc0,0x86,0x8e,
   0xbf,0x7f};//分别是0-9（对应下标），A-F，“-”，“.”

//配置HC138
void SelectHC138(uchar channel)
{
  switch(channel)
  {
    case 4:
      P2 = (P2 & 0X1F) | 0X80;
    break;
    case 5:
      P2 = (P2 & 0X1F) | 0Xa0;
    break;
    case 6:
      P2 = (P2 & 0X1F) | 0Xc0;
    break;
    case 7:
      P2 = (P2 & 0X1F) | 0Xe0;
    break;
  }
}

//初始化系统
void Initsys()
{
  SelectHC138(5);
  P0 = 0X00;//关闭蜂鸣器和继电器
  SelectHC138(4);
  P0 = 0XFF;//关闭LED
}

void DisplayKeyNum(uchar dat)
{
  SelectHC138(6);
  P0 = 0X01;
  SelectHC138(7);
  P0 = SMG_duanma[dat];
}

uchar key_num;
void ScanKeyMulti()
{
  R1 = 0;
  R2 = R3 = R4 = 1;
  C1 = C2 = C3 = C4 = 1;
  if(C1 == 0)
  {
    key_num = 0;
    DisplayKeyNum(key_num);
    while(C1 == 0);
  }
  else if(C2 == 0)
  {
    key_num = 1;
    DisplayKeyNum(key_num);
    while(C2 == 0);
  }
  else if(C3 == 0)
  {
    key_num = 2;
    DisplayKeyNum(key_num);
    while(C3 == 0);
  }
  else if(C4 == 0)
  {
    key_num = 3;
    DisplayKeyNum(key_num);
    while(C4 == 0);
  }
  R2 = 0;
  R1 = R3 = R4 = 1;
  C1 = C2 = C3 = C4 = 1;
  if(C1 == 0)
  {
    key_num = 4;
    DisplayKeyNum(key_num);
    while(C1 == 0);
  }
  else if(C2 == 0)
  {
    key_num = 5;
    DisplayKeyNum(key_num);
    while(C2 == 0);
  }
  else if(C3 == 0)
  {
    key_num = 6;
    DisplayKeyNum(key_num);
    while(C3 == 0);
  }
  else if(C4 == 0)
  {
    key_num = 7;
    DisplayKeyNum(key_num);
    while(C4 == 0);
  }
  R3 = 0;
  R2 = R1 = R4 = 1;
  C1 = C2 = C3 = C4 = 1;
  if(C1 == 0)
  {
    key_num = 8;
    DisplayKeyNum(key_num);
    while(C1 == 0);
  }
  else if(C2 == 0)
  {
    key_num = 9;
    DisplayKeyNum(key_num);
    while(C2 == 0);
  }
  else if(C3 == 0)
  {
    key_num = 10;
    DisplayKeyNum(key_num);
    while(C3 == 0);
  }
  else if(C4 == 0)
  {
    key_num = 11;
    DisplayKeyNum(key_num);
    while(C4 == 0);
  }

  R4 = 0;
  R2 = R3 = R1 = 1;
  C1 = C2 = C3 = C4 = 1;
  if(C1 == 0)
  {
    key_num = 12;
    DisplayKeyNum(key_num);
    while(C1 == 0);
  }
  else if(C2 == 0)
  {
    key_num = 13;
    DisplayKeyNum(key_num);
    while(C2 == 0);
  }
  else if(C3 == 0)
  {
    key_num = 14;
    DisplayKeyNum(key_num);
    while(C3 == 0);
  }
  else if(C4 == 0)
  {
    key_num = 15;
    DisplayKeyNum(key_num);
    while(C4 == 0);
  }
  
}

void main()
{
  Initsys();
  while(1)
  {
    ScanKeyMulti();
  }
}

注意事项

1. 眺帽接到KBD，才是矩阵键盘
2. 在头文件​​reg52.h​​​中没有定义P4的地址，需要自己配置，为​​sfr P4 = 0XC0​​
3. 看电路图是否引脚是否发生变化