键盘的应用和分类：
键盘分为编码键盘和非编码键盘，键盘上闭合键的识别是由专门的硬件编码器实现，并产生键编码号或者是键值的成为编码键盘，如计算机的键盘
靠软件编程来识别的称为非编码键盘；
在单片机组成的各种系统中，用的最多的是非编码键盘，也有用到编码键盘的
非编码键盘又有独立键盘和矩阵键盘。
要先像键盘里面先写1；在读取操作
示例代码：
#include<reg52.h>
#define uint unsigned int
#define uchar unsigned char
sbit ld1 = P1^0;
sbit key1 = P3^4;
sbit dula = P2^6;
sbit wela = P2^7;
uchar num;
uchar code table[]={0x3f,0x06,0x5b,0x4f,
0x66,0x6d,0x7d,0x07,
0x7f,0x6f,0x77,0x7c,
0x39,0x5e,0x79,0x71};
void display(num);
main()
{
P3 = 0xff;
while(1)
{
display(num);
if(key1==0)
{
ld1 = 0;
num++;
if(num==10)
num = 0;
while(key1!=1);//松手检测
}
else
ld1 = 1;
}
}
void display(num)
{
wela = 1;
P0 = 0xfe;
wela = 0;
P0 = 0x0;
dula = 1;
P0 = table[num];
dula = 0;
dula = 1;//关灯操作
P0 = 0x0;
dula = 0;
}
View Code
这个程序看上去无懈可击，但是在实际过程中，有一个相当大打bug，那就是，你按住键盘的时候，数码管不显示数字，这不是很坑爹，所以，位选信号是开始就要打开的正确的代码是
#include<reg52.h>
#define uint unsigned int
#define uchar unsigned char
sbit ld1 = P1^0;
sbit key1 = P3^4;
sbit dula = P2^6;
sbit wela = P2^7;
uchar num;
uchar code table[]={0x3f,0x06,0x5b,0x4f,
0x66,0x6d,0x7d,0x07,
0x7f,0x6f,0x77,0x7c,
0x39,0x5e,0x79,0x71};
void display(num);
main()
{
P3 = 0xff;
wela = 1;
P0 = 0xfe;//打开位选线
wela = 0;
while(1)
{
if(key1==0)
{
ld1 = 0;
num++;
if(num==10)
num = 0;
while(key1!=1);//松手检测
}
else
ld1 = 1;
dula = 1;
P0 = table[num];//在循环中不断送入段选
dula = 0;
}
}
去抖：由于按键接触的时候会出现抖动，所以，要进行去抖操作
去抖有硬件消抖和软件消抖
硬件消抖要用专门的硬件消抖电路，导致外部电路复杂，在单片机中用不着
软件消抖，一般是延时5毫秒检测
#include<reg52.h>
#define uint unsigned int
#define uchar unsigned char
sbit ld1 = P1^0;
sbit key1 = P3^4;
sbit dula = P2^6;
sbit wela = P2^7;
uchar num;
uchar code table[]={0x3f,0x06,0x5b,0x4f,
0x66,0x6d,0x7d,0x07,
0x7f,0x6f,0x77,0x7c,
0x39,0x5e,0x79,0x71};
void delay(uint x);
main()
{
P3 = 0xff;
wela = 1;
P0 = 0xfe;//打开位选线
wela = 0;
while(1)
{
if(key1==0)
{
delay(10);//延时十毫秒
if(key1 == 0)//确实按下去了
{
ld1 = 0;
num++;
if(num==10)
num = 0;
while(key1!=1);//松手检测
delay(10); //检测是否松手
while(!key1);
}
}
else
ld1 = 1;
dula = 1;
P0 = table[num];//在循环中不断送入段选
dula = 0;
}
}
void delay(uint x)
{
uint y,z;
for(y=x;y>0;y--)
for(z=110;z>0;z--);
}
矩阵键盘：无论是矩阵键盘还是独立键盘，单片机检测其是否被按下去的依据都是一样的，也就是检测该键盘对应的I/O口是否为低电平，独立键盘有一段固定是低电平，单片机写程序时检测比较方便，电路时矩阵键盘的两端都与单片机deI/O口相连，因此在检测时，先送入一列为低电平，其余的全部为高电平，此时我们确定了列数，然后立即轮流检测一次各行是否有低电平，检测到某一行为低电平（这是我们有确定了行数），着我们便可确定是哪一行哪一列的按键被按下去。
示例代码：
#include<reg52.h>
sbit wela =P2^6;
sbit dula = P2^7;
#define uchar unsigned char
#define uint unsigned int
void delay(uint z);
uchar num,num1,temp;
uchar keyscan();
uchar code table[]={0x3f,0x06,0x5b,0x4f,
0x66,0x6d,0x7d,0x07,
0x7f,0x6f,0x77,0x7c,
0x39,0x5e,0x79,0x71,0x0};
main()
{
wela = 1;
P0 = 0x0;
wela = 0;
while(1)
{
num1 = keyscan();
dula =1;
P0 = table[num1];
dula = 0;
}
}
void delay(uint z)
{
uint x,y;
for(x=z;x>0;x--)
for(y=110;y>0;y--);
}
uchar keyscan()
{
P3 = 0xfe;//1111 1110
temp = P3;
temp = temp&0xf0;//11110000
while(temp!=0xf0)//如果有键摁下
{
delay(5);//再次检测P3口
temp = P3;
temp = temp&0xf0;
while(temp!=0xf0)
{
temp = P3;
switch(temp)
{
case 0x7e:num = 1;
break;
case 0xbe:num = 2;
break;
case 0xde:num = 3;
break;
case 0xee:num = 4;
break;
}
while(temp!=0xf0)//松手检测
{
temp = P3;
temp = temp&0xf0;
}
}
}
P3 = 0xfd;//1111 1101
temp = P3;
temp = temp&0xf0;//11110000
while(temp!=0xf0)//如果有键摁下
{
delay(5);//再次检测P3口
temp = P3;
temp = temp&0xf0;
while(temp!=0xf0)
{
temp = P3;
switch(temp)
{
case 0x7d:num = 5;
break;
case 0xbd:num = 6;
break;
case 0xdd:num = 7;
break;
case 0xed:num = 8;
break;
}
while(temp!=0xf0)//松手检测
{
temp = P3;
temp = temp&0xf0;
}
}
}
P3 = 0xfb;//1111 1011
temp = P3;
temp = temp&0xf0;//11110000
while(temp!=0xf0)//如果有键摁下
{
delay(5);//再次检测P3口
temp = P3;
temp = temp&0xf0;
while(temp!=0xf0)
{
temp = P3;
switch(temp)
{
case 0x7b:num = 9;
break;
case 0xbb:num = 10;
break;
case 0xdb:num = 11;
break;
case 0xeb:num = 12;
break;
}
while(temp!=0xf0)//松手检测
{
temp = P3;
temp = temp&0xf0;
}
}
}
P3 = 0xf7;//1111 0111
temp = P3;
temp = temp&0xf0;//11110000
while(temp!=0xf0)//如果有键摁下
{
delay(5);//再次检测P3口
temp = P3;
temp = temp&0xf0;
while(temp!=0xf0)
{
temp = P3;
switch(temp)
{
case 0x77:num = 13;
break;
case 0xb7:num = 14;
break;
case 0xd7:num = 15;
break;
case 0xe7:num = 16;
break;
}
while(temp!=0xf0)//松手检测
{
temp = P3;
temp = temp&0xf0;
}
}
}
return num;
}
按键操作的数字有规律，第一行为0xfe,那么其次的数是7bde,加上e,0x7e,0xbe,0xde,0xee
第二行是0xfd，那么其次的数是7bde，加上d,0x7d,0xbd,0xdd,0xed
第三行是0xfb，那么其次的数是7bde，加上b,0x7b,0xbb,0xdb,0xeb,
第四行是0xf7，那么其次的数是7bde，加上7,0x77,0xb7,0xd7,,0xe7
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来源：https://www.cnblogs.com/fengdashen/p/3327186.html