51 single chip microcomputer learning - 5-- independent buttons

principle

Button Introduction

A touch switch is an electronic switch. When in use, lightly press the switch button to turn on the switch. When you release your hand, the switch is turned off. The switch we use is shown in the figure below:

Independent button principle

When the key is closed and opened, the contact will jitter.

Hardware debounce circuit

Software debounce

We can use the delay function

Code

Use independent keyboards K1, K2, K3, and K4 to control the on and off of the four LED lights on the left.

#include

typedef unsigned char u8;

typedef unsigned int u16;

sbit K1=P3^1; //The first button

sbit K2=P3^0; //The second button

sbit K3=P3^2; //The third button

sbit K4=P3^3; //The fourth button

sbit led1=P2^0;

sbit led2=P2^1;

sbit led3=P2^2;

sbit led4=P2^3;

void delay(u16 i)

{

while(i--);

}

void main()

{

while(1)

{

if(K1==0)//Judge whether it is pressed

{

delay(100); //If you press the button to cancel the bounce

if(K1==0)//Judge whether it is pressed

{

led1=~led1;

while(!K1); //Check if the button is released

}

}

if(K2==0)//Judge whether it is pressed

{

delay(100); //If you press the button to cancel the bounce

if(K2==0)//Judge whether it is pressed

{

led2=~led2;

while(!K2);//Check if the button is released

}

}

if(K3==0)//Judge whether it is pressed

{

delay(100); //If you press the button to cancel the bounce

if(K3==0)//Judge whether it is pressed

{

led3=~led3;

while(!K3);//Check if the button is released

}

}

if(K4==0)//Judge whether it is pressed

{

delay(100); //If you press the button to cancel the bounce

if(K4==0)//Judge whether it is pressed

{

led4=~led4;

while(!K4); //Check if the button is released

}

}

}

}