4io_10key.c

4个IO接10个按键的扫描方法,按这个方法8个IO可以接成36个按键

/**************************************
									  
	4个IO接10个按键的方法			  
									  
***************************************/
#include <reg51.h>
#include <intrins.h>

#define uchar unsigned char
#define uint  unsigned int
#define ulong unsigned long

sbit KeyPort0 =P2^0; 
sbit KeyPort1 =P2^1;
sbit KeyPort2 =P2^2;
sbit KeyPort3 =P2^3;

sbit LED1=P1^0;
sbit LED2=P1^1;
sbit LED3=P1^2;
sbit LED4=P1^3;
sbit LED5=P1^4;
sbit LED6=P1^5;
sbit LED7=P1^6;
sbit LED8=P1^7;
//-------------------------------------------------------------------------------
unsigned char KeyScan()
{
	uchar _keyvalue;
	P2 |= 0xff;
	_keyvalue=0;
	
	if( !KeyPort0 )
		_keyvalue = 1;
	else if( !KeyPort1 )
		_keyvalue = 2;
	else if( !KeyPort2 )
		_keyvalue = 3;
	else if( !KeyPort3 )
		_keyvalue = 4;
	else
	{
		KeyPort0 =0;
		if( !KeyPort1 )
			_keyvalue = 5;
		else if( !KeyPort2 )
			_keyvalue = 6;
		else if( !KeyPort3 )
			_keyvalue = 7;
		else
		{
			KeyPort1 =0;
			if( !KeyPort2 )
				_keyvalue = 8;
			else if( !KeyPort3 )
				_keyvalue = 9;
			else
			{
				KeyPort2 =0;
				if( !KeyPort3 )
					_keyvalue = 10;
			}
		}
	} 
	return _keyvalue; 
}
//-------------------------------------------------------------------------------
void main ()
{
	while(1)
	{
		switch(KeyScan())
		{
			case   1:  P1=0x01;  break;//key1 00
			case   2:  P1=0x02;  break;//key2 01
			case   3:  P1=0x04;  break;//key3 02
			case   4:  P1=0x08;  break;//key4 03				
			case   5:  P1=0x10;  break;//key5 04
			case   6:  P1=0x20;  break;//key6 05
			case   7:  P1=0x40;  break;//key7 06
			case   8:  P1=0x80;  break;//key8 07					
			default:   break;    	
		}
	}
}