4x4+

4x4矩阵键盘扫描,读入键值,没有按键操作返回0xff,有的话返回输入的键值

#define _4X4_C_
#include "reg51.h"
#include "4x4.h"
sbit LED=P1^3;
unsigned char kn;
void delay10ms(unsigned char time);
unsigned char readkeynumber_4x4(void);
void shan(unsigned char n);
void main()
{		
	shan(1);
	while(1)
	{
		kn=readkeynumber_4x4();
		if(kn!=0xff)
		{
			shan(kn);
		}
	}
	
}
unsigned char readkeynumber_4x4()
{
	
	unsigned char i,j;
	P0=0X0F;
	if((P0&0X0F)!=0X0F)///判断是否有按键
	{	
		
		for(i=0;i<4;i++)//逐行扫描
		{
			P0=~(0X01<<(i+4));
			if((P0&0X0F)!=0X0F)//判断某行是否有按键
			{
				for(j=0;j<4;j++)
				{
					if(((P0>>j)&0x01)==0)//判断按键具体的列
					return i*4+j;//根据按键所属的行列计算键值
				}
			}
		}
		while((P0&0X0F)!=0X0F);//等按键释放
	}

	return 0xff;//无按键返回0xff
}
void delay10ms(unsigned char time)
{
	unsigned char i;
	int j;
	for(i=time;i>0;i--)
	{
		for(j=800;j>0;j--);
	}
}
void shan(unsigned char n)
{
	unsigned char i;
	for(i=n;i>0;i--)
	{
		LED=0;
		delay10ms(40);
		LED=1;
		delay10ms(40);
	}
}