keybood_keyong_1.c

基于C8051F020的4×4键盘

#include <C8051F020.H>
#include"delay.h"
unsigned char a[4]={0xef,0xdf,0xbf,0x7f};		//从P5_4到P5_7依次发送低电平，对列写键值
unsigned char keyvalue=0;	

unsigned char coding(unsigned char n)		    //译码
{
	switch(n)
	{
		case 0xfe: return 0;break;		        //输入为 11111110 即为行号0 
		case 0xfd: return 1;break;		        //输入为 11111101 即为行号1 
		case 0xfb: return 2;break;		        //输入为 11111011 即为行号2 
		case 0xf7: return 3;break;		        //输入为 11110111 即为行号3 
	}
}

unsigned char keyscan()
{
	    
	unsigned char b;		
	unsigned char c;   
	unsigned char i;

	for(i=0;i<4;i++)		                    //列扫描，从P5_4开始到P5_7；i=0对应P5_4即第0列.
	{
	  
		P5=a[i];			                    //写键值，低电平有效
		b=P5;				                    //读健值，低电平有效
		b=b|0xf0;			                    //取低四位(P5_0--P5_3)的低电平；屏蔽高四位(P5_4--P5_7)的低电平
		if(b!=0xff)
		{ 
	    	delay_nms(10);		                //去抖动
		 	c=P5;
		 	c=c|0xf0;
		 	if(b==c)
			keyvalue=i*4+coding(c);	            //键值=列号*4+行号
		 }
	  }
	 return keyvalue;
 }
 void main(void)
 {	 int i; 
  WDTCN     = 0xDE;
    WDTCN     = 0xAD;

	 P74OUT    = 0x0C;
    XBR2      = 0x40;
	     OSCXCN    = 0x60;
    for (i = 0; i < 3000; i++);  // Wait 1ms for initialization
    while ((OSCXCN & 0x80) == 0);
	while(1)
 keyscan();
 }