16个阵列键盘驱动程序.txt

《爱上单片机》配书光盘

#define KEY P1 //键盘所连接的I/O接口组定义

/*********************************************************************************************
函数名：16个阵列式键盘驱动程序
调  用：? = Key ();
参  数：无
返回值：unsigned char 键值0~16
结  果：有键按下时返回值为键值1~16，无键按下时返回值为0
备  注：在主函数中不断调用
/**********************************************************************************************/
unsigned char Key (void){ //4*4阵列键盘处理程序
unsigned char a,b,c;
KEY = 0x0f; //设定键盘初始电平状态
if (KEY != 0x0f){ //读取键盘状态是否改变
   Delay (20); //延时20ms去抖动
   if (KEY != 0x0f){ //重新读取
	  a = KEY; //寄存状态值到a
	}
	KEY = 0xf0; //设定键盘反向电平状态
	c = KEY; //读取反向电平状态值到c
	a = a|c; //a与c相或
	switch(a){ //键盘状态查表
	   case 0xee: b = 1; break;
	   case 0xed: b = 2; break;
	   case 0xeb: b = 3; break;
	   case 0xe7: b = 4; break;
	   case 0xde: b = 5; break;
	   case 0xdd: b = 6; break;
	   case 0xdb: b = 7; break;
	   case 0xd7: b = 8; break;
	   case 0xbe: b = 9; break;
	   case 0xbd: b = 10; break;
	   case 0xbb: b = 11; break;
	   case 0xb7: b = 12; break;
	   case 0x7e: b = 13; break;
	   case 0x7d: b = 14; break;
	   case 0x7b: b = 15; break;
	   case 0x77: b = 16; break;
	   default:   b = 0 ; break;
	   }
	}
return (b); //将b中的键值代号送入函数返回值
}
/**********************************************************************************************/