key.h

用按键来产生不同的频率

#ifndef KEY_H
#define KEY_H
#include<reg52.h>
#define uchar unsigned char
#define uint unsigned int


uchar getch()
{
	uchar ROW=0,LINE=0,Z=0,k=255;
	P2=0xff;				  //避免在读取单片机的端口信息时发生数据错误，故先给读取端口上高电平
	P2=0x0f;
	if(P2!=0x0f)
	{
		if(P2!=0x0f)
		{
			ROW=P2;
			P2=0xf0;
			LINE=P2;
			Z=ROW|LINE;
			switch(Z)
			{
				case 0x77:k=0;break;
				case 0x7b:k=1;break;
				case 0x7d:k=2;break;
				case 0x7e:k=3;break;
				case 0xb7:k=4;break;
				case 0xbb:k=5;break;
				case 0xbd:k=6;break;
				case 0xbe:k=7;break;
				case 0xd7:k=8;break;
				case 0xdb:k=9;break;
				case 0xdd:k=10;break;
				case 0xde:k=11;break;
				case 0xe7:k=12;break;
				case 0xeb:k=13;break;
				case 0xed:k=14;break;
				case 0xee:k=15;break;
			}
			while(P2!=0xf0);		   //确保按键松开时才显示，否则按键未松开时已有显示
		}							
	}
	return k;
}
#endif