51矩阵键盘

//按键码表
uchar code KeyCodeTable[]=
{
      0x11,0x12,0x14,0x18,0x21,0x22,0x24,0x28,0x41,0x42,0x44,0x48,0x81,0x82,0x84,0x88
};
//延迟小程序，一般20ms
void Delay(void)
{
     uchar i;
    for(i=0;i<200;i++);
}
//按键检测程序
uchar Keys_Scan(void)
{
     uchar sCode,kCode,i,k;
    P1 = 0xf0;
    //是否有键被按下
    if((P1&0xf0)!=0xf0)
    {
         Delay();
        if((P1&0xf0)!=0xf0)
        {
             sCode = 0xfe;
            for(k=0;k<4;k++)
            {
                 P1 = sCode;
                if((P1&0xf0)!=0xf0)
                {
                     kCode = ~P1;
                    for(i=0;i<16;i++)
                    {
                         if(kCode == KeyCodeTable[i])
                            return i;
                    }
                }
                else 
                {
                    sCode = _crol_(sCode,1);
                }
            }
        }
    }
    return -1;
}