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问 用89c2051做了一个键盘，P1.0-P1.3接上拉电阻，程序如下：
uchar getkey()
{
    uchar recode,key;               
    uchar sccode;
    P1=0xF0;
    if((P1&0xF0)!=0xF0)                   
         {                 
            delay(200);                 //延时1MS
        if((P1&0xF0)!=0xF0)
        {
            sccode=0xFE;
        while((sccode&0x10)!=0)
        {                                 P1=sccode;
                 if((P1&0xF0)!=0xF0)
                                          {
                                     recode=(P1&0xF0)|0x0F;
         keydd=0；                         key=(~sccode)+(~recode);
         key=changekey(key);
         return (key);                        }
    else sccode=(sccode<<1)|0x01;
    }                
    }
    }
    if((P1&0xF0)==0xF0)
        {
        delay(200);
        if((P1&0xF0)==0xF0)
            {
             keydd=1;
             return 0;
             }
        }  
}

uchar changekey(uchar keystate)
{
    switch(keystate)
        {
               
            case 0x41: keystate=0x47;break;
            case 0x42: keystate=0x49;break;
            case 0x44: keystate=0x45;break;
            case 0x48: keystate=0x42;break;
            case 0x22: keystate=0x48;break;
            case 0x24: keystate=0x46;break;
            case 0x28: keystate=0x43;break;
            case 0x11: keystate=0x51;break;
            case 0x12: keystate=0x16;break;
            case 0x14: keystate=0x11;break;
            case 0x18: keystate=0x41;break;

            *case 0x01: keystate=0x50;break;
            *case 0x02: keystate=0x15;break;
            *case 0x04: keystate=0x12;break;
            *case 0x08: keystate=0x44;break;

            default: break;
           }
    DOG=!DOG;
    return (keystate);
}

其中打*的四句不对,始终得不到我想要的值（如：keystate＝0x50等），其他的都没有问题。一直没有找到原因！请大家帮帮忙看下，谢谢 答 1: 有原理图吗 答 2: 当然不会有0x01,0x02,0x04,0x08的数据出现为1的位为行列相交的点，键按下时行列必然都有至少1点为1，即高4位和低4位必然都有为1的位！

当然不会有0x01,0x02,0x04,0x08的数据出现:
            *case 0x01: keystate=0x50;break;
            *case 0x02: keystate=0x15;break;
            *case 0x04: keystate=0x12;break;
            *case 0x08: keystate=0x44;break;

应该是0x81,0x82,0x84,0x88才对
            case 0x81: keystate=0x50;break;
            case 0x82: keystate=0x15;break;
            case 0x84: keystate=0x12;break;
            case 0x88: keystate=0x44;break;



答 3: 搞定了，感谢xwj！确实没有注意到这个问题！谢谢指点 答 4: 同意，同意 答 5: 对,是这个样子!!!对,是这个样子!!!