AT89S52键盘程序

/********************************************************************/

//键盘扫描子程序      获取键值函数

/****************************************************************************/

uchar keyscan(void)

{ uchar temp;

P0=0xfe;               //第一行置低

temp=P0;

temp&=0xf0;

if(temp!=0xf0)

    {

delay_nms(10);

if(temp!=0xf0)

{

   switch(temp)                     //根据列线获取第一行的键值

   {

     case 0xe0: key=3; break;

     case 0xd0: key=2; break;

     case 0xb0: key=1; break;

     case 0x70: key=0; break;

       }

}

}

P0=0xfd;                        //扫描第二行，置低

temp=P0;

temp&=0xf0;

if(temp!=0xf0)

{

delay_nms(10);

if(temp!=0xf0)

{

   switch(temp)

   {

     case 0xe0: key=7; break;

     case 0xd0: key=6; break;

     case 0xb0: key=5; break;

     case 0x70: key=4; break;

       }

    }

}

P0=0xfb;                        //扫描第三行，置低

temp=P0;

temp&=0xf0;

if(temp!=0xf0)

{

delay_nms(10);

if(temp!=0xf0)

{

   switch(temp)

   {

     case 0xe0: key=11; break;

     case 0xd0: key=10; break;

     case 0xb0: key=9; break;

     case 0x70: key=8; break;

       }

    }

}

P0=0xf7;                       //扫描第四行，置低

temp=P0;

temp&=0xf0;

if(temp!=0xf0)

{

delay_nms(10);

if(temp!=0xf0)

{

   switch(temp)

   {

     case 0xe0: key=15; break;

     case 0xd0: key=14; break;

     case 0xb0: key=13; break;

     case 0x70: key=12; break;

       }

      }

    }

else

  {

   ;

  }

   return(key);

}