51 single chip matrix keyboard

uchar code KEY_TABLE[] =

{

    0x77,0xB7,0xD7,0xE7

0x7B,0xBB,0xDB,0xEB

0x7D,0xBD,0xDD,0xED

0x7E,0xBE,0xDE,0xEE

}; //The upper four bits are the columns, the lower four bits are the rows

uchar code TABLE[] =

{

    '1', '2', '3',

'4', '5', '6',

'7', '8', '9',

    'C', '0', 'A',

};

char key_scan()

{

uchar temp, key, i;

P1 = 0xf0; //1111 0000 

    //First scan the column and determine the column

    //Set the high four bits of the column pins to high level, and the low four bits of the row pins to low level. When the button is pressed, it will be pulled low.

    if (P1 != 0xf0)  

        {

            delay_ms(10);

            if (P1!= 0xf0)

            {

                temp = P1; //temp exists after pressing

                P1 = 0x0f;

                // Scan the line later to determine which line

                //Set the row pin, the lower four bits, to high level, and the column pin, the upper four bits, to low level. When the button is pressed, it will be pulled low.

                key = temp | P1;

                //Or the rows and columns, the position where the upper four bits are 0 is the column, and the position where the lower four bits are 0 is the row

                for (i = 0; i < 12; ++i) //Find the corresponding key and assign the corresponding character

                    if (key == KEY_TABLE[i])

                        break;

                return TABLE[i];

            }

        }

else

return 0x00;

}