HOLTEK MCU-4X4 keyboard using software scanning

The 4X4 keyboard corresponds to 16 numbers from 0 to F. Pressing any key will display the corresponding number on the common anode seven-segment display.

Circuit Description:

        Circuit

        Port B of the HT46F49E is connected to a common anode seven segment display.

        Since a common anode seven-segment digital display is used, a resistor is connected in series to each pin of port B for voltage division. Because each segment of the seven-segment display can be regarded as a light-emitting diode, VCC is enough to burn out the segment, so a resistor should be connected in series to each segment to divide the voltage with the light-emitting diode to protect the seven-segment display.

        Port A of the HT46F49E is connected to a 4X4 keyboard. PA7-PA0 sends out a row scan code, one of the pins sends out 0, the rest send out 1, and PA7-PA4 send out 0 in turn. If a key is pressed, PA3-PA0 will receive the information of which key is pressed. Combining the row scan code of PA7-PA4 and the information of the key pressed by PA3-PA0 can determine which key is pressed.

      Complete program code download address: http://www.51hei.com/f/htjp.rar

program:

#include "HT46F49E.H"

const unsigned char number[]={

0x81,0xcf,0x92,0x86,

0xcc,0xa4,0xa0,0x8f,

0x80,0x84,0x88,0xe0,

0xb1,0xc2,0xb0,0xb8};

unsigned int key_code;

void scan_keypressed()

{

    unsigned int i,scan_code;

    scan_code=0xef;

    key_code=0;

    for(i=0;i<4;i++)

    {

        _pa=scan_code;

        if(_pa0==0)

            key_code=i*4+1;

        if(_pa1==0)

            key_code=i*4+2;

        if(_pa2==0)

            key_code=i*4+3;

        if(_pa3==0)

            key_code=i*4+4;

        _rl(&scan_code);

    }  

}

void scan_keyeleased()

{

    switch(key_code%4)

    {

        case 1:while(!_pa0);

            break;

        case 2:while(!_pa1);

            break;

        case 3:while(!_pa2);

            break;

        case 0:while(!_pa3);

            break;  

    }  

}

void main()

{

    unsigned int key_old,led;

    _pcc=0x00;

    _pbc=0x00;

    _pac=0x0f;

    led=0;

    _pb=number[0];

    while(1)

    {

        scan_keypressed();

        if(key_code>0)

        {

            key_old=key_code;

            _delay(20000);

            scan_keypressed();

            if(key_old==key_code)

            {

                scan_keyeleased();

                led=key_code-1;

                _pb=number[led];

            }

        }

    }

}