4X4 matrix keyboard (lookup table method) C language programming

According to the key value code returned by scanning the keyboard, the key value is looked up in the key value code table to obtain the key value and send it to the digital tube for display.

When the power is turned on, the digital tube displays “-”.

When a key is pressed, the digital tube displays the key value of the pressed key and the buzzer sounds once. */

#include
#include

#define uchar unsigned char
#define uint  unsigned int

sbit BEEP = P3^6; //Buzzer drive line

uchar key;

unsigned char code disp_code[]={
              0xc0,0xf9,0xa4,0xb0,0x99,0x92,0x82,0xf8,
              0x80,0x90,0x88,0x83,0xc6,0xa1,0x86,0x8e,0xbf};

unsigned char code key_code[]={
              0xee,0xde,0xbe,0x7e,0xed,0xdd,0xbd,0x7d, 
              0xeb,0xdb,0xbb,0x7b,0xe7,0xd7,0xb7,0x77 };

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

  Delay subfunction

**********************************************************/
void delayms(uint ms) 
{
   uchar t;
   while(ms--)
   { 
     for(t = 0; t < 120; t++);
   }
}

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

  x*0.14MS delay sub-function

**********************************************************/
void delay0(uchar x)    
{
   uchar i;
   while(x--)
   {
     for (i = 0; i<13; i++) {;}
   }
}

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

  Buzzer driver subfunction

**********************************************************/
void beep()
{
  uchar i;
  for (i=0;i<180;i++)
  {
    delay0(5);
    BEEP=!BEEP; //BEEP inversion
  } 
   BEEP=1; //turn off the buzzer
   delayms(250); //delay     
}

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

Keyboard scanning subroutine

****************************************************** ********/
fly keyscan()
{
   fly scan1,scan2,keycode,j;

   P1=0xf0;
   scan1=P1;
   if((scan1&0xf0)!=0xf0) //Judge whether the key is pressed
   {
     delayms(30); //Delay 30ms
     scan1=P1;
     if((scan1&0xf0)!=0xf0) //Secondary judgment whether the key is pressed
     {
        P1=0x0f;
        scan2=P1;
        keycode=scan1|scan2; //Combined into key code

        for(j=0;j<=15;j++)
        {
           if(keycode== key_code[j]) //Look up the table to get the key value
           {
              key=j;
              return(key);
           }
        } 
     }
   }
   else P1=0xff;

   return (16);
}

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

  Determine whether the key is pressed sub function

**********************************************************/
void  keydown()
{  
   P1=0xf0;
   if((P1&0xf0)!=0xf0)
   {
     keyscan();
     P0=disp_code[key];
     beep();
   }
}

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

Main function

**************************************************************/
main()
{
   P0 = 0xbf;
   P2 = 0x7f; //The digital tube displays "-" 
    P1 = 0xff;

   while(1)
   {
     keydown();     
   }
}