AVR's simple and easy-to-use 4x4 matrix keyboard

// Crystal: 8.0000Mhz

//key.h

#ifndef _4X4_H_
#define _4X4_H_

#define No_key  255

#define key_port      PORTB 
#define key_port_ddr  DDRB 
#define key_port_pin  PINB

unsigned char keyboard_Scan(void);

#endif

//key.c

#include  
#include

#include "key.h"

const unsigned char key_table[16] =  
      { 
         1, 2, 3,12, 
         4, 5, 6,13, 
         7, 8, 9,14,                
         10,0,11,15, 
     };

void delay_1ms(void)                 //1ms延时函数
  {
    unsigned int i;
    for (i=0;i<1140;i++);
  }
  
void delay_nms(unsigned int n)       //N ms延时函数
  {
    unsigned int i=0;
    for (i=0;i    delay_1ms();
  }

//4x4 matrix keyboard scanning function

unsigned char keyboard_Scan(void) 
{ 
    unsigned char temp,key,row,Column;                         

    key_port_ddr = 0b00001111; // high four bits input row line / low four bits output column line 
    key_port = 0b11110000; // high four bits open pull-up resistor / low four bits output low level 
    delay_nus(5); // delay 5us 
    if((key_port_pin & 0xF0)!= 0xF0) // make an initial check to see if any key is pressed, if not, return 
   { // if not all row lines are 1, a key may be pressed 
     delay_nms(5); // delay debounce 

      //Set the initial value of the column line 3~0=1110        
     for(Column=0,key_port=0b11111110;Column<4;Column++) 
     {                 
         for(row=0,temp=0b11101111;row<4;row++)//Set the initial value of the row line 7~4=1110 
       {   
           while((key_port_pin & 0xF0)==(temp & 0xF0))//Enter the row line and check whether there is a key pressed in this row 
           { 
           key=4*row+Column;//Key code = 4*row input value + column scan valuekey 
           =key_table[key];//Keyboard code conversion key valuereturn 
            (key); 
            } 
          temp<<=1;//Shift the row line left by 1 bit 
        } 
      key_port=((key_port<<1)|0x01);//Shift the column line scan value left by 1 bit and scan the next row 
     } 
   } 
   return (No_key); 
}

//main.c

#include  
#include

#include "key.h"

void main(void)
{
  unsigned char Key;
  while(1)
   {
     Key = keyboard_Scan();            // 键盘扫描 
     switch(Key)
      {
        case 0:
        break;

        ......
  
       default:
       break;
     }
   }
}

I personally think it is better to use a timer for the delay in the main function.

The key_table array can be modified if the circuit connection is different