51 independent key basic experiment

Experimental principle ：

Method of detecting keys ：

Keyboard circuit diagram ：

 

（ One ） Row and column scanning （ The code is more complex ）

First enter a column as 0, Others are 1（ Determination of column coordinates ）, Take turns to detect whether there is output in each row 0（ Determination of row coordinates ）

Then enter the next column in turn as 0, The rest are listed as 1, All keys can be detected after all columns are completed .

( Two ） Line reversal method

Place column line （ Output line ） All for 0, At this time, the line （ Input line ） If any output is 0 Then a key in this line is pressed .

Setting line （ Output line ） All for 0, At this time, the line （ Input line ） If any output is 0 Then a key in this column is pressed .

Experimental code ：

#include "reg52.h"
typedef unsigned char u8;
typedef unsigned  int u16;

void delay_10us(u16 ten_us);  // The time delay function 
u8 key_matrix_ranks_scan(void);
u8 key_matrix_filp_scan(void);

#define KEY_MATRIX_PORT		P1
#define SMG_PORT	P0

u8 gsmg_code[17]={0x3f,0x06,0x5b,0x4f,0x66,0x6d,0x7d,0x07,
				0x7f,0x6f,0x77,0x7c,0x39,0x5e,0x79,0x71};	
 
void main()	   // Press the key S1-S16  Corresponding LED Wait for it to light up 0-F
{
	  u8 key=0;
	  while(1)
	  {
	  		key=key_matrix_filp_scan();
			if(key!=0)
				SMG_PORT=~gsmg_code[key-1];	   // The above array is a common Yin code , Take the inverse to get the common Yang code 
	  }
}


void delay_10us(u16 ten_us)	 
{
	 while(ten_us--);
}

u8 key_matrix_filp_scan(void)	 // Line reversal scanning 
{
	  u8 key_value=0;
	 
	 KEY_MATRIX_PORT=0x0f;			  // Column scan 
	 if(KEY_MATRIX_PORT!=0x0f)
	 {
	 	delay_10us(1000);		 // Desquamation 
		if(KEY_MATRIX_PORT!=0x0f)
		{
			switch(KEY_MATRIX_PORT)
			{
				case 0x07:key_value=1;break;
				case 0x0b:key_value=2;break;
				case 0x0d:key_value=3;break;
				case 0x0e:key_value=4;break;
			}
		
		KEY_MATRIX_PORT=0xf0;		  // Line scan 
		switch(KEY_MATRIX_PORT)
			{
				case 0x70:key_value=key_value;break;
				case 0xb0:key_value=key_value+4;break;
				case 0xd0:key_value=key_value+8;break;
				case 0xe0:key_value=key_value+12;break;
			}
		while(KEY_MATRIX_PORT!=0xf0);

		}
	  
	 }else
	 	key_value=0;   		  // There is no key press   return 0
	 return key_value;		   // Return to key number 

}



 u8 key_matrix_ranks_scan(void)	  // Determinant scan 
{
	   u8 key_value=0;
	   
	   KEY_MATRIX_PORT=0xf7;		// Low level of the first column 
	   if(KEY_MATRIX_PORT!=0xf7)
	   {
	   		delay_10us(1000);
			switch(KEY_MATRIX_PORT)
			{
				case 0x77:key_value=1;break;
				case 0xb7:key_value=5;break;	
				case 0xd7:key_value=9;break;
				case 0xe7:key_value=13;break;
			}			
	   }
	   while(KEY_MATRIX_PORT!=0xf7); // Wait for the key to release 

	   KEY_MATRIX_PORT=0xfb;		  
	   if(KEY_MATRIX_PORT!=0xfb)
	   {
	   		delay_10us(1000);
			switch(KEY_MATRIX_PORT)
			{
				case 0x7b:key_value=2;break;
				case 0xbb:key_value=6;break;
				case 0xdb:key_value=10;break;
				case 0xeb:key_value=14;break;
			}	
	   }
	   	while(KEY_MATRIX_PORT!=0xfb);  

	   KEY_MATRIX_PORT=0xfd;
	   if(KEY_MATRIX_PORT!=0xfd)
	   {
	   		delay_10us(1000);
			switch(KEY_MATRIX_PORT)
			{
				case 0x7d:key_value=3;break;
				case 0xbd:key_value=7;break;
				case 0xdd:key_value=11;break;
				case 0xed:key_value=15;break;
			}
	   }
   		while(KEY_MATRIX_PORT!=0xfd);

	   KEY_MATRIX_PORT=0xfe;
	   if(KEY_MATRIX_PORT!=0xfe)
	   {
	   		delay_10us(1000);
			switch(KEY_MATRIX_PORT)
			{
				case 0x7e:key_value=4;break;	
				case 0xbe:key_value=8;break;   
				case 0xde:key_value=12;break; 
				case 0xee:key_value=16;break;  
			}			
	   }
	   while(KEY_MATRIX_PORT!=0xfe);
	   return key_value;
}

experimental result ：

In line with expectations , When the keyboard is pressed S1-S16 The corresponding nixie tube is on 0-F character .