Identification of 89C52 Matrix Keyboard

The matrix keyboards I have seen generally have two identification methods: scanning method and line inversion method. Taking a 4X4 matrix keyboard as an example, the scanning method is to set each row to 0 in turn, and then read the status of the column, so that the key status of the entire matrix keyboard can be identified through four scans. The amount of code required for this method is relatively long; while the line inversion method is relatively concise. It sets all 4 rows to 0 (0xf0) first, then reads the status of the column, then sets all the columns to 0 (0x0f), reads the status of the row, and determines the status of the entire row and column through (row|column). The scanning method takes up more program storage space (Program Space) than the line inversion method, but takes up less data storage space (Data Space).

The procedure is as follows

Scanning method:

#include
#define uchar unsigned char
#define uint unsigned int
uchar num,c;
uchar code SSEG[]={0x3f,0x06,0x5b,0x4f,0x66,0x6d,0x7d,0x07,0x7f,0x6f,0x77,0x7c,0x39,0x5e,0x79,0x71};

void delay1ms(uint z)
{
 uint x;
 uchar y;
 for(x=z;x>0;x--)
  for(y=110;y>0;y--);
}

void keyscan()
{
 uchar temp;
 P2=0xfe;
 temp=P2&0xf0;
 if(temp!=0xf0)
 {
  delay1ms(10);
  temp=P2&0xf0;
  if(temp!=0xf0)
  {
   temp=P2;
   switch(temp)
   {
    case 0xee:num=0;break;
    case 0xde:num=1;break;
    case 0xbe:num=2;break;
    case 0x7e:num=3;break;
   }
   while(temp!=0xf0)//松手检测
   {
    temp=P2;
    temp=temp&0xf0;
   }
  } 
 }
 P2=0xfd;
 temp=P2&0xf0;
 if(temp!=0xf0)
 {
  delay1ms(10);
  temp=P2&0xf0;
  if(temp!=0xf0)
  {
   temp=P2;
   switch(temp)
   {
    case 0xed:num=4;break;
    case 0xdd:num=5;break;
    case 0xbd:num=6;break;
    case 0x7d:num=7;break;
   }
   while(temp!=0xf0)
   {
    temp=P2;
    temp=temp&0xf0;
   }
  } 
 }
 P2=0xfb;
 temp=P2&0xf0;
 if(temp!=0xf0)
 {
  delay1ms(10);
  temp=P2&0xf0;
  if(temp!=0xf0)
  {
   temp=P2;
   switch(temp)
   {
    case 0xeb:num=8;break;
    case 0xdb:num=9;break;
    case 0xbb:num=10;break;
    case 0x7b:num=11;break;
   }
   while(temp!=0xf0)
   {
    temp=P2;
    temp=temp&0xf0;
   }
  } 
 }
 P2=0xf7;
 temp=P2&0xf0;
 if(temp!=0xf0)
 {
  delay1ms(10);
  temp=P2&0xf0;
  if(temp!=0xf0)
  {
   temp=P2;
   switch(temp)
   {
    case 0xe7:num=12;break;
    case 0xd7:num=13;break;
    case 0xb7:num=14;break;
    case 0x77:num=15;break;
   }
   while(temp!=0xf0)
   {
    temp=P2;
    temp=temp&0xf0;
   }
  } 
 }
}

void main()
{
 num=0xff;
 while(1)
 {
  keyscan();
  P1=~SSEG[num];
 }

}

Line reversal method:

#include
#define uchar unsigned char
#define uint unsigned int
uchar num;
uchar code SSEG[]={0x3f,0x06,0x5b,0x4f,0x66,0x6d,0x7d,0x07,0x7f,0x6f,0x77,0x7c,0x39,0x5e,0x79,0x71};

void delay1ms(uint z)
{
 uint x;
 uchar y;
 for(x=z;x>0;x--)
  for(y=110;y>0;y--);
}

void keyscan()
{
 uchar temp,z;
 P2=0xf0;
 if(P2!=0xf0)
 {
  delay1ms(10);
  if(P2!=0xf0)
  {
   temp=P2;
   P2=0x0f;
   z=temp|P2;
   temp=P2&0x0f;
   while(temp!=0x0f)//松手检测
   {
    temp=P2&0x0f; 
   }
   switch(z)
   {
    case 0xee: num =0; break;
          case 0xde: num =1; break;
          case 0xbe: num =2; break;
          case 0x7e: num =3; break;
          case 0xed: num =4; break;
          case 0xdd: num =5; break;
          case 0xbd: num =6; break;
          case 0x7d: num =7; break;
          case 0xeb: num =8; break;
          case 0xdb: num =9; break;    
          case 0xbb: num =10;break;
          case 0x7b: num =11;break;
          case 0xe7: num =12;break;
          case 0xd7: num =13;break;
          case 0xb7: num =14;break;
          case 0x77: num =15;break;
   }
  }
 }
}

void main()
{
 num=0xff;
 P2=0xff;
 while(1)
 {
  keyscan();
  P1=~SSEG[num];
 }
}