Function for scaning the 4*4 keypad

[mf1364]

Hi every body
I want a Function for scanning the 4*4 key pad , i am using MicroC compiler . I know that there is function in microC library
but , I want to write my own please help me

 

[ckshivaram]

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Code C - [expand]
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#include <18F452.h> 
#fuses EC_IO,NOWDT,NOPROTECT,BROWNOUT,PUT,NOLVP 
#use delay(clock=4000000)  
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7, ERRORS) 
 
//============================= 
 
//Keypad connection: 
#define row0 PIN_B4 
#define row1 PIN_B5 
#define row2 PIN_B6 
#define row3 PIN_B7 
#define col0 PIN_B0 
#define col1 PIN_B1 
#define col2 PIN_B2 
#define col3 PIN_B3 
 
// Keypad layout: 
char const KEYS[4][4] = 
{{'1','2','3','A'}, 
 {'4','5','6','B'}, 
 {'7','8','9','C'}, 
 {'*','0','#','D'}}; 
 
 
#define KBD_DEBOUNCE_FACTOR 33 // Set this number to apx n/333 where 
// n is the number of times you expect 
// to call kbd_getc each second 
 
void kbd_init() 
{ 
//set_tris_b(0xF0); 
//output_b(0xF0); 
port_b_pullups(true);  
} 
 
short int ALL_ROWS (void) 
{ 
if(input (row0) & input (row1) & input (row2) & input (row3)) 
   return (0); 
else 
   return (1); 
} 
 
 
 
char kbd_getc() 
{ 
static byte kbd_call_count; 
static short int kbd_down; 
static char last_key; 
static byte col; 
 
byte kchar; 
byte row; 
 
kchar='\0'; 
 
if(++kbd_call_count>KBD_DEBOUNCE_FACTOR) 
  { 
   switch (col) 
     { 
      case 0: 
        output_low(col0); 
        output_high(col1); 
        output_high(col2); 
        output_high(col3); 
        break; 
    
      case 1: 
        output_high(col0); 
        output_low(col1); 
        output_high(col2); 
        output_high(col3); 
        break; 
 
      case 2: 
        output_high(col0); 
        output_high(col1); 
        output_low(col2); 
        output_high(col3); 
        break; 
 
      case 3: 
        output_high(col0); 
        output_high(col1); 
        output_high(col2); 
        output_low(col3); 
        break; 
      } 
 
   if(kbd_down) 
     { 
      if(!ALL_ROWS()) 
        { 
         kbd_down=false; 
         kchar=last_key; 
         last_key='\0'; 
        } 
     } 
   else 
     { 
      if(ALL_ROWS()) 
        { 
         if(!input (row0)) 
            row=0; 
         else if(!input (row1)) 
            row=1; 
         else if(!input (row2)) 
            row=2; 
         else if(!input (row3)) 
            row=3; 
 
         last_key =KEYS[row][col]; 
         kbd_down = true; 
        } 
      else 
        { 
         ++col; 
         if(col==4) 
            col=0; 
        } 
     } 
   kbd_call_count=0; 
  } 
return(kchar); 
} 
 
//=========================== 
void main() 
{ 
char k; 
 
kbd_init(); 
 
printf("\r\Starting ..."); 
 
while(TRUE) 
  { 
   k=kbd_getc(); 
   if(k!=0) 
     { 
      if(k=='*') 
         printf("%c", '*'); 
      else 
         printf("%c", k); 
     } 
  } 
 
}

---

 

[mf1364]

Thank you very much Mr ckshivaram , but I am so amateur in c language so can you explain line by line and can you change this code for microC compiler because I am using the Micro C compiler, and I want to show output on a character Lcd so i dont need RS232 protocol by the way so thanks for your reply