4x4 Keypad Interfacing Program with PIC16F877A

#include <pic.h>
/*   PIC Configuration Bit:
**   INTIO     - Using Internal RC No Clock
**   WDTDIS    - Wacthdog Timer Disable
**   PWRTEN    - Power Up Timer Enable
**   MCLREN    - Master Clear Enable
**   UNPROTECT - Code Un-Protect
**   UNPROTECT - Data EEPROM Read Un-Protect
**   BORDIS    - Borwn Out Detect Disable
**   IESODIS   - Internal External Switch Over Mode Disable
**   FCMDIS    - Monitor Clock Fail Safe Disable
*/
__CONFIG( WDTDIS & PWRTEN & UNPROTECT \
  & UNPROTECT & BORDIS);
 
#define FOSC 4000000
#define _delay_us(x) { unsigned char us; \
         us = (x)/(12000000/FOSC)|1; \
         while(--us != 0) continue; }
 
void _delay_ms(unsigned int ms)
{
  unsigned char i;
  do {
    i = 4;
    do {
      _delay_us(164);
    } while(--i);
  } while(--ms);
}
 
//****** LCD Functions declaration ******** //
void LCD_init(void);
void LCD_WriteCommand (unsigned char Command);
void LCD_WriteData (unsigned char Data);
 
void LCD_DisplayString (char row, char column, char *string);
void LCD_Cursor(char row, char column);
 
#define ENABLE_LCD              PORTD |= 0x80
#define DISABLE_LCD            PORTD &= ~0x80
#define SET_LCD_DATA           PORTD |= 0x20
#define SET_LCD_CMD            PORTD &= ~0x20
#define KB_PORT_OUT    PORTC
#define KB_PORT_IN    PORTC
 
//************************
 
void port_init(void)
{
 TRISB  = 0x00;  
 PORTB = 0x00;  
 TRISC  = 0xf0;//Key-board port, higer nibble - input, lower nibble - output
 PORTC = 0xff; 
 TRISD  = 0x0f;
 PORTD = 0x00;
}
 
 
//call this routine to initialize all peripherals
void init_devices(void)
{
 port_init();
 LCD_init(); 
} 
 
//****************** MAIN FUNCTION *******************
 
 int main(void)
{
   unsigned char upperNibble, keyCode, keyPressed, i;
   init_devices();
 
   LCD_DisplayString (1,1,"   WELCOME    ");
   LCD_WriteCommand(0xc0); //moving LCD cursor to second row
 
   while(1)
   {
        upperNibble = 0xff;
 
  for(i=0; i<4; i++)
     {
   _delay_ms(1);
   KB_PORT_OUT = ~(0x01 << i);
   _delay_ms(1); //delay for port o/p settling
   upperNibble = KB_PORT_IN | 0x0f;
 
   if (upperNibble != 0xff)
   {
     _delay_ms(20); //key debouncing delay
        upperNibble = KB_PORT_IN | 0x0f;
     if(upperNibble == 0xff) goto OUT;
 
     keyCode = (upperNibble & 0xf0) | (0x0f & ~(0x01 << i));
 
     while (upperNibble != 0xff)
       upperNibble = KB_PORT_IN | 0x0f;
 
     _delay_ms(20); //key debouncing delay
 
     switch (keyCode) //generating key characetr to display on LCD
     {
      case (0xee): keyPressed = '0'; 
        break;
   case (0xed): keyPressed = '1';
        break;
   case (0xeb): keyPressed = '2'; 
          break;
   case (0xe7): keyPressed = '3'; 
        break;
   case (0xde): keyPressed = '4'; 
        break;
   case (0xdd): keyPressed = '5'; 
        break;
   case (0xdb): keyPressed = '6'; 
        break;
   case (0xd7): keyPressed = '7'; 
        break;
   case (0xbe): keyPressed = '8'; 
        break;
   case (0xbd): keyPressed = '9'; 
        break;
   case (0xbb): keyPressed = 'A'; 
        break;
   case (0xb7): keyPressed = 'B'; 
        break;
   case (0x7e): keyPressed = 'C'; 
        break;
   case (0x7d): keyPressed = 'D'; 
        break;
   case (0x7b): keyPressed = 'E'; 
        break;
   case (0x77): keyPressed = 'F'; 
        break;
   default : keyPressed = 'X';
   }//end of switch
 
   LCD_WriteData(keyPressed); 
 
     OUT:;
    }//end of if
  }//end of for
 }//end of while(1)  
 
 return 0;    
}//end of main()
 
 
//***********************************************************************
//***********************   LCD Functions   ***************************** 
//***********************************************************************
 
// ********************************* 
// *** Initialize the LCD driver *** 
// ********************************* 
void LCD_init(void)
{
 _delay_ms(100); // wait for 100ms
 
 //SET_LCD_WRITE ;      // Set LCD in write mode
 
 LCD_WriteCommand (0x38); // 8 data lines
 LCD_WriteCommand (0x08); // display off
 LCD_WriteCommand (0x01); // clear LCD memory
 _delay_ms (10); // 10ms delay after clearing LCD
 LCD_WriteCommand (0x06); // cursor setting
 LCD_WriteCommand (0x0f); // display ON
}
 
 
// ********************************************** 
// *** Write a command instruction to the LCD *** 
// ********************************************** 
void LCD_WriteCommand (unsigned char Command)
{
 
 SET_LCD_CMD; // Set LCD in command mode
 
 PORTB = Command; // Load data to port
 
 ENABLE_LCD; // Write data to LCD
 
 asm("nop");     
 asm("nop");
 
 DISABLE_LCD; // Disable LCD 
 
 _delay_ms(1); // wait for 1ms
}
 
 
// ***************************************** 
// *** Write one byte of data to the LCD *** 
// ***************************************** 
void LCD_WriteData (unsigned char Data)
{
 SET_LCD_DATA; // Set LCD in data mode
 
 PORTB = Data; // Load data to port
 
 ENABLE_LCD; // Write data to LCD
 
 asm("nop");
 asm("nop");
 
 DISABLE_LCD; // Disable LCD
 
 _delay_ms(1); // wait for 1ms
}
 
 
// ********************************************************************* 
// *** Display a string at the specified row and column, from FLASH **** 
// ********************************************************************* 
void LCD_DisplayString (char row, char column, char *string)
{
 LCD_Cursor (row, column);
 while (*string)
  LCD_WriteData(*string++);
}
 
 
// *************************************************** 
// *** Position the LCD cursor at "row", "column". *** 
// *************************************************** 
void LCD_Cursor (char row, char column)
{
 switch (row) 
 {
  case 1: LCD_WriteCommand (0x80 + column - 1); break;
  case 2: LCD_WriteCommand (0xc0 + column - 1); break;
  default: break;
 }
}