/*  Name     : main.c
 *  Purpose  : Source code for LDR Interfacing with PIC18F4550.
 *  Author   : Gemicates
 *  Date     : 2017-07-03
 *  Website  : www.gemicates.org
 *  Revision : None
 */

#include<htc.h>
#define _XTAL_FREQ 12000000                // 12MHZ

#define LDR PORTA

void LDR_Init()
{
  ADCON0 = 0x41;                           // ADC Module Turned ON and Clock is selected
  ADCON1 = 0xC0;                           // All pins as Analog Input
                                           // With reference voltages VDD and VSS
}

unsigned int LDR_Read(unsigned char channel)
{
  if(channel > 7)                          // If Invalid channel selected 
    return 0;                              // Return 0

  ADCON0 &= 0xC5;                          // Clearing the Channel Selection Bits
  ADCON0 |= channel<<3;                    // Setting the required Bits
  __delay_ms(2);                           // Acquisition time to charge hold capacitor
  GO_nDONE = 1;                            // Initializes A/D Conversion
  while(GO_nDONE);                         // Wait for A/D Conversion to complete
  return ((ADRESH<<8)+ADRESL);             // Returns Result
}

void main()
{
  unsigned int a;
  
  TRISC= 0xC0;                             // PORTC as output
  LDR = 0xFF;                              // PORTA as input
  LDR_Init();                              // Initializes LDR Module

  do
  {
    a = LDR_Read(0);                       // Reading Analog Channel 0
    PORTC = a>>8;                          // Higher 2 bits to PORTC
    __delay_ms(60);                        // Delay
  }while(1);                               // Infinite Loop
}