/* Exercise 10.3 Automatic night light  */
/* Needs Port A pin 0 as an analogue input */
/* Created David Miles April 2006 */
/* Updated Ben Rowland Febuary 2014 */

#include <xc.h>

// CONFIG1
#pragma config FOSC = HS        // Oscillator Selection (HS Oscillator, High-speed crystal/resonator connected between OSC1 and OSC2 pins)
#pragma config WDTE = OFF       // Watchdog Timer Enable (WDT disabled)
#pragma config PWRTE = OFF      // Power-up Timer Enable (PWRT disabled)
#pragma config MCLRE = ON       // MCLR Pin Function Select (MCLR/VPP pin function is MCLR)
#pragma config CP = OFF         // Flash Program Memory Code Protection (Program memory code protection is disabled)
#pragma config CPD = OFF        // Data Memory Code Protection (Data memory code protection is disabled)
#pragma config BOREN = ON       // Brown-out Reset Enable (Brown-out Reset enabled)
#pragma config CLKOUTEN = OFF   // Clock Out Enable (CLKOUT function is disabled. I/O or oscillator function on the CLKOUT pin)
#pragma config IESO = OFF       // Internal/External Switchover (Internal/External Switchover mode is disabled)
#pragma config FCMEN = OFF      // Fail-Safe Clock Monitor Enable (Fail-Safe Clock Monitor is disabled)

// CONFIG2
#pragma config WRT = OFF        // Flash Memory Self-Write Protection (Write protection off)
#pragma config VCAPEN = OFF     // Voltage Regulator Capacitor Enable (All VCAP pin functionality is disabled)
#pragma config PLLEN = OFF      // PLL Enable (4x PLL disabled)
#pragma config STVREN = ON      // Stack Overflow/Underflow Reset Enable (Stack Overflow or Underflow will cause a Reset)
#pragma config BORV = LO        // Brown-out Reset Voltage Selection (Brown-out Reset Voltage (Vbor), low trip point selected.)
#pragma config LVP = OFF        // Low-Voltage Programming Enable (High-voltage on MCLR/VPP must be used for programming)

#define _XTAL_FREQ 19660800	// Defines the hardware crystal frequency allowing the delay function to work correctly

#define THRESHOLD 500


void setup_hardware (void)
{
    ANSELA = 0x01;              //Set PortA to use digital inputs RA0 is analogue
    ANSELB = 0x00;
    TRISA = 0xF1;               //PORTA bits 1-3 set to outputs
    TRISB = 0x00;               //PORTB set to all outputs
    ADCON0 = 0x00;              //Select A0 for analogue input
    ADCON1 = 0xF0;              //Set for right justified value and FRC conversion speed

    LATA = 0;
    LATB = 0;
}


int read_adc0 ( void )
{
    unsigned char h, l ;
    int result;

    ADCON0 = 0x01;              //enable the converter
    ADCON0 = 0x03;              //start the conversion

    while ( ADCON0 & 0x02 );    //wait here while the conversion runs

    h = ADRESH;                 //read the high byte
    l = ADRESL;                 //read the low byte

    result = (256 * h) + l;     //return the result
    return result;
}


int main (void)
{
    int v;
    setup_hardware ();

    while (1) 
    {
        v = read_adc0();

        if ( v < THRESHOLD )
        {
            LATB = 255;
        }
        else
        {
            LATB = 0;
        }
    }

    return 0;
}