adc.c

#include <xc.h>
#include "adc.h"

void init_adc(void)
{
    /* Selecting right justified ADRES Registers order */
    ADFM = 1;

    /* 
     * Acqusition time selection bits 
     * Set for 8 Tad
     */
    ACQT2 = 1;
    ACQT1 = 0;
    ACQT0 = 0;

    /*
     * Selecting the conversion clock of Fosc / 32 -> 1.6usecs -> 1Tad
     * Our device frequency is 20 MHz
     */
    ADCS0 = 0;
    ADCS1 = 1;
    ADCS2 = 0;

    /* Stop the conversion to start with */
    GODONE = 0;

    /* Selecting the channel */
    CHS2 = 1;

    /* Voltage reference bit as VSS */
    VCFG1 = 0;
    /* Voltage reference bit as VDD */
    VCFG0 = 0;

    /* Just clearing the ADRESH & ADRESL registers, for time pass */
    ADRESH = 0;
    ADRESL = 0;

    /* Turn ON the ADC module */
    ADON = 1;
 
}

unsigned short read_adc(unsigned char channel)
{
    unsigned short reg_val;

    ADCON0 = (ADCON0 & 0xc3) | (channel << 2);
    /* Start the conversion */
    GO = 1;
    while (GO);
    reg_val = (ADRESH << 8) | ADRESL; 

    return reg_val;
}