// PIC18 in C - Versione 0.1 - Ottobre 2014
// Copyright (c) 2014, Vincenzo Villa
// Creative Commons | Attribuzione-Condividi allo stesso modo 3.0 Unported.
// Creative Commons | Attribution-Share Alike 3.0 Unported
// https://www.vincenzov.net/tutorial/PIC18/adc.htm

// Reference: PIC18F14K50 data sheet
//            IMPORTANT: PIC18(L)F1XK50 Silicon Errata - 9.1 Will not Start A/D Conversion

#include "configurationbits.h"

#define TIMER1_VALUE 1199 // T1 count from 0 to 1199 (1200 count => 10 KHz @ FCLK = 48 MHz, no prescaler)

void display(unsigned voltage);

void interrupt __high_priority my_isr_high(void) {

    /* This is a work around for bugged chip - See text
      if (PIR1bits.CCP1IF == 1) // Interrupt from ECCP ?
    {
        ADCON0bits.GO = 1; // Start conversion
        PIR1bits.CCP1IF = 0; // Clear interrupt status
    } 
     */
    if (PIR1bits.ADIF) // Interrupt from ADC?
    {
        display(ADRESH); // Display data from ADC
        PIR1bits.ADIF = 0; // Clear interrupt status
    }
}

void main(void) {

    TRISC = 0x00; // Set PORTC as output

    // Configure ADC and analog port
    TRISBbits.RB5 = 1; // Disable digital output buffer on AN11/RB5
    ANSELHbits.ANS11 = 1; // Disable digital input buffer for AN11
    ADCON0bits.CHS = 0b1011; // Analog Channel Select AN11
    ADCON2bits.ADFM = 0; // AD values left justified
    ADCON2bits.ADCS = 0b110; // AD Conversion Clock = FOSC/64 (1.33 us @ 48 MHz)
    ADCON2bits.ACQT = 0b001; // AD Acquisition time set to 2 TAD
    ADCON1 = 0; // Set VDD and VSS as voltage reference
    ADCON0bits.ADON = 1; //  Power ON ADC

    // Configure CCP1
    CCP1CONbits.CCP1M = 0b1011; // Compare mode, trigger special event
    CCPR1H = (TIMER1_VALUE & 0xFF00) >> 8; // Set compare registers - H
    CCPR1L = (TIMER1_VALUE & 0xFF); // Set compare registers - L
    T3CONbits.T3CCP1 = 0; // Timer1 is the clock source for compare

    // Configure Timer 1
    T1CONbits.T1OSCEN = 0; // Timer1 oscillator is shut off (not used - Free RC0, RC1 pin)
    T1CONbits.TMR1CS = 0; // Internal clock (FOSC/4)
    T1CONbits.T1CKPS = 0b00; // 1:1 Prescale value
    T1CONbits.TMR1ON = 1; // Enables Timer1

    // Configure interrupt
    RCONbits.IPEN = 1; // Enable priority levels on interrupts

    PIE1bits.ADIE = 1; // Enable interrupt from ADC
    IPR1bits.ADIP = 1; // ADC Interrupt Priority set to high
    PIR1bits.ADIF = 0; // Clear interrupt status to avoid automatic interrupt ad "boot time"

    PIE1bits.CCP1IE = 0; // Disable interrupt from CCP1 (default)
    // PIE1bits.CCP1IE = 1; // Enable interrupt from CCP1 - This is a work around for bugged chip - See text
    // IPR1bits.CCP1IP = 1; // CCP1 Interrupt Priority set to high
    // PIR1bits.CCP1IF = 0; // Clear interrupt status to avoid automatic interrupt ad "boot time"

    INTCONbits.GIE = 1; // Enables all interrupts

    while (1); // Do nothing, forever
}

void display(unsigned voltage) { // Display data on 8 LED - "VuMeter" like

    voltage = voltage + 16;
    voltage = (voltage >> 5);
    PORTC = ~(0xFF << voltage);
}