#include <stdlib.h>
#include <xc.h>

#pragma config FOSC = INTRCIO   // INTOSC: I/O function on GP4/5
#pragma config WDTE = OFF       // Watchdog Timer
#pragma config PWRTE = OFF      // Power-Up Timer
#pragma config MCLRE = ON       // MCLR external control
#pragma config BOREN = OFF      // Brown-out Detect
#pragma config CP = OFF         // Program memory code Protection
#pragma config CPD = OFF        // Data memory code protection

#define PWM_STEPS 16
#define STATIC_REPEATS 4
#define LED_NUM 3

// Timeout to start dimming
// Each 1K is ~7.5 seconds
#define MAX_CYCLES 10000
// Timeout for dim step
#define DIM_COUNT 200

struct tLED {

    char brightness;
    char pinBinary;
    
} LED[LED_NUM];

void initLEDs() {

    char j;
    for (j = 0; j < LED_NUM; j++) {
        LED[j].brightness = 0;
    }

    LED[0].pinBinary = 4; // GP2
    LED[1].pinBinary = 16; // GP4
    LED[2].pinBinary = 32; // GP5
}

void initRegisters() {

    ANSEL = 0; // All pins Digital
    TRISIO = 0; // All pins output
    CMCON = 7; // Comparator off
    ADCON0 = 0; //A/D conversion off
    GPIO = 0; // Outputs LOW

}

void main() {

    char j;
    unsigned char r, pwmStep, pattern;
    unsigned char randResult;
    
    unsigned int cycleCount = 0;
    char highPWM = PWM_STEPS;

    initRegisters();
    initLEDs();

    while (1) {

        randResult = rand();
        for (j = 0; j < LED_NUM; j++) {

            switch (randResult & 3) {
                case 1: if (LED[j].brightness < highPWM)
                          LED[j].brightness++;
                        break;
                case 2: if (LED[j].brightness > 0)
                          LED[j].brightness--;
                        break;
            } // switch
            randResult >>= 2;

        } // for

        for (r = 0; r < STATIC_REPEATS; r++)
            for (pwmStep = 0; pwmStep < PWM_STEPS; pwmStep++) {

                pattern = 0;
                for (j = 0; j < LED_NUM; j++) 
                    if (LED[j].brightness > pwmStep) pattern |= LED[j].pinBinary;
                GPIO = pattern;

            } // for

        cycleCount++;

        // Are we in the dimming phase?
        if (highPWM < PWM_STEPS) {

            if (cycleCount == DIM_COUNT) {
              cycleCount = 0;
              highPWM--;
              if (!highPWM) break;
            }

        } else if (cycleCount == MAX_CYCLES) {
            // Switch to dimming mode
            highPWM--;
            cycleCount = 0;
           }

    } // while

    asm("sleep");

} // main