christmas light

main.c

#include <stdint.h>
#include <stdlib.h>
#include <avr/io.h>
#include <avr/sleep.h>
#include <avr/interrupt.h>

#include "light_ws2812.h"

#define FPS (33)
#define NUM_OF_LEDS (10)
// Soft limit, if more than this number of LEDs are on it won't reduce wait of
// others. But it might be that more LEDs are on if they are enabled in the same
// frame.
#define MAXIMUM_LEDS (NUM_OF_LEDS >> 1)
#define COUNTER (F_CPU / 1000 / 1024 * (1000 / FPS))
#define MAX_BRIGHTNESS (128)  // unused

struct cRGB vals[NUM_OF_LEDS];
uint8_t max[NUM_OF_LEDS];
int8_t delta[NUM_OF_LEDS];
uint8_t wait[NUM_OF_LEDS];
uint8_t active_leds = 0;

volatile uint8_t frame = 0;

int main(void)
{
    DDRB |= (1 << PB2);
    DDRD |= (1 << PD7) | (1 << PD6);

    set_sleep_mode(SLEEP_MODE_IDLE);

    uint8_t i;
    for (i = 0; i < NUM_OF_LEDS; i++)
    {
        vals[i].r = 0;
        vals[i].g = 0;
        vals[i].b = 0;
        max[i] = 0;
        delta[i] = 0;
        wait[i] = (uint8_t) rand();
    }

    OCR1A = COUNTER;
    TIMSK1 = (1 << OCIE1A);  // Interrupt on OCR1A overflow
    TCCR1A = 0;
    TCCR1B = (1 << WGM12) | (1 << CS12) | (1 << CS10);  // CTC mode and 1024 prescaler
    while (1)
    {
        PORTD &= ~(1 << PD6);
        for (i = 0; i < NUM_OF_LEDS; ++i)
        {
            if (wait[i] > 0)
            {
                if (active_leds <= MAXIMUM_LEDS)
                {
                    PORTD |= (1 << PD6);
                    wait[i]--;
                }
            }
            else
            {
                if (vals[i].r == 0)
                {
                    active_leds++;
                    max[i] = ((uint8_t) rand() & 0x3F) + 64;
                    delta[i] = (int8_t) ((rand() & 0x02) + 1);
                }
                if (delta[i] < 0 && vals[i].r <= delta[i])
                {
                    active_leds--;
                    vals[i].r = 0;
                    wait[i] = (uint8_t) rand();
                }
                else if (vals[i].r + delta[i] < max[i])
                {
                    vals[i].r += delta[i];
                }
                else
                {
                    vals[i].r = max[i];
                    wait[i] = (uint8_t) rand() & 0x0F;
                    delta[i] = -delta[i];
                }
            }
        }
        ws2812_setleds(vals, NUM_OF_LEDS);
        if (frame == 0)
        {
            PORTD &= ~(1 << PD7);
            sleep_mode();
        }
        else
        {
            PORTD |= 1 << PD7;
        }
        frame = 0;
    }
    return 0;
}

ISR(TIMER1_COMPA_vect)
{
    frame = 1;
}