/* Written 2007 
   by Matthias Bolte and Aiko Christ*/

#include <avr/io.h>
#include <avr/iotn2313.h>
#include <avr/interrupt.h>
#include <stdint.h>

#define DDB0 0
#define DDB1 1
#define DDB2 2

#define PB0 0
#define PB1 1
#define PB2 2

typedef struct pwm_global_s {
	uint8_t cycles;
} pwm_global_t;

typedef struct pwm_led_s {
	uint8_t offcycles;
	uint8_t port;
} pwm_led_t;

typedef struct fade_s {
	uint8_t cur;
	uint8_t dir[3];
	uint8_t speed[3];
} fade_t;

// define and init struct
pwm_global_t pwm_global = {0};
pwm_led_t pwm_led[3] = {{255,PB0},{96,PB1},{128,PB2}};
fade_t fade = {0,{0,0,0},{2,1,2}};

void pwm_handler() {
	pwm_led_t* led;
	uint8_t i;

	for (i=0;i<3;++i) {
		led = &pwm_led[i];

		if (!pwm_global.cycles && led->offcycles != 0) {
			PORTB &= ~(1 << led->port);
		}
		else if (pwm_global.cycles == led->offcycles && led->offcycles < 255){
			PORTB |= (1 << led->port);
		}
	}
}

void fade_handler() {
	pwm_led_t* led_p;
	fade_t* fade_p;
	uint8_t speed;
	uint8_t i;

	for (i=0;i<3;++i) {
		led_p = &pwm_led[i];
		fade_p = &fade;

		speed = fade_p->speed[i];

		if (fade_p->dir[i] == 1) {
			if (led_p->offcycles > speed - 1)
				led_p->offcycles -=  speed;
			else {
				led_p->offcycles +=  speed;
				fade_p->dir[i] = 0;
			}
		}
		else {
			if (led_p->offcycles < 256 - speed)
				led_p->offcycles +=  speed;
			else {
				led_p->offcycles -=  speed;
				fade_p->dir[i] = 1;
				fade_p->cur = (fade_p->cur + 1) % 3;
			}
		}
	}
}

ISR(TIMER1_COMPA_vect) {
	++pwm_global.cycles;

	if (!pwm_global.cycles)
		fade_handler();

	pwm_handler();
}

int main(void) {	
	DDRB |= (1 << DDB0) | (1 << DDB1) | (1 << DDB2);

	TCCR1A = 0;
	TCCR1B = (1 << WGM12) | (1 << CS10);

   	OCR1A = (unsigned short) ((unsigned long) 1024 + 256);
    TIMSK |= (1 << OCIE1A);

	sei();

	while(1) {
	}
	
	return 0;
}