/*
	Rudolph the red nosed reindeer breathing LED
	Atmel Studio 7 C Code for the PCBWay Christmas 2017 surprise kit 
	(ATtiny85, 128KHz internal oscillator)
	Share and enjoy!
*/

// This must be at most 254
#define PWM_STEPS 64U

#define F_CPU 32000UL

#include <avr/io.h>
#include <util/delay.h>

void setup(void) {
	
	// Rudolph's nose is on PB0
	DDRB = 1;
	// Set clock prescaler 1:4
	// Unlock...
	CLKPR = (1 << CLKPCE);
	// Set
	CLKPR = 2;
	
}

void pwmCycle(uint8_t onTime) {
	
	uint8_t offTime = PWM_STEPS - onTime;
	while (offTime--) {
		PORTB &= ~1;
	}
	while (onTime--) {
		PORTB |= 1;
	}
	
}


int main(void)
{
	uint8_t x = 0;

    setup();
	
    while (1) {
		
		for (x = 0; x < PWM_STEPS; ++x) {
			pwmCycle(x);
		} 

		for (--x; x < PWM_STEPS; --x) {
			pwmCycle(x);
		}
		
		_delay_ms(1000);
		
    }
}