HW_LAB_4_1 (draft)

/**
 * program to change brightness of an LED
 * demonstration of PWM
*/

‪#‎include‬ <avr/io.h>
#include <util/delay.h>
// ‪#‎define‬ F_CPU 16000000UL

// initialize PWM
void pwm_init() {
	// initialize timer0 in PWM mode
	TCCR0A |= (1<<WGM00)|(1<<WGM01)|(1<<WGM02)|(1<<COM0A1)|(1<<COM0A0)|(1<<CS00);
	TCCR0B |= (1<<WGM00)|(1<<WGM01)|(1<<WGM02)|(1<<COM0A1)|(1<<COM0A0)|(1<<CS00);

	// make sure to make OC0 pin (pin PB2 for atmega168) as output pin
	DDRB |= (1 << PB1);
	PORTB |= (1 << PB1);
	DDRB |= (1 << PB2);
}

int main() {
	unsigned int brightness;

	// initialize timer0 in PWM mode
	pwm_init();

	// run forever
	while(1) {
		// increasing brightness
		for (brightness = 0; brightness < 30; ++brightness) {
			// set the brightness as duty cycle
			// delay so as to make the user "see" the change in brightness
			OCR0A = brightness;
			PORTB |= (1 << PB2);
			_delay_ms( 30 - brightness );
			PORTB ^= ~(1 << PB2);
			_delay_ms( brightness );
		}

		// decreasing brightness
		for (brightness = 30; brightness > 0; --brightness) {
			// set the brightness as duty cycle
			// delay so as to make the user "see" the change in brightness
			OCR0A = brightness;
			PORTB |= (1 << PB2);
			_delay_ms( brightness );
			PORTB ^= ~(1 << PB2);
			_delay_ms( 30 - brightness );
		}

		// repeat this forever
	}
}