AVR Microcontroller Advanced Hello World (LED Blink) http://youtu.be/KatkY_YJgsY

gistfile1.cpp

#define F_CPU 16000000 //16MHz
#include <avr/io.h>
#include <util/delay.h>

int ledPins[] = {PC3, PC4, PC5};
int ledPinsNum = sizeof(ledPins)/sizeof(int);


bool pressed = false;
bool oldPressed = false;
bool leftDirection = false;

bool button_is_pressed()
{
	//debouncing
	if(bit_is_clear(PINC, PC2))
	{
		_delay_ms(10);
		if(bit_is_clear(PINC, PC2))
		{
			return true;
		}
	}
	
	return false;
}

bool process_button()
{
	bool isChanged = false;
	
	pressed = button_is_pressed();
	
	isChanged = pressed && oldPressed == false;
	
	if(isChanged)
	{
		leftDirection = !leftDirection;
	}
	
	oldPressed = pressed;
	
	return isChanged;
}

void switch_off_leds()
{
	//drive all led pins low
	for(int i=0; i < ledPinsNum; i++)
	{
		PORTC &= ~(1<<ledPins[i]);
	}
}

int main(void)
{
	DDRC |= (1<<DDC3)|(1<<DDC4)|(1<<DDC5); // set PC3, PC4 and PC5 pins to output
	DDRC &= ~(1<<DDC2); // set PC2 pin to input
	PORTC |= (1<<PC2); //internal pull-up resistor for PC2
	
	int i=0;
	while(1)
	{
		bool buttonProcessed = false;
		switch_off_leds();
			
		//change the direction if necessary
		int currLedPin = leftDirection ?  ledPinsNum - i - 1: i;
			
		PORTC |= (1<<ledPins[currLedPin]); //drive current led pin high
			
		//500ms delay and button state reading
		for(int j=0; j < 10; j++)
		{
			//if the direction was changed, keep delaying without button state reading
			if(!buttonProcessed)
			{
				buttonProcessed = process_button();
			}
			
			_delay_ms(50);
		}			

		if(!(buttonProcessed && i==0))
		{
			i++;
		}
		
		if(i >= ledPinsNum)
		{
			i=0;
		}		
	}
}