For my blog: thepiandi.blogspot.com Demonstrates ATmega register programming to tuirn Gertboard LEDs on and off in sequence

IOPosts_Output2LEDs.ino

#include <avr/io.h>

void setup(){
  // PB0, PB1, PB2, PB3, PB4, PB5 connect to LEDs so must be outputs
  DDRB = 0b00111111;
  // All LEDs off 
  PORTB = 0X00; 
}

void loop(){
  // Turn LED at PB0 on
  PORTB |= (1 << PORTB0); 
  delay(1000);
  // Turn LED at PB0 off, LED at PB1 on
  PORTB &= ~(1 << PORTB0);
  PORTB |= (1 << PORTB1); 
  delay(1000);
  // Turn LED at PB1 off, LED at PB2 on
  PORTB &= ~(1 << PORTB1);
  PORTB |= (1 << PORTB2); 
  delay(1000);
  // Turn LED at PB2 off, LED at PB3 on
  PORTB &= ~(1 << PORTB2);
  PORTB |= (1 << PORTB3); 
  delay(1000);
  // Turn LED at PB3 off, LED at PB4 on
  PORTB &= ~(1 << PORTB3);
  PORTB |= (1 << PORTB4); 
  delay(1000);
  // Turn LED at PB4 off, LED at PB5 on
  PORTB &= ~(1 << PORTB4);
  PORTB |= (1 << PORTB5); 
  delay(1000);
  // Turn LED at PB5 off
  PORTB &= ~(1 << PORTB5);
}