// Port IO Example
#include <avr/io.h>
// Input Port pin SWITCH_IP
#define PORT_SWITCH_IP  PORTB
#define DDR_SWITCH_IP   DDRB
#define PIN_SWITCH_IP   PINB
#define BIT_SWITCH_IP   5
// Output Port pin LED_O
#define PORT_LED_O      PORTB
#define DDR_LED_O       DDRB
#define BIT_LED_O       6

int main(void)
{
    // Set LED_O as output pin
    DDR_LED_O |= (1<<BIT_LED_O);
    // Set SWITCH_IP as input pin
    DDR_SWITCH_IP &= ~(1<<BIT_SWITCH_IP);
    // Enable pull-up on SWITCH_IP
    PORT_SWITCH_IP |= (1<<BIT_SWITCH_IP);
    // Repeat indefinitely
    for(;;)
    {
        // See if switch is pressed
        if((PIN_SWITCH_IP&(1<<BIT_SWITCH_IP)) == 0)
        {
            // Enable LED
            PORT_LED_O |= (1<<BIT_LED_O);
        }
        else
        {
            // Disable LED
            PORT_LED_O &= ~(1<<BIT_LED_O);
        }
    }
}