Uses bitmath to assess an 8 bit register of switches and notes any recently-depressed switches to toggle LED lights on a separate register of 8 bits...

toggle_led_bitmath.c

/*
 * toggle_led_bitmath.c
 * Description: Uses bitmath to assess an 8 bit register of switches
 *              and notes any recently-depressed switches to toggle
 *              LED lights on a separate register of 8 bits...
*/

#define F_CPU 16000000UL //Define the speed the clock is running at.  Used for the delay.h functions

#include <avr/io.h>     //Include the headers that handles Input/Output function for AVR chips
#include <util/delay.h> //Include the headers that allow for a delay function

//Prototypes
void Delay_ms(int cnt);
void init_io(void);

//Variables
int last_scan = 0;

//Functions
void Delay_ms(int cnt)
{
  while(cnt-->0) _delay_ms(1);
}

void init_io(void)
{
	DDRD = 0x00;    // Make port D all inputs
	DDRB = 0xFF;    // Make port B all outputs
	PORTB = 0xFF;   // Default port B outputs to OFF (pull-up resistors dictate that 1 is off and 0 is on...)
}

void f_switch_led(void)
{
}

//Main Function
int main(void)
{
  init_io(); //Set up the pins that control the LEDs

  for (;;)   //Loop forever
  {
  	int current_scan = PIND;
  	int current_changes_high_to_low = last_scan & ~current_scan;  // Which buttons have recently been released?
  	PORTB ^= current_changes_high_to_low;                         // Toggle the LED state of the buttons that have recently been released.
  	last_scan = current_scan;                                     // Retain the current button scan state for comparing next loop...

	  Delay_ms(40);   // Switch contact debounce
  }
}