/*
 counter.c
 Alexander Hiam

 Continually counts to 12 using 4 LEDs as a binary display 
 on an ATmega328p or compatible AVR using AVR-GCC.

 Compare to counter.ino
*/

#define F_CPU 16000000L

#include <avr/io.h>
#include <util/delay.h>

#define LED_DDR DDRB
#define LED_PORT PORTB
#define LED_MASK (0b1111 << 4)

#define RESET_TIMER (timer = 0)
int timer;

void delay(int ms) {
  int i;
  for (i=0; i<ms; i++) {
    _delay_ms(1);
  }
}

int main(void) {
  // Set LEDs as outputs:
  LED_DDR |= LED_MASK;
  RESET_TIMER;

  while(1) {
    // Set LEDs:
    LED_PORT = (LED_PORT & ~LED_MASK) | (timer & LED_MASK);
    timer++;
    if (timer > 12) RESET_TIMER;
    delay(1000);
  }
  return 1;
}