Richards-MacBook-Pro:src richard$ cat main.c
/*
* Hackaday.com AVR Tutorial firmware
* written by: Mike Szczys (@szczys)
* 10/24/2010
*
* ATmega168
* Blinks one LED conneced to PD0
*
* http://h...content-available-to-author-only...y.com/2010/10/25/avr-programming-02-the-hardware/
*/
 
#include <avr/io.h>
#include <avr/interrupt.h>
 
int main(void)
{
 
  //Setup the clock
  cli();			//Disable global interrupts
  TCCR1B |= 1<<CS11 | 1<<CS10;	//Divide by 64
  OCR1A = 15624;		//Count 15624 cycles for 1 second interrupt
  TCCR1B |= 1<<WGM12;		//Put Timer/Counter1 in CTC mode
  TIMSK1 |= 1<<OCIE1A;		//enable timer compare interrupt
  sei();			//Enable global interrupts
 
  //Setup the I/O for the LED
 
  DDRD |= 0xff; //(1<<0);		//Set PortD Pin0 as an output
  PORTD = 0;
 
  while(1) { }			//Loop forever, interrupts do the rest
}
 
ISR(TIMER1_COMPA_vect)		//Interrupt Service Routine
{
  PORTD += 1; // (1<<0);		//Use xor to toggle the LED
}

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