/*
  timer_demo3.c

  Use of timer0 to produce a regular event (in this example, the
  toggling of an output pin).  This happens while we also do "something
  else".

  With a 16MHz clock, timer0 increments every 64/16000000 seconds,
  which is 4 usec.  The SIG_OVERFLOW0 interrupt occurs every
  (64*256)/16000000 = 0.001 seconds.  On each interrupt, the routine
  increments an internal counter ("counter").  When this counter reaches
  26, the interrupt routine sets trigger_flag and resets "counter".
  26 * 0.0010 sec = 26.6 msec.  So - trigger_flag is set to 1 at 37.561 Hz.


*/


#include <avr/io.h>
#include <avr/signal.h>
#include <avr/interrupt.h>
#include <stdio.h>
#include "oulib.h"

// Global so that it can be used in the interrupt handler, but
//  initialized by the  main routine.

volatile uint8_t trigger_flag;

// Interrupt handler for TIMER0 overflow
ISR(TIMER0_OVF_vect) {
  static unsigned char counter = 0;
  ++counter;

  if(counter == 26) {
    // Toggle output state every 61st interrupt:
    //  This means on for ~ 1 second and then off for ~1 sec
    trigger_flag = 1;
    counter = 0;
  };
};

int main(void) {
  // Interrupt occurs every (64*256)/16000000 = .0010 seconds
  timer0_config(TIMER0_PRE_64);
  // Enable the timer interrupt
  timer0_enable();
  // Enable global interrupts 
  sei();

  while(1) {
    while(trigger_flag == 0) {}
    trigger_flag = 0;
    // Sample from the sensors (result is 37.5601 Hz)
    
  };

  return(0);
}