How to set ISR to run every second - C Atmega328p

Question

I'm writing a code that needs to check a sensor's input every 0.5s. I want to use an ISR because I want my code to execute until the sensor's input changes.

How would I set up this ISR to execute every 0.5s?

Thanks :)

Answer 1

I would suggest using a Timer interrupt. For an example go here. http://www.avrfreaks.net/forum/tut-c-newbies-guide-avr-timers?page=all

I haven't tested it myself but here is a section of code on that.

#include 
#include 

int main (void)
{
   DDRB |= (1 << 0); // Set LED as output

   TCCR1B |= (1 << WGM12); // Configure timer 1 for CTC mode

   TIMSK |= (1 << OCIE1A); // Enable CTC interrupt

   sei(); //  Enable global interrupts

   OCR1A   = 15624; // Set CTC compare value to 1Hz at 1MHz AVR clock, with a prescaler of 64

   TCCR1B |= ((1 << CS10) | (1 << CS11)); // Start timer at Fcpu/64

   for (;;)
   {

   }
}

ISR(TIMER1_COMPA_vect)
{
   PORTB ^= (1 << 0); // Toggle the LED
}