#include <Arduino.h>
/*
Example code with timer interrupt that will create an interruption each 10ms using timer1 and prescalar of 256.
Calculations (for 10ms):
System clock 16 Mhz and Prescalar 256;
Timer 1 speed = 16Mhz/256 = 62.5 Khz
Pulse time = 1/62.5 Khz = 16us
Count up to = 10ms / 16us = 625 (so this is the value the OCR register should have)
*/
bool LED_STATE = true;
void setup() {
pinMode(13, OUTPUT); //Set the pin to be OUTPUT
cli(); //stop interrupts for till we make the settings
/*1. First we reset the control register to amke sure we start with everything disabled.*/
TCCR1A = 0; // Reset entire TCCR1A to 0
TCCR1B = 0; // Reset entire TCCR1B to 0
/*2. We set the prescalar to the desired value by changing the CS10 CS12 and CS12 bits. */
TCCR1B |= B00000100; //Set CS12 to 1 so we get prescalar 256
/*3. We enable compare match mode on register A*/
TIMSK1 |= B00000010; //Set OCIE1A to 1 so we enable compare match A
/*4. Set the value of register A to 31250*/
OCR1A = 625; //Finally we set compare register A to this value
sei(); //Enable back the interrupts
}
void loop() {
// put your main code here, to run repeatedly:
}
//With the settings above, this IRS will trigger each 500ms.
ISR(TIMER1_COMPA_vect){
TCNT1 = 0; //First, set the timer back to 0 so it resets for next interrupt
LED_STATE = !LED_STATE; //Invert LED state
digitalWrite(13,LED_STATE); //Write new state to the LED on pin D5
}