Can we use millis in an interrupt?

Projects Programming
1

Hello

I ma actually working on Davis anemometer following that tuto

I am surprised to see a millis in an interrupt, I was sure that a millis can not used in a intterrupt.

It's works but is it reliable?

Cheers

2

Why do you think it can't be used?

It's important to know.

3

Yes, it works fine.

If your interrupt function lasts more than a millisecond, millis() won't update. That should not be a problem though.

4

You can use millis() in an ISR but its value will not change whilst in an ISR. Not that an ISR should last that long anyway

5

taking snapshots of millis() or micros() is no problem
using them for timing might be a problem if you are doing it in a blocking way.

I looked up the code

it is doing

void isr_rotation () {

if ((millis() - ContactBounceTime) > 15 ) { // debounce the switch contact.
Rotations++;
ContactBounceTime = millis();
}
}

it does just a checking but no delay. Anyway timing based on millis() is non-blocking so the isr runs through as fast as possible. A delay would do what its name says delay.

the isr above does its check and that's all

best regards Stefan