Can i hang into interrupt 0 used by standard timing functions like millis()

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1

Hello,

interrupt 0 ist used by Arduino standard timing functions like millis().
Can i hang into this interrpt routine, to start an action in my program every ms?

Of course i could use the other timers, but i run out of available timers on my mini pro.

My idea is using standard timer 0 interrupt routine with OCR2A register.
Is OCR2A used bei standard routines?

SIGNAL(TIMER0_COMPA_vect)
{
// do something
}

regards

2

Which MCU, ATmega328P? (BTW the SIGNAL is obsolete, use the ISR)
I'm not sure what you are asking. Do not mess interrupt 0 and timer 0 interrupt. The millis() uses TIMER0_OVF. Even though the TIMER0_COMPA is different vector, counter register for COMPA, COMPB and OVF is common and can be affected by each other. As an example, in CTC mode counter register is cleared to zero as it matches OCR, but for the millis() and its correct functionality cyclic overflow of counter is required.

3

You can use the compa vector as long as you dont fiddle with the timer configuration - but the millis timer doesnt overflow exactly once per ms, its slightly slower than that, and i think its a mode where it counts up and back down, so i think you get a compare maych twice per cycle

Read out the timer registers for timer zero, print to serial, and crossreference with datasheet.