Timer0 stop working after wakeup from power_down sleep

[garudaonekh]

Hi, I use the following code to go power_down sleep. However, after wakeup from INT0 interrupt, the millis() function return the same value in the loop. It's based on Timer0 so I guess Timer0 must stop working.

#include <avr/io.h>
#include <avr/sleep.h>
#include <avr/interrupt.h>
#include <util/delay.h>

void setup()
{
   DDRC |= (1 << PC2) | (1 << PC1);     // leds for testing

   DDRD &= ~(1 << PD2);    // INT0: input...
   PORTD |= (1 << PD2);    // ...with pullup.

   // level interrupt INT0 (low level)
   MCUCR &= ~((1 << ISC01) | (1 << ISC00));

   // infinite main loop

}
void loop(){
      // trigger leds for testing
      PORTC ^= (1 << PC1);
      _delay_ms(500);
      PORTC ^= (1 << PC1);

      // enable external interrupt
      GICR |= (1 << INT0);

      // set sleep mode
      set_sleep_mode(SLEEP_MODE_PWR_DOWN);

      // sleep_mode() has a possible race condition
      sleep_enable();
      sei();
      sleep_cpu();
      sleep_disable();

      // waking up...
      // disable external interrupt here, in case the external low pulse is too long
      GICR &= ~(1 << INT0);

      // disable all interrupts
      cli();
}

ISR(INT0_vect)
{
   // ISR might be empty, but is necessary nonetheless
   PORTC ^= (1 << PC2);    // debugging
}

[MCUdude]

Timer 0 is by default used for millis/micros(), and is initialized before setup(). it is bein initialised in the init() function:

https://github.com/MCUdude/MightyCore/blob/b360c00e41c494731e2898aaa3afd778f748f3e3/avr/cores/MCUdude_corefiles/main.cpp#L33-L51

If you want to run code natively, without the Arduino framework, ditch setup() and loop() in your sketch, and use this instead:

#include <avr/io.h>
#include <avr/sleep.h>
#include <avr/interrupt.h>
#include <util/delay.h>

int main() {
    DDRC |= (1 << PC2) | (1 << PC1);     // leds for testing

    DDRD &= ~(1 << PD2);    // INT0: input...
    PORTD |= (1 << PD2);    // ...with pullup.

    // level interrupt INT0 (low level)
    MCUCR &= ~((1 << ISC01) | (1 << ISC00));  

    while(1) {
        // trigger leds for testing
        PORTC ^= (1 << PC1);
        _delay_ms(500);
        PORTC ^= (1 << PC1);

        // enable external interrupt
        GICR |= (1 << INT0);

        // set sleep mode
        set_sleep_mode(SLEEP_MODE_PWR_DOWN);

        // sleep_mode() has a possible race condition
        sleep_enable();
        sei();
        sleep_cpu();
        sleep_disable();

        // waking up...
        // disable external interrupt here, in case the external low pulse is too long
        GICR &= ~(1 << INT0);

        // disable all interrupts
        cli();
    }
}

ISR(INT0_vect)
{
   // ISR might be empty, but is necessary nonetheless
   PORTC ^= (1 << PC2);    // debugging
}

[garudaonekh]

I don't get you. My problem is millis() return the same value after my above code wakeup from INT0 interrupt. My guess is that my deep sleep code disable the TImer0.

[MCUdude]

SLEEP_MODE_POWER_DOWN stops timer0 as well:

https://onlinedocs.microchip.com/pr/GUID-A834D554-5741-41A3-B5E1-35ED7CD8250A-en-US-5/index.html?GUID-825A28EE-C4E4-4C03-864F-92AA9BA41231

[garudaonekh]

Yes, but when wakeup from PIN interrupt, the loop() run as usual but timer0 still not working. I also call sleep_disable() but still not working.

[garudaonekh]

At sei() after wakeup solved the problem.