Can't wake up ATtiny4313

Hey Guys !

I am working on a small led display project. I am using an ATtiny 4313-PU. I have a code to send the unit to sleep. I wood like the unit to come back to life when I press a button on the INT0 interrupt pin.

Do you have any idea what I am doing wrong ?

Thanks for your help !!

#include <avr/interrupt.h>
#include <avr/sleep.h>
#include <avr/power.h>
#include <avr/io.h> 

uint8_t led = 0;

void setup() {
  
  pinMode(7, OUTPUT);
  pinMode(6, OUTPUT);
  
  cli();
  GIMSK |=  (1<<INT0); //activate INT0 interupt
  MCUCR |= (0<<ISC00); //falling edge
  MCUCR |= (1<<ISC01);
  sei();
}

void loop() {
  delay(1000);
  sleepNow();
}

void sleepNow()
{
    // Choose our preferred sleep mode:
    set_sleep_mode(SLEEP_MODE_PWR_DOWN);
 
    // Set sleep enable (SE) bit:
    digitalWrite(6, LOW);   // turn the LED on (HIGH is the voltage level)
    //delay(1000);
    sleep_enable();
 
    // Put the device to sleep:
    sleep_mode();
 
    // Upon waking up, sketch continues from this point.
    sleep_disable();
    digitalWrite(6, HIGH);    // turn the LED off by making the voltage LOW
    delay(5000);
}

ISR(INT0_vect)
{
  static unsigned long last_interrupt_time = 0;
  unsigned long interrupt_time = millis();
  // If interrupts come faster than 200ms, assume it's a bounce and ignore
  //if (interrupt_time - last_interrupt_time > 200) 
  //{
    cli();
    led = !led;
    digitalWrite(7, led);
    delay(1000);
    sei();
 //}
 last_interrupt_time = interrupt_time;
}

INT0 pin is pulled down

"delay" needs interrupts to be enabled. Interrupts are disbbled inside ISR by default unless enabled by software.

So probably your debouncing inside ISR makes the problem.

Hi! Thanks for your feedback !

I've tried loading the program without the delay function and I have the same problem..

Maybe I should switch to avr studio and use the debugger. I am still interested in any other proposition though :slight_smile:

Thanks!!

Is INT0 being pulled up, and then brought low? I would doublecheck that that pin is starting out high and being brought low (not just held low).

The delay was wrong.
"sei" should not be called inside ISR unless you KNOW what you are doing (reentrant code etc.)
And most importantly: you cannot detect edge triggered interrupts while clock is not running - in power down mode! Change it to level interrupt.

Hey guys !

Thank you so much ! I tried making it work with the level interrupt and it worked !

Previously the INT0 pin was pulled down and pulled up during interrupt. Why could this be a problem ?

TIMOT05:
Previously the INT0 pin was pulled down and pulled up during interrupt. Why could this be a problem ?

Logic detecting edge interrupt needs IO clock running. Power down mode stops this clock (and most of others).