Sleep and wake up on ext. interrupt not working

[leozulfiu]

The Problem

I would like to put the atmega328pb to sleep and wake up again when pressing a button which is connected to an external interrupt pin. I tried it with the attached sketch but it doesn't work really stable.

Observations

• When I press the button during the counting up (awake phase) the variable count is increased with each button push. IMO pressing the button shouldn't affect the loop execution at all.
• Holding down the button during the loop execution and following sleep phase results in a microcontroller deadlock. It becomes completly unresponsive and a new upload of the sketch is needed.

Example Code

#include <avr/sleep.h>

int wakePin = 2;
int sleepStatus = 0;
int count = 0;

void wakeUpNow() {
  detachInterrupt(0);
}

void setup() {
  pinMode(wakePin, INPUT);
  Serial.begin(9600);
  attachInterrupt(0, wakeUpNow, LOW);
}

void sleepNow() {
    set_sleep_mode(SLEEP_MODE_PWR_DOWN);
    sleep_enable();
    attachInterrupt(0, wakeUpNow, LOW);
    sleep_mode();

    sleep_disable();
}

void loop() {
  Serial.print("Awake for ");
  Serial.print(count);
  Serial.println("sec");
  count++;
  delay(1000);

  if (count >= 5) {
      Serial.println("Timer: Entering Sleep mode");
      Serial.flush();
      delay(100);

      count = 0;
      sleepNow();
  }
}

[leozulfiu]

I added another println statement (Serial.println("In setup method");) in the setup method to debug the issue and found out that the microcontroller is restarting itself after each sleep cycle. Is this a bug or an issue with my sketch?

[awatterott]

I have tested your program with IDE 1.8.5 + AVR Boards 1.6.206 and it is working. I have only activated the pull-up on pin 2.

void setup() {
  pinMode(wakePin, INPUT);
  digitalWrite(wakePin, HIGH);