attiny85 reset itself instead of wakeup procedure

Question

I have a digispark attiny85, and I am using SLEEP_MODE_PWR_DOWN to sleep, and wake-up with external interrupt on pin2. I am trying to count number of interrupts received with the code below.

Problem is on every LOW signal on pin2, attiny85 reset (restart) itself instead of processor wake-up and continue where it left. I can identify this by seeing led blink 3 times(as in setup()) on every LOW signal.

Is there a limitation on this hardware? How can I only wake-up from sleep and not reset? I appreciate if you direct me an example.

#include <avr/interrupt.h>
#include <avr/sleep.h>
//modified from http://playground.arduino.cc/Learning/arduinoSleepCode
int ledPin = 0; // LED connected to digital pin 0
int interruptPin = 1; // LED to show the action of a interrupt
int wakePin = 2; // active LOW, ground this pin momentary to wake up
unsigned int counter = 0;
void setup(){
 pinMode(ledPin, OUTPUT); // sets the digital pin as output
 pinMode(interruptPin, OUTPUT); // sets the digital pin as output
 pinMode(wakePin, INPUT_PULLUP); // sets the digital pin as input
 digitalWrite(wakePin, HIGH);
 counter = 0;
 //do some blinks so we can identify boot & loop
 digitalWrite (interruptPin, HIGH); // sets the digital pin as output
 delay(250);
 digitalWrite (interruptPin, LOW); // sets the digital pin as output
 delay(250);
 digitalWrite (interruptPin, HIGH); // sets the digital pin as output
 delay(250);
 digitalWrite (interruptPin, LOW); // sets the digital pin as output
 delay(250);
 digitalWrite (interruptPin, HIGH); // sets the digital pin as output
 delay(250);
 digitalWrite (interruptPin, LOW); // sets the digital pin as output
 delay(250);
}
void sleepNow(){ 
 set_sleep_mode(SLEEP_MODE_PWR_DOWN); // sleep mode is set here
 sleep_enable(); // enables the sleep bit in the mcucr register so sleep is possible
 attachInterrupt(0, wakeUpNow, LOW); // use interrupt 0 (pin 2) and run function wakeUpNow when pin 2 gets LOW
 digitalWrite(interruptPin, LOW); 
 sleep_mode(); // here the device is actually put to sleep!!
 sleep_disable(); // first thing after waking from sleep: disable sleep...
 detachInterrupt(0); // disables interrupton pin 3 so the wakeUpNow code will not be executed during normal running time.
 delay(250); // wait 2 sec. so humans can notice the interrupt LED to show the interrupt is handled
 digitalWrite (interruptPin, HIGH); // turn off the interrupt LED
}
void wakeUpNow(){ // here the interrupt is handled after wakeup
 //execute code here after wake-up before returning to the loop() function
 // timers and code using timers (serial.print and more...) will not work here.
 digitalWrite(interruptPin, HIGH);
}
void loop(){
 digitalWrite(interruptPin, HIGH);
 //digitalWrite(ledPin, HIGH); // sets the LED on
 counter++;
 delay(5000); // waits for a second
 sleepNow(); // sleep function called here
}

• Filip Franik: Just a thought, shouldn't the detachInterrupt logic be in wakeUpNow method?
• ozkolonur: I don't think so Filip, in most example in internet, you can see, wakeUpNow() is optional to use. most people use it empty function.

Answer 1

I found this, I can confirm it is working. on digispark attiny85.

void sleepTillChg() { // 0.02ma drain while sleeping here
 GIMSK |= _BV(PCIE); // Enable Pin Change Interrupts
 PCMSK |= _BV(PCINT0); // Use PB0 (was PB3) as interrupt pin
 // Turn off unnecessary peripherals
 ADCSRA &= ~_BV(ADEN); // ADC off
 ACSR |= _BV(ACD); // Disable analog comparator
 set_sleep_mode(SLEEP_MODE_PWR_DOWN); // replaces above statement
 sleep_enable(); // Sets the Sleep Enable bit in the MCUCR Register (SE BIT)
 sei(); // Enable interrupts
 sleep_cpu(); // sleep ... Zzzz
 cli(); // Disable interrupts
 PCMSK &= ~_BV(PCINT0); // Turn off PB0 (was PB3) as interrupt pin
 sleep_disable(); // Clear SE bit
 sei(); // Enable interrupts
}
ISR(PCINT0_vect) {
 // This is called when the interrupt occurs, but we don't need to do anything in it
}

credits should go https://www.instructables.com/id/3-Minute-Game-Timer/