I’m trying to replicate that earbuds functionality that consists in a multifunctional button. If you press this button x amount of times, in a period of time, the earbud will do something depending on how many times you press the button. I don’t know if I’m being understandable (I’m not a native english speaker so it would be nice if you rate my english).

These are my main code and libraries.

#include <mcu_init.h>
#include <millis.h>
#include <button.h>

int main() {

    GPIO_init();

    cli();

    INT0_init();
    TMR0_init();

    sei();

    while (1) {
        
        handleButton();
        
    }

    return 0;

}

#include <millis.h>

static volatile uint32_t miliseconds = 0;

ISR (TIMER0_COMPA_vect) {
    miliseconds++;
    PORTA |= (1 << 1);

}

uint32_t millis() {

    uint32_t time;
    uint8_t oldSREG = SREG;

    cli();

    time = miliseconds;
    SREG = oldSREG;

    return time;

}

#include <button.h>

volatile uint8_t count = 0;
volatile uint32_t lastPressTime = 0;

ISR (INT0_vect) {

    if (millis() - lastPressTime >= 200) {
        count++;
      lastPressTime = millis();

    }

}

void handleButton() {
  
  if (millis() - lastPressTime >= 1500) {
    lastPressTime = millis();

    switch (count) {

      case 2:
        PORTA ^= (1 << 1);
        count = 0;
        break;

      case 3:
        PORTA ^= (1 << 3);
        count = 0;
        break;

      default:
        count = 0;

    }

    }

    return;

}

These are the header files

#ifndef MILLIS_H_
#define MILLIS_H_

#include <avr/interrupt.h>

uint32_t millis();

#endif

#ifndef BUTTON_H_
#define BUTTON_H_

#include <millis.h>

void handleButton();

#endif

Btw, if I call the millis() function before calling the handleButton() function inside the while (1) from my main.c. It starts working. But if I dont do this, neither the timer 0 interrupt works.

I tried everything I could and the only things that worked were:

Declarating miliseconds as an extern volatile uint32_t in millis.h and incrementing this variable by the TIMER0 ISR. I used this variable as my millis().

Calling the millis() function before calling the handleButton() function inside the while (1) from my main.c. In this case, I don’t understand why this is happening and if it’s really necessary to do this call in the main loop.