Pin Change Interrupts debounce

[mfalkvidd]

@alexsh1 how about adding global variables for all interrups like this

volatile unsigned long lastInterruptD1 = 0;
volatile unsigned long lastInterruptD2 = 0;
...

and inside the ISRs set the corresponding variable to millis() like this

lastInterruptD1 = millis();

and in loop have a series of

if(lastInterruptD1 != 0 && millis()-lastInterruptD1 > DEBOUNCE_MS){
  lastInterruptD1 = 0;
  // Do whatever the interrupt does here
}

You could use an array instead of individual variables to make the code cleaner, especially if you want to cover a lot of pins. Which board/Arduino are you using?

[alexsh1]

@mfalkvidd it is a custom made board using atmega328p-au with sensebender bootloader running at 8Mhz and 3.3V.
I'll try the above, however, does millis() work while sleeping?

[mfalkvidd]

@alexsh1 it will return the last value, but it will not increment. That's one of the reasons ISRs should exit quickly.

[alexsh1]

@mfalkvidd
Want to share what I found in case others have a similar issue.

const unsigned long debounceTime = 50;
volatile bool ir_selector_pressed = false;

ISR (PCINT2_vect) { // handle pin change interrupt for D0 to D7 here
  static unsigned long previousStateChangeMillis = 0;
  static bool previousPinState = HIGH;

  bool pinState = digitalRead(SELECTOR_BTN);
  if (pinState != previousPinState) { // ignore pin changes of pins other than SELECTOR_BTN
    if (pinState == LOW) { // only falling events
      if ((millis() - previousStateChangeMillis) > debounceTime) { // debounce
        ir_selector_pressed = true;
      }
    }
    previousPinState = pinState;
    previousStateChangeMillis = millis();
  }
}```

[alexsh1]

Another way to debounce is to stop interrupts in loop, sleep for say 20 seconds and then resume interrupts.

[Yveaux]

@alexsh1 this is in general a bad idea, as it will also stop eg reception of serial data and incoming packages (when using message queuing).

[alexsh1]

@yveaux you mean stopping interrupts?

[Yveaux]

@alexsh1 yup

[alexsh1]

@yveaux What is the best way to do it please?

[Yveaux]

@alexsh1 The easiest way would probably use a debounce-library.
These normally aren't using interrupts, but you have to question yourself if you really need interrupts in your case.

I don't have any readymade, tested code which uses interrupts and debounces switches.

[alexsh1]

@yveaux said in Pin Change Interrupts debounce:

@alexsh1 The easiest way would probably use a debounce-library.

I'll look into that. Thank you