attachInterrupt an einem Pin

The attachInterrupt function tells your board: watch this pin, and the moment its signal changes, run my function right away.

Not every pin supports interrupts. On an Uno only pins 2 and 3 do, so plug your signal into one of those.

Wrap the pin in digitalPinToInterrupt so the right interrupt number is used. It keeps your code portable across boards.

You give attachInterrupt three things: which pin to watch, the function to run, and the kind of change that should trigger it.

The function you name is your handler, also called an ISR. The board calls it automatically; you never call it yourself.

Pass RISING to fire when the pin goes from LOW to HIGH, like the moment a signal first switches on. 📈

Pass FALLING to fire when the pin drops from HIGH to LOW. A pull-up button often triggers here, since pressing pulls the pin down.

Pass CHANGE to fire on either edge, both up and down. It is handy when you care about every transition of the signal.

Call attachInterrupt once inside setup, right after you set the pin mode. From then on the watching happens on its own.

With the interrupt attached, your loop no longer polls that pin. The handler runs only when the chosen edge actually occurs.

If you ever need to stop watching, detachInterrupt removes the link. Most projects attach once and never detach.

Which trigger mode fires only when a pin goes from LOW up to HIGH?

You learned to call attachInterrupt with a pin, a handler, and a mode like RISING. Now hardware runs your code the instant a signal changes. 🎉