Hi TL

You're welcome
Lots of good ideas. ESP32 and wifi sounds like fun but you'd basically have to write an app for it.
Now i never wrote anything for Android but i'm not a fan of Swift/SwiftUI.
I too had lots of plans for playing around but i never actually made the changes. I mean my setting is a bit on the heavy side for parking but other than that i'm actually enjoying the static "weight".

Anyways...
"Is the square wave from 0 to 12V ?"
The MCU is Standard TTL e.g 0 - 5V. The hole idea was to not deal with signal level conversion and just pick it up directly on the MCU.
And this being pretty much standard components anno 1996 that pretty much makes it TTL.

Umeå... Sounds like beautiful landscapes and proper winters.

Best.
/Stig.
A "bit" further down and to the west. And it's not Norway