[Matthias247]

it actually is, as long as your polling interval is deterministic and meets the requirements of your target application (polling interval < state change interval).

If you look at real hardware (or FPGAs) they will basically do polling: The input gets sampled at each clock cycle and will then get processed. And hardware is definitely realtime :)

The downside of polling is that you burn CPU resources when actually nothing happens. Interrupt driven designs help there.

[sokoloff]

> If you look at real hardware (or FPGAs) they will basically do polling: The input gets sampled at each clock cycle and will then get processed. And hardware is definitely realtime :)

Smiley noted; I think we can agree that "polling at 10s of MHz on an input pin" becomes something quite different than "polling at 10s of kHz on the other side of a USB link".

[jononor]

USB link to a PC with a general-purpose OS likely kills the determinism requirement.