Author here. I considered the enum "solution" but found the match on usize tuples to be clearer because it requires less code. Introducing an enum doesn't help because it neither:
+ helps better model the domain: P0 and P1 are already device ports, wrapping doesn't clarify anything,
+ nor does it buy you safety; arguably I'd say it makes it less safe, since the real risk with this sort of code is that you fat finger when copy/pasting between the electrical schematic and the firmware, so by adding extra wrapping you further obscure the pin assignments.
+ helps better model the domain: P0 and P1 are already device ports, wrapping doesn't clarify anything,
+ nor does it buy you safety; arguably I'd say it makes it less safe, since the real risk with this sort of code is that you fat finger when copy/pasting between the electrical schematic and the firmware, so by adding extra wrapping you further obscure the pin assignments.