Final revision no really!
I think the number of times I've said "this is really the final revision" is now too numerous to count, but honestly this time I think it's fairly close to final. (That's downgraded from yesterday's remark to people that asked, where I said "actually is final".)
The most recent scare with the design was what looked like a short in the antenna cable causing various things to reset and may now be damaged. It's unclear to me exactly what happened, but we're no longer getting a stable consistent GPS lock. The antenna is active - it has 3.3V fed up into it to power an LNA in the weather-sealed puck antenna - but there's no current limitation on what's fed up this path.
The datasheet for the GPS has a large example circuit to provide hints to the GPS chip that either the antenna is disconnected (only works for active antennas), or has a short and automatically disables the power into the antenna. But the design is far more than I really need, and takes up enough board space I'd have to do some serious rearrangement. It'd be nice to use the GPS chip's LNA control line and reporting antenna modes, but the main thing is just limit current and suppress shorts.
I've generally ignored putting any significant additional current limitation into the design because none of it is exposed to any external connections. All the failure modes of any of the parts would just result in the board being tossed rather than fixed, and none of them actually are subject to external connectors - except now realising the antenna is directly. (The ethernet jack does have power going into the internal side of the transformer, but since it's internal side a broken cable plugged into the jack doesn't cause more power to be drawn.)
Instead, I've decided to just add a simple PTC fuse to the power input side of the antenna, limiting it to 125mA which is comfortably more than any active antenna should need, but should blow fast enough to prevent significant damage to the board. Whether I add some remote control of that power using a MOSFET or some sort of reporting of the failure to the GPS or MCU I haven't decided. It depends on how much board space I need. A PTC fuse is small enough to just throw one on there without much concern.
(PTC fuses are tiny resistors which have a Positive Temperature Coefficient, that is as they try to carry more current they heat up, and a high enough current/temp will result in a very high resistance, enough to stop the current flowing. They reset themselves by cooling down. Their self-resetting nature and simplicity makes them useful for this sort of case. PTC fuses are commonly used in external power ports such as USB.)
Hopefully, that'll reduce the risk of a short! Soon it will be ready!