I guess improvements are never ending, but I'll wait to receive the v.02 boards and test them before I send v.03 off to the fab.
I noticed a few things I should improve in the next version of the board:
- Use two pairs for the RJ45 power, instead of one pair. I'm thinking of adding pins 4-5 for the extra power pair, but i'll make 4-5 VIN and 7-8 GND, similar to PoE.
- Change the 2-pin jumper to 2-position DIP switch. That will make it possible to connect RE and DE to GND (they're pulled up by default) by switching the sliders to ON, which means less wiring from the JST connectors to devices.
- Add a 3-pin header to tie RJ45 power pins to VIN. This way each board can be powered independently if needed (jumper off).
- Add a Schottky diode to prevent reverse current.
- Use a different 5V switching voltage regulator, and use electrolytic capacitors for its input/output bypass filtering (in addition to ceramic). These will prevent issues of fast high switch-on DC voltage (can easily ramp up past 36V) and will still enable proper noise filtering.
These are minor improvements, but they'll slightly increase safety and make usage/deployment a bit simpler.
I'm still on the fence regarding the 3-pin header for tying RJ45 to VIN. If there power coming into the board while the jumper is removed (or added), it could be quite dangerous to touch. I'm not exactly sure how to work around that.. I don't like the idea of exposing VIN on a 2.54mm pin header..