That's... not very well designed, what with the near-zero clearance/creepage distance.
Good point. I like the gas discharge tube though. And the send/receive LEDs - though I'd likely remove these when finalised, to save a couple of mA... Do you know of a better/cheaper option? Not sure I want to design a board for this
as well, especially considering it's taken me weeks to (not) design the RTU
On CAN bus: Certainly an option. Probably not a much better option though; it's a better protocol for a multi-master system (not entirely relevant here), but also much more complicated.
All I know about CAN Bus is that it is "multi master", and that people keep saying it's complicated
Multi master is nice I guess, since it would allow the RTUs to push notifications, but I don't like "complicated".
My thinking was that the built in controller on e.g. the ATMEGA16M1 would save me at least the step of implementing the communications controller firmware, leaving me free to concentrate on the PWM/control side. I haven't seen any, but maybe there are MCUs with built in Modbus support?
You'll still need transceiver chips, but at least it seems like they have lower quiescent current.
Low power consumption is high on my priority list.