lagger 
As per topic, i'm pondering how to do this in the best way.
Each PCB is supplied in a star topology from a single point, but each also needs a separate logic supply.
Should I use a bus vertically with repeaters for each row. Or is it enough to just serpentine it with logic power across all 30?
The PCBs are 16cm by 16cm, so the serpentined bus would be just over 6m.
Your subject line talks about RS485 but your message seems to talk about power. I am confused. I also do not understand
Each PCB is supplied in a star topology from a single point, but each also needs a separate logic supply.
Jim
js 
RS485 and star topology don't mix too well either. May work at low speeds and 6m of cable.
Agree on RS485 and star, if that is what was described.
It will REALLY depend on baud rate. At lower baud rates, you can still get transmission line reflections but they have less impact on the waveform of the data. It samples, after all, at three sample points near the middle of each bit. It ends up looking more like capacitive loading with a bunch of short star branches.
So, a critical question is: what is the needed baud rate?
Jim
lagger Fair enough, disregard the stuff about power.
I never intended the rs485 to be a star topology. It was more a question of having a bus vertically with a repeaters for each row, versus having a single cable with plugs for every 20cm that connect to every pcb (which would put the number of devices on the bus to 31+).
Because if repeaters are necessary, I'd have to figure out how to make them.
A baud rate of 57600 or 115200 would be fine.
