I imagine that the proper way to implement an RS485 multidrop bus is the following:

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What happens if, in order to save cables, I connect the same 5 nodes above using this other topology?

enter image description here

  • Will it works?
  • If no, why?
  • If "maybe", under which circumstances will it work?

P.S.: yes! I know that MEGA has three Serials and, as such, I could implement two different BUSses (1: Mega<->Mega<->Mega; 2: Mega<->Nano<->Nano), but this will increase the complexity of the software I'm running, as it needs some hacking in order to play nicely with two distinct RS-485 busses;

P.P.S.: This is the bus discussed in this other question

1 Answer 1


At low speeds and short distances that won't be a problem.

At high speeds (megabits per second) and long distances (hundreds of meters) you may get reflections unless you get the termination just right.

  • Can you please tell values you think is reasonable to call "short distance" and "low speed" in this context?
    – Largato
    Jun 2, 2022 at 1:59
  • 1
    @Bacco tens of meters and 115200 baud, I'd call short distance and low speed.
    – Majenko
    Jun 2, 2022 at 12:06
  • Thanks for your feedback!
    – Largato
    Jun 2, 2022 at 16:25

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