I'm trying to spec out a project and get a shopping list together and am hoping to get some advice which parts to buy. The Pi will serve as the master and connect to a few arduino's at first, but I'd like to plan for this to scale to the full 32 slave devices at a later date. The idea would be to use the Pi as a common network interface and persistent data storage for the Arduino's without having to fit each individual arduino with their own network and storage modules.
I'm somewhat confused between the MAX485 and MAX13487 modules. Watching some videos it seems to me like the MAX485 modules can only act as either receiver or transceiver, but not both. Is that the case or am I mistaken? Or other differences besides that?
I've also found a few Pi specific RS485 boards(hats) but they all seem to use the Pi's SPI interface to talk to the onboard RS485 chip, which is sort of deterring me from those options because all online guides and secondary reading seem to rely on UART communication. Is this a downside or is SPI more appropriate on the Pi side of the communication? Just seems odd.
The MAX485 modules seem like the most inexpensive option, and if they can in fact do both transmit and receive I'd like to build the whole thing with those. But both the Pi and the Arduino's will need to do both.
Any and all input is appreciated, thanks!