TCP/IP or RS485 for your Arduino home automation
7At a juncture in your home automation progression, a pivotal decision arises concerning the choice between TCP/IP and classic serial for your Modbus implementation. Personally, I find pragmatic advantages in the latter option. It requires fewer installed devices, ensures a consistently available network by employing a single wire for all connections, and the RS485 shield for Arduino presents more versatile mounting options for sensors, with numerous ground and power pins, offering a more flexible configuration options. However, it is crucial to acknowledge the flip side—the Ethernet shield appears to exhibit instability for continuous 24/7 operations, at least based on my testing.
The link for a basic Arduino Modbus "network" using only two UNOs and two RS485 shields (can be replaced with SoftwareSerial easily) can be found here:
https://gebsystems.com/a-shift-from-arduinomodbus/