Hi,
thanks for the traces!
It looks like, that the Arduino slave device is using the Unit Identifier 1, but the PLC queries the Unit Identifier 0.
Unit Identifiers are “Modbus device addresses” (they were used in serial based networks like RS422/RS485 to communicate to more then one slave).
I’m not sure if the Arduino slave cares about the Unit Identifier, but maybe it wants to get the right one?
So please set the Unit Identifier in your ModbusTCP_any configuration to 1, and try if something changes.
