Node-RED will be used on the Raspberry Pi 4 to communicate serial Modbus RTU to a Solo process temperature controller and Click PLC using twisted pair RS485. This will be done on the same serial network so the devices will be daisy-chained together on the two wires.
We will be reading the PV (present value) and SV (set value) of the Solo temperature controller and then writing these values into the Click PLC. An SV value will then be read from the Click PLC and if it has changed, the value will be written to the SV of the Solo controller. Let’s get started.