Well the Node-RED software we provide consists of a set of preinstalled nodes that others have written in the community.
Each node usually has a hosted web site that explains how to use it. The same applies for the Modbus nodes like this web page shows:
https://flows.nodered.org/node/node-red-contrib-modbus. Here all the details are explained.
Please read this thread
https://forum.hilscher.com/Thread-NPIX-R...-available that tells you to activate the RS-485 driver to run in auto-direction control. There is a also a very simple Node-RED flow that you can copy and insert in your Node-RED.
Here a very simple code to use Modbus RTU as master/client to read out a Modbus register from a server (Mitsubishi) with Modbus address (Unit Id) of 1 at a baudrate of 9600,7,1N.
Code:
[{"id":"38958c5.2fe5974","type":"modbus-read","z":"4411c241.bb70ac","name":"MyRead","topic":"","showStatusActivities":false,"showErrors":false,"unitid":"1","dataType":"HoldingRegister","adr":"0","quantity":"2","rate":"100","rateUnit":"ms","delayOnStart":false,"startDelayTime":"","server":"d0f81b82.fb6ad8","useIOFile":false,"ioFile":"","useIOForPayload":false,"x":610,"y":260,"wires":[["6745989e.9bd2f"],["6745989e.9bd2f"]]},{"id":"6745989e.9bd2f","type":"debug","z":"4411c241.bb70ac","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"false","x":860,"y":260,"wires":[]},{"id":"d0f81b82.fb6ad8","type":"modbus-client","z":"","name":"MyRTUTest","clienttype":"serial","bufferCommands":true,"stateLogEnabled":false,"tcpHost":"127.0.0.1","tcpPort":"502","tcpType":"DEFAULT","serialPort":"/dev/ttyS0","serialType":"RTU-BUFFERD","serialBaudrate":"9600","serialDatabits":"7","serialStopbits":"1","serialParity":"none","serialConnectionDelay":"100","unit_id":"1","commandDelay":"1","clientTimeout":"1000","reconnectTimeout":"2000"}]
And yes I agree that usually the PLC should be configured to be of type "slave/server" but you need to verify it if this is true.