Read data sent from Omron Plc by serial port using Node-Red

[Methlouthi Hathemi]

i have set a variable on Omron memory to DM200 address, and i want to read this variable on node red.
i have put all the necessary configuration (parity, baude rate, .. ) in serial node and modbus-Read node but i have nothing received on msg debug node.
So, i wonder if i set variable address wich is DM200 ,in my case, to be able to receive data on node-red ????

[Martin Kudláček]

Hello @methlouthi-hathemi,
although your question is not about the UniPi PLC, I'll try to help you

1. Validate, that your serial port is working in your PC (available as a COM port on Windows or /dev/... device in GNU/Linux)
2. Understand what type of software communication protocol is on the serial port (ModbusRTU most probably)
3. Test basic communication with some dedicated software (e.g. qModMaster for Modbus)
4. Replicate the settings in Node-RED: name of the serial port, speed, parity, stop bits and so on
5. Use appropriate node in Node-RED for your communication (https://www.npmjs.com/package/node-red-contrib-modbus for Modbus)

Best regards,
Martin Kudlacek

[Methlouthi Hathemi]

Hi @Martin-Kudláček first, thanks for ur reply. Am trying to read data from Omron CQM1. Here's a screenshot of the configuration in CX-programmer.

when i set mode operation to RUN and switch on qModMaster for Modbus, i always get timeout error.

Am a little bit confused about hostlink protocol OR modbus ...

[Martin Kudláček]

Hi @methlouthi-hathemi,
first of all, are you sure you have the correct cable? The cable has to be crossed, not null modem.

Second of all - are you sure you have some register number 0? It is common that the number and the address of registers are mismatched (numbers of the registers should go from 1, addresses should go from 0).

Best regards,
Martin