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



  • 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 ????


  • administrators

    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



  • 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.

    0_1554973450320_37991de2-5c44-4dbc-890c-a3bd227f9d24-image.png
    when i set mode operation to RUN and switch on qModMaster for Modbus, i always get timeout error.
    0_1554974332879_mosbus master.png
    Am a little bit confused about hostlink protocol OR modbus ...


  • administrators

    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