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July 1, 2022 - I have a RUT955 can cannot get the MODBUS-RTU Serial polling my PLC. I am just trying to poll for two registers to start with before I add any more. I am not able to get technical support in the USA, so I thought I would try this forum. There is a small LED that is flashing red/green on the back lower right near the LTE signal strength bars. Not sure if that means polling.

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Be advised, that the RUT955 is fully supported by official openwrt. Based on this, Being a freelancer, I developed custom firmware for a large fleet of RUTs to be used as data  concentrators in IoT. Lower level devices are connected via ModBus/RTU, no problem. In your case, you should try to connect a ModBus Simulator, i.e. ModRSsim2, to your RUT, to verify the polling, and electrical setup.
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Thank you for contacting Teltonika networks Crowd support.

From the pdf file shared I can note that you are using an old firmware on RUT955. Kindly update to the latest firmware for this solution is based on RUT9_R_00.07.02.3. To update the firmware, go to

SYSTEM >>FIRMWARE >> UPDATE FIRMWARE you can update from the server (Recommended) or download the firmware from https://wiki.teltonika-networks.com/view/RUT955_Firmware_Downloads

And update from file.

The following links shows step by step on how to configure Modbus and RS232.

For testing purposes you can use a Modbus Simulator of your choice like ModRsim2.



Kindly follow the above steps, for more technical support, revert.

Kind regards,