Question

Hi.

I've read this article: https://wiki.teltonika-networks.com/view/RUT955_Monitoring_via_Modbus,
that explains how to read the RUT955 router internal registers with  modbus read  from a Linux terminal.

Is it possible to use the  modbus read  (or another utility) from a Linux terminal to request the router's slave device's registers?

The connection scheme is the following:

• a slave device (PLC) connected to the RUT955 via RS485
• a Linux PC connected to the RUT955 via TCP (a LAN port)

    
 ┌────┐    TCP    ┌─────┐    RS485    ┌─────┐
 │ PC │ <-------> │ RUT │ <---------> │ PLC │
 └────┘           └─────┘    Modbus   └─────┘
    

Answer 1

Hello,

Yes, this is possible, but you will need to use a really limited method for that.

You will need to create a tunnel between your PC and the device that is a master of Modbus. Then SSH into that router and control slaves from that point.

EB.

Comments

As I understand, "the device that is a master of Modbus" is the router in this case.
I can connect via SSH to the router, but cannot get the registers of its slave device.

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No, you can do it. But it will exactly require you to SSH into Master router to reach its slave devices.

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OK. But how do I read the slave devices info when connected to the router via SSH? That's the question.

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In this question thread, there's a command with all the things you can do with it.

https://community.teltonika-networks.com/24215/need-an-example-of-modbus-read-write-request-bash-script-cli

EB.

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Thanks a lot.

Answer 2

Hi.

You can use RUT955 as Modbus Gateway. I did something like that with Python (pymodbus), a RUT955 and Delta PLC.

Comments

I saw there's an option for Modbus Gateway in the Services -> RS485 section.
So this means the router will be an intermediary node between the PLC and the Linux PC?
And the pymodbus should be installed on the Linux side, right?
Thanks.