Implement modbus output

[Justine]

Hi,

I would like to implement a modbus slave on my gateway. The idea is to pass my sensors data on a modbus output, that a software will then access.
I read this topic : http://www.multitech.net/developer/forums/topic/modbus-tcp-with-node-red/ and found out I can’t use node-red to do so.

So the idea, I guess, is to use pyModbusTCP, but is there other ways to do so ? Is there ressources given by multitech or other to do this ?

My other question is how do I access to my modbus : I access my gateway with 192.168.2.1, but how can I poll the slave on 127.0.0.1 ? What are the requierements ?

Does anybody have any ressources that could help me ?

Thank you,
Justine

[Jeff Hatch]

Hello Justine,

I would recommend that you have your pyModbusTCP slave post a listen on the appropriate interface (probably 192.168.2.1 since it sounds from your description that you access the device that way.) You should pick a port to listen on. My recommendation is port 1502 or 502 since that is what some applications use for modbus. You would also need to create a firewall Input Filter rule to allow modbus traffic to the port you pick.

You can package your python modbus application up as a custom application (http://www.multitech.net/developer/software/aep/creating-a-custom-application/) if you want to be able to install the application from Device HQ.

The libmodbus library is also available on the Conduit to build C/C++ applications, but unless you have a good reason to go that route Python is a good way to go for implementation.
Hope that helps.

Jeff

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