Modbus TCP Master

[Chris_Sobo]

Hi,
we work with alot of teltonika Rut955 and Rut956 with the modbus gateway function to communicate with heating controllers.
This works absolutly fine.

What i am trying to do now is to write a register periodically to a certain value. Therefor i wanted to use the Modbus TCP Master function. But i have a strange behavior.
On one Router the Command executes as expected, on the other the Modbus command turns into complete rubbish.
Please have a look:

on the second image you see that the response has something like function code 131 in it.
On both Router itś the same modbus device with the same communication settings.

Do you have an idea, what’s the problem?

[Martynas]

Hello,

For writing data into a register, you should select Function – Set Single Holding Register (6) instead of reading:

Let me know if you need any further assistance.

Best regards,

[Chris_Sobo]

I´m aware that I need to write with a different function code. The problem is, that even reading isn´t working properly, so that i won´t write, unless the router is reading and later writing the correct register.

So, to be clear, the problem is, that the router is reading not what i want to read.