Modbus/TCP device



I don’t see this topic elsewhere, so I am creating it.

I have a new feeder, OPTO advised me to use Modbus/TCP, so I ordered it that way. Now I want to connect it without spending an inordinate amount of time. I’ve never programmed Modbus or TCP before but I have successfully handled other serial connections. How should I proceed? Is there a worked example that will let me avoid the wasteful frustrating stage of guessing a command, sending it out, and getting nothing back?

I’ve downloaded three technical notes so far but am not seeing a clear path forward.


Opto has a Modbus Integration Kit which is free and will give you all the examples you’ll need. I’m new to the whole Opto world but familiar with Modbus and it worked for me. Here is the link:

Hope this helps.



Hi friend,
To start you must first have an insight on how Modbus works. Specially how the data request is constructed.
Here is a link where you can start
I suggest you first use “Realterm” a free ware application wherein you can experiment on the correct data requests to the Modbus Device.
Please take note that on every Modbus device, you must first know how the manufacturer reads the request and also the response.

Then you can relate the knowledge to Opto22.
I am using Opto22 for 3 months and i am amazed on how many things i can do with it,
Please update us on your progress so I can have additional knowledge,



Modbus Poll might be a little easier to understand as far as programs for poking around/testing modbus. At least for me it is.