MODBUS TCP / PLC Variable Issue

PLCnext Engineer
1

I have just recently started messing around with PLCNEXT Engineer, i am trying to generate a program to read modbus holding registers from a device, (at address 12000 At least just for my test)

I am using PLCNEXT Engineer 2025.02 and my 2152 has firmware version 2024.6.0, so i am using the mobbus tcp library built into the software.

I have been knocking my head against a wall for the last day and i have not been able to find any type of solid information on this online anywhere.
I am trying link my modbus holding register to a PLC variable however no matter what i type in it will not populate on the database and just leaves the value blank, (I do not get any error codes or anything) i have tried every type of data type available while configuring my variables, and it seems no matter what i do i can not tie it into that register.
PC JUST released a MODBUS TCP Video on their youtube channel and in the discussion he more or less glosses over that part. however if i look at his variable type it appears to be a custom data type? however i can not seem to find any information on how to set that up.
(I am very new to this and i clearly do not have much experience when it comes to programming however i am just stuck on this one particular part which is preventing me from moving forward with my project)

Below are some screen shots of the modbus register page as well as where i am trying to link it to a PLC Variable.

image.png

image.png
The type for my Modbus register is an Octetstring(4) , ( I have also tried asking Chatgbt for an example of multiple different custom data types and still i am never able to select a PLC Variable )

image.png
^^ ABOVE is the PLC Variable i am trying to attach to the modbus register.

I am sure this is just my lack of experience and i am missing something obvious however any help would be GREATLY APPRECIATED!!!

Also below is a link to the Youtube video i was using to get this far.
https://www.youtube.com/watch?v=XtWFM3ZmI_s

2

Hi nikkiwiecinski,
it should be connectable to an array of the same size, four bytes in this case.
TYPE
myOwnOCTETSTRING4 : ARRAY[0…3] OF BYTE;
END_TYPE
When I add this custom type to a DataType worksheet
image.pngand create a global variable of that type it allows me to connect it to the register of type Octetstring[4].
image.pngimage.pngNow I can use myVariable within programs etc.

BR
DivisionByZero