Browsing Logix Tag Names Through External App

Python Dev/AB PLC programmer here,

So I'm writing a python app that does some interfacing with a ControlLogix or CompactLogix controller. I understand that A tag is simply a shortcut to a specific EtherNet/IP CIP Object Instance and Attribute within the controller and knowing the tagname I can read and write to it through an "unconnected message". How can a guy get the tag names out of the controller? Oh yea, by the way, I don't want my user to have to install studio5000 or RSlinx(OPC server) is there any other way to get the tag names through an ethernet connection that anyone knows?

inb4: why would I want to do this?
I want to do this so my app can auto complete tagnames for my user when they specify which ones to read or write to.

Welcome to the PLCTalk forum community !

Reading the tag database and all of its structures is a nontrivial task even if you already have a solid CIP driver under the hood.

Start with the Logix 5000 Data Access Programming Manual:

http://literature.rockwellautomation.com/idc/groups/literature/documents/pm/1756-pm020_-en-p.pdf

The Get_Instance_Attribute_List service in conjunction with the Symbol object are, I think, what you want to look at to browse or query the controller's tag database.

It gets hairy in a hurry if you want to allow your client access to every data type and every subelement of every structure.

Take a look that this thread:

http://www.plctalk.net/qanda/showthread.php?p=700740

So pylogix (what Jordan was pointing to) can get the tag names from the controller, which may help you to an extent. It will retrieve the controller and program scoped tags. It does have a limitation though, it won't interrogate user defined tags. I've experimented with UDT's, just haven't worked out anything solid.

Hello,

If you want a free program you can use to WireShark for information, read here: http://www.plctalk.net/qanda/showthread.php?t=113081

Wow, Great responses guys! I'll be working for a bit to understand all of these suggestions, but I intend to check into all of them thoroughly.
Thanks alot!

Hello, I am trying to do something similar to JDuzan, but in C++. So, I am trying to implement the access scheme described in Rockwell's "Logix 5000 Controllers Data Access" document. Most of what I've read makes sense, but I haven't figured out how to get the array size of an atomic symbol.


I can see how the array size is determined for struct symbols using the Read Template Service, but I don't see how to get the array size for a symbol that is an array of atomic elements. The Symbol Type obtained via the Get Instance Attribute List service gives the number of array dimensions, but not the size of each dimension.


Have I not understood the Rockwell document correctly? I see that DMRoeder's excellent pylogix software adds an extra attribute (#8) to the Get Instance Attribute List service request, which does seem to get the array size information. However, I haven't found any documentation that covers attribute 8 of the Symbol class.