work in progress ---
Getting Started with Utgard - a tutorial
What is Utgard?
If you found out about Utgard, then you probably know what it is for. But for the uninitiated here a short introduction:
OPC (http://en.wikipedia.org/wiki/OLE_for_process_control) is a industry standard to allow a unified access to a varied number of devices, be it controller of any kind, sensors, whatever. Many specialized hardware components have their own OPC Server (e.g. WinCC, ABB, ...), but there are quite a few implementors which provide generic "OPC servers" which provide access to devices via a wealth of protocols. Prominent examples are Matrikon (http://www.matrikonopc.de/opc-server/) or Software Toolbox's TOP Server (http://www.toolboxopc.com/index.html).
Utgard only supports the client part of the OPC DA 2.0 interface, so any OPC UA setup (which is increasingly popular) will not work!
For the purpose of this tutorial, we will demonstrate the usage with TOP Server, but any other OPC server should work.
Setting up TOP Server
The installation of TOP Server is pretty straight forward, no surprises there. The tricky part is actually the DCOM configuration. Helpfully on the TOP Server website is a comprehensive guide (http://www.opcactivex.com/Support/Tutorials/DCOM_Tutorial_-_Configuring_th/dcom_tutorial_-_configuring_th.html), which explains how to configure it. If you do all the steps, the DCOM configuration should work. At least it did in our test setups. If it doesn't contact your local system administrator or OPC Guru to help you out. Problems may arise from a large number of causes (firewalls, routers, permissions, ...).
The important bit is, please try to access the server from a different computer to ensure the communication really is via DCOM and not through a local COM call. For this you can use a OPC Client, here we used the Matrikon OPC Explorer.
Even though no additional items are configured, you should be able to access the TOP Server internal items, like shown in the screenshot. It can be tricky to setup the security, for this example I had to create the identical user on the client machine and then to start the OPC Explorer with this user, to access the server at all.
This is already enough to get started with the first step, getting updates from one of the existing items.
Retrieving values
As we could see in the section above, there are already some items available, we want to use one, that is permanently updated, so in our example we will use the tag "_System._Time_Second"
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Until then have a look at this great post: http://clifcarr.blogspot.de/2011/02/readwrite-to-opc-serverplc-register.html