Showing results for 
Search instead for 
Did you mean: 

Connection between Siemens HMI and ctrlX Core via OPC UA

Connection between Siemens HMI and ctrlX Core via OPC UA

Established Member

Hello Comunnity,

here is an onfield commissioning issue about the connection between a Siemens HMI (client) with our ctrlX Core (server) via OPC UA.

For engineering we are using 1.12 version for ctrlX Core Apps and ctrlX Works, while using TIA V16 and WinCC RT Professional V16.0.0 for Siemens component. 

In short word, the OPC UA connection was built up successfully but the variables in HMI were not working properly. 

For details plz. refer to the attached slides. Also the OPC UA certificate from Siemens is attched. 

We have tried several combinations of configuration in the client but none were useful. Please help us to find out the solution.

Thanks and best regards,



Community Moderator
Community Moderator

Hello Hui

I personal have no experience with TIA portal. Maybe any other community member will post his know-how...

Until this maybe it will be a good idea, that you try another OPC-UA client (e.g. UA expert) to see if you can read this values from the ctrlX. So you see where the problem is located...



Hello Joachen,

Later we have also tested with UA TestClient, WinStudio V14 Client and WinStudio V15 Client to connect with our ctrlX Core Server. 

The result was that:

ctrlX UA TestCleint and WinStudio V15 -> successful (IsCA: true)

Siemens WinCC V16 and WinStudio V14 -> failed (IsCA: false)

Besides we have found out in the certificate detail that there is a line "IsCA", which is correlated with result. And we estimate that this might be the reason for the failed OPC UA connection. 

So could you please help contact our R&D to explain what does IsCA mean?  And how can we fix it?



Hello Hui,


I'm not sure if this is really a certificate issue. Because as i saw in your slides you are already connected. The address space of the server is shown (slide 7).


To have a more detailed diagnostic it would be helpful to see a log/ trace of the Siemens client. Is this possible?

Also there are may some Rexroth server logs inside the Diagnostic Logbook. Have you checked this?




Established Member

Hi Hui,

I suppose that the certificate can be the issue. But probably because of the wrong SHA algorithm. Did you already try out the newest Version 1.16 of our Server App? There we provide a SHA256 and SHA1 key to solve this problem. Probably this also helps you.

The "isCa" is not relevant in this case and will ignored by our Server.

Best regards,


Any news and/or can this topic be closed?