Event Based Publish Messages with HP SDK PubSub

[joergS]

Hello,
I am using your HP SDK with the PubSub extension.
Currently I am trying to create an application where different devices exchange data with each other. This is a network of several devices, not a classic client-server relationship. Therefore, my approach is to realize the communication via OPC UA PubSub.
Some of the values that I want to transfer are changed after certain trigger events. The server then also fires an event for these.
Since events can also be published via PubSub, it seems to me to make sense to publish the event via pubsub and not the corresponding variable value from the address space.
In the source of the HPSDK I also find some pieces of code that look to me like events are published there. However, I cannot find an example of how I can configure such an event-based data set. I have tried using the UA Expert. But I can't find a way to get an event into a DataSet Writer.
Could you please give me a hint or an example for event based published data sets for the HP SDK, and how they are configured.
Thanks.
Joerg

[Support Team]

Hi,

in the current version of the PubSub protocol stack, event frames are not supported, neither on the DataSetWriter nor on the DataSetReader side. The current version is released for "cyclic data communication" only. Integrating the event frames is an option when market demand is raising. As for now the original Client/Server relation adds advantage for events (and specially to alarms) when it comes to acknowledgement and auditing.

[joergS]

Thank you for your reply.

So I will try to realize my application with the cyclic data communication.
Here it would be helpful for me if the data is not published with every cycle interval, but only when the respective value has changed.
Is it possible to configure the publisher so that data is only published when it changes? If so, I would appreciate a hint or an example.

Thank you!

[Support Team]

Hi,

the "notification on value change" is the default communication pattern in the Client/Server type cmmunication as of OPC UA.

Within the PubSub communication pattern we do not support the "DeltaFrame", that allows for sending changes (the delta) only. We just support the "cyclic", because that is the main use case for the "field type" communication as of OPC UA FX.