Re: [milo-dev] Configurable OPC-UA server based on Milo

[Kent Randall <point85.llc@xxxxxxxxx>]

Hello Stefano,

The idea of looking at open62541 was to see if you can find a C device driver.  If so, you can always use the Java Native Interface (JNI) to communicate with it.  By the way, if you are interested in how I am using a Milo client, please take a look at my Overall Equipment Effectiveness (OEE) project at https://github.com/point85/OEE-Designer.

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On Mon, Feb 11, 2019 at 6:58 AM Kevin Herron <kevinherron@xxxxxxxxx> wrote:

> Is it correct to attach an attribute delegate to that node so the adapter is notified of writing operations and then send back that value to the machine?

That's one way to achieve this, but AttributeDelegates are not really meant to be used when the attribute read or write might block, and if you're talking to a machine that's definitely the case.

What works best is to handle this in the write() method of your Namespace. In a real world implementation you can split the incoming writes into writes that can be done quickly (in memory, directly against a Node possibly via its AttributeDelegate), and those that need to be handed off to other system to complete. All the methods on Namespace are non-blocking/async so your implementation has a chance to do something smart like use non-blocking IO to communicate with external devices, if possible.

On Mon, Feb 11, 2019 at 6:31 AM Stefano Lissa <satollo@xxxxxxxxx> wrote:

Thank you Kent, I'll look at that C++ project even if I'm a long time
(and a bit old) Java coder so I feel myself more comfortable with
Java.

Just a question (and please let me know if those kind of discussions
should be moved on another forum/mailing list): I'm playing with Milo
and I wrote an adapter which is able (actually not, but...) to
communicate to a with a custom machine and that adapter setup a node
to expose a specific machine value. Is it correct to attach an
attribute delegate to that node so the adapter is notified of writing
operations and then send back that value to the machine?

Thank you, Stefano.

--
ing. Stefano Lissa
LinkedIn
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