Re: Simple Components 4.12 with MQTT implementation released

[slos <new.stephane.los@gmail.com>]

Le vendredi 15 avril 2016 10:01:31 UTC+2, Dmitry A. Kazakov a écrit :
> On 14/04/2016 23:30, slos wrote:
> 
> > Be prepared to ear about it soon.
> > Just google for "industry 4.0 opc ua"
> 
> Well, actually I am involved in an Industry 4.0 project:
> 
>     http://www.secureplugandwork.de/servlet/is/10291/
> 
Good to know !
Thank you for the link.

> We indeed use OPC UA in this project. But OPC UA is unsuitable for field 
> automation, basically, for any work associated with data acquisition and 
> control.
Of course but like nobody, I don't intend to use it in this case.
There are already plenty of industrial protocols fitting here.
"Ada for Automation" is using libmodbus for Modbus RTU and TCP communications and Hilscher boards for all major field buses.

> Therefore the architecture is that the OPC UA is only a gateway 
> to the applications. All actual the work is done by the middleware 
> developed by cbb software GmbH running on the system nodes (ARM boards). 
> The middleware feeds an UPC UA server which the gateway's OPC UA client 
> accesses. BTW, the middleware is 100% Ada and 0% OPC.
We share some of the vision.
"Ada for Automation" is a framework with which one can build his own control application using Ada. I would not call it a middleware.
And MQTT or OPC UA would just connect it to some SCADA or cloud based application like one using IBM BlueMix.

> Note that without OPC UA everything could work far better and require 
> far less resources. E.g. having all process data the OPC cannot access 
> because it is too slow to pace with the middleware capable to deliver 
> data at less than 1ms rate and does not properly support 
> push-subscriptions, does not support distributed time stamping, physical 
> units, error states etc.
> 
I agree that OPC UA does not fit where EtherCAT, Sercos III or PROFINET IRT would.
OPC was created for office and SCADA / GUI applications access to PLC data, not for IO processing.

> That was the reason why it was decided that the OPC UA gateway would not 
> deal with process data at all. It is used only for configuration and 
> possibly for history process data.
> 
> In short, there are serious multiple reasons why OPC UA cannot be used 
> in the field, regardless how strong the push for it is.
> 
> -- 
> Regards,
> Dmitry A. Kazakov
> http://www.dmitry-kazakov.de

Stéphane