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Topic starter
Hi
A customer uses BACnet and COV method to refresh data.
Problem : at start up some data which don't change much are not refresh right away but after a while.
Is there an option to force the refresh of COV value at start up?
Francois
Posted : 29/05/2013 11:57 pm
Hi Francois,
When PcVue subscribes the data as COV the device should sends back the current value.
In your case, it probably doesn't do it and send the value when the data change.
The issue is on the device side. There is nothing to do except improving our driver by sending a read request after subscription.
To prove your issue is this one you must create an empty project, configure the Network + device and map 1 variable as COV.
When you click Apply on the Variables creation dialog you will see in Wireshark the subscription request sent to the device. If you don't see any instant notification with the actual value then you can conclude this is the issue.
Posted : 30/05/2013 7:42 am
Hello!
Same issue encountered.
I want to add just one thing:
Any BACnet device have a maximum limit for tags in COV subscription and is never declared on the PICS! :angry: :angry: :angry: :angry:
So is it possible that if you make a test with an empty project & 1 COV tag, it will work good! :S
Posted : 30/05/2013 1:34 pm
Yes Filippo that's right. The COV limit is given the Device Object.
But if you reach the limit you won't have the same effect than the one described by Francois.
Actually you will have an error on the subscription.
Posted : 30/05/2013 2:33 pm
Topic starter
Thx guys for your answers.
There's a lot of equipment (>100) and the SI doesn't have access to it (they're managed by the end user and are wild located)
I also talked with Jerome, and he suggests to rise the number of "COV maximum concurants transactions" in the advanced option sof the BDS admin, to optimize the subscriptions at start which could help with lots of equipment.
The SI is going to test and see
Otherwize, we may have to develop something to first poll and then switch to COV
I'll let you know
François
Posted : 30/05/2013 10:20 pm
Hi François,
Is it possible to know the manufacturer of the plc ?
Actually, you can see with wireshark the subscription request and just after that the notification.
Do you have wireshark logs ? So if you don't see that probably there is a problem but from the device.
For the limit of subscription you can see that in the web server of the device (I see that with TREND devices).
Posted : 10/06/2013 7:23 pm
Topic starter
Hello Brice,
Thank you for your info
Actually the SI don't have the pics for the devices because the devices are managed by another departement and we even don't know what devices it is...
We get the Wireshark traces and it seems that some devices are not COV compliant but there's no subscription on, so the problem may be from somewhere eles.
Jerome is analyzing that and askedfor another test with BACnet traces in PcVue to check
FYI all details are in the ticket#86646,
Posted : 11/06/2013 5:51 pm