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Gateway channel caching ?

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Configuration : VeriStand 2011 SP1


I'm working on a .NET application that collects channel values by using VeriStand Gateway. The data collection is cyclic with a period that can be changed by the operator. On my system (PC running .NET app + Gateway connected to a PXI RT target) it seems that when the scanning period si set to 15 ms, the Gateways returns me 4 times the same value (i.e. watching the "System Time" channel).


It's not an issue for me, because my custommer only requires a maximum scan frequency of 20 Hz. But I have to explain the limitations of the "GetMultipleChannelValues" method (is there some caching mechanisms or somthing like that ?). Anyway can I assume that the Gateway delivers a data not older than 40 ms ?


Thanks for the clarifications, best regards.

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Message 1 of 4
Accepted by topic author thumble
By default the target will send the latest channel data to the gateway 15 times a second, which is around a 60ms period. This is the data that the gateway returns when you call GetMultpileChannelValues. This is done to save CPU usage on the target and network bandwidth.

You can configure a target to send data more often than 15Hz, but you have to edit the system definition manually to do so.
Jarrod S.
National Instruments
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Message 2 of 4

Ok, your reponse is very satisfactory. It may be interesting do clarify what to edit in vssdf to change the period if someone needs that.



Message 3 of 4

You can use the System Definition API to set the rate at which targets send data to the VeriStand Gateway using the DataRate property for the target. The default is 15 Hz, but you can change that. See the attached example.



Jarrod S.
National Instruments
Message 4 of 4