test if SCXI chassis is on

[hrobitaille]

Is there a way, from LabVIEW RT, to determine if the SCXI chassis is connected and powered or if a SCXI module is plugged or not ?
I was surprised that I didn't receive error if I ran my acquisition program (using virtual channel) when my SCXI chassis was powered off.

[Filipe A.]

Hello;

This is actually a design feature. It is similar to being able to read an analog input channel on a data acquisition board even if it is not wired to anything. Developers call it "simulation mode". There is a way to test whether or not the chassis is powered on before accessing it from software. In NI-DAQ 5.0, there is a function called SCXI_ModuleID_Read. Given the chassis ID and slot, it will return the module ID. If the chassis is turned off, it will return a 0. If the cable is not connected to the chassis, then the pins float high, and it returns a -1. Other problems with the chassis setup (wrong adapter, bad jumper settings, etc.) might cause a 0 or -1 to be returned, but if you have already tested the chassis and modules, and know that everything is set
up correctly, this is a good way to programmatically check to see if the chassis is turned on.
I believe that in Labview, you can use the Get SCXI Information.VI for the same purpose.

Hope this helps.
Filipe A.
National Instruments

[hrobitaille]

Thanks for the information.
I have found an example on the Web site : SCXI ModuleID Read.VI which call the SCXI_ModuleID_Read function. I have added a check of the returned status before to use the module ID information because, at least with the last version of NI.DAQ, this information is valid only if the chassis is connected. In the other case, the returned information is the same than the previous call instead of -1.

Regards
Hubert