8 second delay when starting two PCI4472 with RTSI cable

[TroyR]

Hello,

I have two PCI4472 cards that are connected with an RTSI. I am using LabVIEW 8.2 and DAQmx to communicate with the boards. Everything appears to be working, however, on the start of the DAQ operation there is a ~8 second delay before data arrives. When I run the same code with a single 4472 there in no delay.

Is this normal operation?

Thanks in advance,

Troy Richards

[Jeff_T.]

Hi Troy,

I would not consider this expected behavior, please tell me more about the problem.  Is the data that you are receiving correct?  If it is correct this sounds like the delay is in the PCI bus with either sending commands or retrieving data.  How many PCI devices do you have in this system?  If the data is incorrect then perhaps there is an issue with the synchronization signals themselves (Sample Clock Timebase, Synch Pulse, and AI Start Trigger).

Also since DAQmx 8.0, you can make multidevice tasks with DSA devices.  This means that you can make one task, and include multiple devices in the channel list.  DAQmx will take care of all synchronization routing for you.

Multdevice Task Support For DSA and SMIO

Try it out (if you are not already) and let me know if it makes any difference.

Best Regards,

Jeff Tipps
Applications Engineer
National Instruments

[TroyR]

Hi Jeff,

Thanks very much for your reply. Interestingly the behaviour (~8sec delay) seems to have gone away. I believe your assessment is correct. I am using a Magma PCI expansion bus with my laptop and I think the issue may have been there. Last night when I restarted everything, the delay no longer occurred. Hopefully, it has resolved itself.

Thanks again for the help,

Troy

[wired]

Interesting... I'm seeing an ~8 second delay with two PXI-6120's, but only when they are in certain slots.

[Jeff_T.]

Hello Wired,

How fast are you sampling your data?  Also in which slots are you experiencing this delay?

Thanks,

Jeff Tipps
Applications Engineer
National Instruments

[wired]

I'm having problems with the PXI-bus.  I'm using an 8-slot 1042Q chassis, and I have problems when trying to use slots 5&6 together, or slots 7&8 together.  With outher slot combinations, I can stream all 4 channels from each of two PXI-6120 boards at 800Khz sample rate.  See the following thread for more info:

https://forums.ni.com/t5/PXI/Streaming-from-multiple-devices-fails-if-in-certain-slots/m-p/503566