Synchronizing AO on multiple PCI-6115s with Labview

[SkiClrdo]

Hello, I am trying to generate two channels of sine wave output on two PCI-6115s (4 total output channels).  I am having trouble synchronizing the output between the two boards.  I think the best way for me to do this is to route the board 1 clock to board 2 (possibly along with another trigger?).  As simple as it seems this should be, I am having trouble doing it with Labview.  I have connected the RTSI lines of both boards and attempted to route the board 1 clock over the RTSI with routesignal.vi .  I then configure the AOstart.vi for board 2 to use the "RTSI connection" as a clock source.  It doesn't seem to work.  Any help would be very much appreciated!!  Thanks,  Greg

[Erik_J]

Hi Greg,

Based on what you've said here, it seems that you are using Traditional DAQ.  Is it possible to use DAQmx instead?  DAQmx is more efficient and it will be easier to synchronize S Series cards using DAQmx.

Do you want to output the same sine wave on all 4 channels?  If so, you may not have to use the RTSI cable at all.  Please see the attached VI for how to output the same waveform across multiple devices in DAQmx.

I have included helpful links on DAQmx below.

Transition from Traditional NI-DAQ to NI-DAQmx -- demonstrates how to migrate applications written in Traditional NI-DAQ to NI-DAQmx. It shows the key differences between the two data acquisition (DAQ) drivers and provides some common tips to use while programming in NI-DAQmx.  The document recommends starting with a new VI and using the old VIs written in Traditional NI-DAQ as a guide.
http://zone.ni.com/devzone/conceptd.nsf/webmain/82a34ea5258568d386256de10058912a

Answers to Frequently Asked Questions about NI-DAQmx and Traditional NI-DAQ (Legacy)
http://zone.ni.com/devzone/conceptd.nsf/webmain/ee47b125bb9e053686256fbc0014c384

Learn 10 Functions in NI-DAQmx and Solve 80% of Data Acquisition Applications
http://zone.ni.com/devzone/conceptd.nsf/webmain/40522A58794A358B86256E7B006B8D69?opendocument&node=10119_US

Advantages of NI-DAQmx
http://zone.ni.com/devzone/conceptd.nsf/webmain/B1C2A3BC3228AEA186256D2500640D52?opendocument&node=10119_US


If you must use Traditional DAQ and/or you want to output different waveforms on the different channels, please let me know.

Have a great day!
- Erik

[Erik_J]

Hi Greg!

I should clarify, you do need a RTSI cable to synchronize Analog Outputs.  The example that I posted previously will not actually synchronize the signals.  It is possible however and I am working with our DAQmx Product Support Engineer to create a suitable example.  Please let us know if you must use Traditional DAQ or if DAQmx will work.

Thanks!

- Erik

[SkiClrdo]

Erik,

    Thanks for your replies!  I really appreciate it.  I have been using traditional DAQ.  I am getting a updated version of Labview with DAQmx since it seems everything is going that way.

    I need to generate 4 sine waves with different amplitudes and frequencies.  I am happy to switch my signal generation program over to DAQmx because it is a fairly simple program.  I am simultaneously using a second program that is a software lock-in written in traditional DAQ that is much more complicated and I would prefer not to switch to DAQmx if possible.  Can I run my traditional DAQ lock-in simultaneously with the DAQmx signal generation program?

    Thanks again for the help and I look forward to your the example code you are working on!

Greg

[Erik_J]

Hi Greg,

The following example should get you going in generating a synchronized sine wave on the 4 AO channels across your two 6115s.

I hope this works!

Best Regards,
Erik

[Erik_J]

Hey Greg,

It looks like we posted at the same time.  You can run DAQmx and Traditional DAQ on the same machine as long as you are using different cards.  The example that I attached above uses the same sine wave on all 4 outputs, but it can easily be modified to generate a different sine wave for each output.  Please let me know if you have any more questions.

Have a great weekend!

- Erik

[Lila K]

Erik J,

Would it be possible for you to post this example in LabVIEW 8.0 format?  I am also really interested in looking at it, but I can't open the LabVIEW 8.2 file.

Thanks!

-Lila

[Erik_J]

Hi Lila,

Here is the same VI in LabVIEW 8.0

- Erik

[Nicholas_B]

To synchronize S-Series devices in NI-DAQmx 8.3 you can just put channels from all devices into the same task and they will automatically be synchronized.  This feature is unique to S-Series devices.  So when you configure your DAQ Assistant or DAQmx Channel.vi, add each and every channel from all of your devices that you wish to synchronize.

Please let me know if you have any additional questions....

Regards,

Nicholas B

National Instruments

[Tom_W_[DE]]

Hi All-

To clarify Nick's post- you can NOT use multi-device tasks for analog output with S Series.  The feature Nick described is unique to analog input with S Series and DSA devices.