RS-422 PPS Signal Generation

[jmk75]

I'm trying to generate a RS-422 PPS signal using the PXI-8431/8 PXI board, LabWindows/CVI and the standard CVI library functions but I can't find a way of producing a signal that remains HI persistently for X number of ms.  I realize that using the PXI-6602 would be an ideal solution but for my case I'm relying on the RT OS to maintain determinism.  Do you know of a white paper or discussion thread that might describe a reliable way of doing this with the CVI functions and serial boards I have?

This post was copied from the LabView discussion board.  Sorry for the inconvenience.

[Adam G]

Hello,

I do not believe that there is a way to do this. The driver doesn't support the toggling of the lines, especially with the accuracy you would need. It would be best to use the PXI-6602 card for this. Have a great day!

Best Regards,

Adam G 

[jmk75]

So I've got my hands on the 6602 and am looking for example code to get me started, but all I can find are dated version (5.5 or earlier).  Is there anything current that could offer some guidelines for generating the PPS?  Specifically, I'm using a RT Hypervisor controller and building an RT application.

Thank you for your help.

[Sean_F]

Hi There,

Assuming you're using DAQmx and you want to generate a continuous pulse train (hardware-timed), you can find examples that do exactly this by looking in: Start » All Programs » National Instruments » NI DAQ » Text-Based Code Support » Ansi C Examples » Counter » Generate Pulse.

Hope this helps!

Sean

[jmk75]

I tried the files you recommend (plus some other examples from various locations) and I keep getting a series of error messages:

Undefined symbol '_RegisterWinMsgCallback@24' referenced in "dataacq.lib".

Undefined symbol '_UnRegisterWinMsgCallback@4' referenced in "dataacq.lib".

Undefined symbol '_GetCVIWindowHandle@0' referenced in "dataacq.lib".

Some files that the example includes are:

NIDAQEX.C

NIDAQEX.H

These all go away when I boot into Windows.  I have loaded the Real-Time module and am using a RT Hypervisor controller.  Could I be missing software or be using a Windows library when a RT lib is available?

Thanks.

[jmk75]

One additional note:

I can include dataacq.h in my RT application code and it compiles fine.  I begin seeing errors when I add the CVI function from the Traditional DAQ library, ICTR_Setup().

[Sean_F]

Hi JMK,

You can use DAQmx or TDAQ, not both. I would strongly recommend DAQmx since TDAQ is no longer supported.

Sean

[jmk75 · Accepted solution]

Sean,

I updated the pulse generation functions with those from the DAQmx library and am now up and running.

Thank you so much for the input.

J

[Sean_F]

Hey Jmk,

Glad to hear it. Happy coding!

Sean