Add timestamp to FPGA output

[stevensung]

Hello folks,

Now I have one following question and hope to get answers from you.

I have one NI 6683H GPS module and one NI PXIe-7858R modules both plugged in a PXIe chassis. What I would like to see is

• have sinewave output from AO channels on 7858R modules continuously
• store these waveform data in DMA and store them in a sequence of data files
• have GPS synchronized timestamp associated with every data point in these data files

The first two tasks seem rather straightforward but the last one doesn't. With my limit knowledge of the 6683H module, what I could think of should be something like this example code,

So my question is, is it possible to assign the "Input Terminal" to the starting trigger of the FPGA waveform output assuming that is accessible from the 6683H? By doing that I should then be able to read the timestamp of this starting trigger terminal calculate all consequential timestamp values of waveform output points using the programmed loop rate.

If this works, then I could go further to add one pulse train to the waveform output on FPGA. The pulse train will toggle the output state each time the FPGA outputs a waveform point. Then I could try to read multiple timestamps to get all I need at the end of the waveform output, without additional timestamp calculation.

But first I need your advice to see if this is a working solution or not.

Thanks a lot in advance.

[Bob_Schor]

I realize this does not directly answer the question you asked, and beg your indulgence ...

If you are running a PXIe chassis and running a Real-Time OS on that chassis, and you are acquiring Waveform data using the (very accurate) crystal clock that I assume is plugged into your Chassis, then you should save your data as a Waveform which needs only a single TimeStamp to set the t0 element of the first Waveform.  Granted, if you are acquiring continuous data over weeks (and filling up a lot of disk space), you might "drift" slightly with respect to the GPS module, but you could resynch once a day.

Bob Schor