1-D Digital Waveform Questions

[rp_u_of_m]

I'm having some difficulties dealing with the data in the format that my DAQ returns (I'm using a NI USB-6259, if that makes a difference).

Setup:

    I've setup the DAQ to read two digital signals that are connected to the board.  The first is a clock, the second is a data signal.  My goal is to have this data written out to a file, and displayed on a simple chart.  Both signals are fairly slow (in the tens of KHz).  I've already used the "test" functionality of the DAQ assistant to ensure that the connections are correct and the signals are being received properly.

    The DAQ Assistant VI returns the data from the two signals as a single 1-D array of type Digital Waveform.

Questions:

1.) I would like to write out the data from the DAQ to a spreadsheet.  I've been trying to use the "Array to Spreadsheet.vi" to write the data out to a file, but I get a "This wire connects to a polymorphic terminal that cannot accept this data type error", and I'm not sure why.  I thought that this VI was supposed to accept any type of array, or is there some type of conversion that I have to do first?

2.) Since the above method didn't work, I tried using the "Write LabVIEW measurement file" VI, but it only will accept data into the signal port that is of type "Dynamic Data", and I'm not sure how to configure the "convert to dynamic data" VI to properly transfer the 1-D array of Digital Waveform into Dynamic Data.  Does anyone know how to do this?

3.) Finally, is there a way to get the waveform chart to behave like an oscilloscope?  I've set the window width and changed the update mode to "scope", but the display still is the same as when I set it to "sweep".  Is there some other setting I need to adjust to get the display to mimic that of an oscilloscope?

Help with any of the above questions would be greatly appreciated.


Thanks,

Randy

[JLS]

Hello,

Let me address your questions; 1 and 2 are really centered around the same idea, so I'll group those two:

Questions 1 and 2

The digital waveform datatype is much like a cluster - it contains components which must be "unbundled."  You can do the "unbundling" with the Get Digital Data Components function from the Digital Waveform palette.  From there you can expose the relevant underlying data which you can write to file etc. 

Question 3

The update modes of charts are definitely distinct - perhaps it's hard to tell given the data you have, but here are the official descriptions/behaviors as documented in the LabVIEW Help:

Strip—Shows running data continuously scrolling from left to right across the chart with old data on the left and new data on the right. A strip chart is similar to a paper tape strip chart recorder.

Scope—Shows one item of data, such as a pulse or wave, scrolling partway across the chart from left to right. For each new value, the chart plots the value to the right of the last value. When the plot reaches the right border of the plotting area, LabVIEW erases the plot and begins plotting again from the left border. The retracing display of a scope chart is similar to an oscilloscope.

Sweep—Works similarly to a scope chart except it shows the old data on the right and the new data on the left separated by a vertical line. LabVIEW does not erase the plot in a sweep chart when the plot reaches the right border of the plotting area. A sweep chart is similar to an EKG display.

I hope this helps!

Best Regards,

JLS