How to load a custom waveform for use with DAQ voltage generation

[jamoore84]

I would appreciate some advice on how to take a custom waveform (just a modified triangle wave with pauses at the tops and bottoms) and use that to control the voltage output from a DAQ. 

Some background:  My intent is to use the waveform to control mirror scanning for a LADAR imaging application .  Because our DAQ (NI-6251) only has one clock, it cannot update the X and Y channel voltages independently. I'm using a triangle wave to control both axes, which works fine for the X direction.  However, to prevent the Y axis from incrementally steping up after every X pixel, I'd like to construct a waveform, similar to a step pyramid, so that the Y axis remains constant over the X sweep and only updates to the next row after all X pixels are collected.

I assume I can make the desired plot in excel, and then read it in somehow - but this is where I start to get fuzzy.  Can any one point me to an example or tutorial on this?

Some other questions:

1. Do I needto worry about scaling? will my custom plot need to contain a specific number of points (perhaps the exact number of pixels in the image)?

2. If I change the image dimensions, will I need to revise the control waveform in the Y axis?

Thanks in advance,

jimmy

[Margaret F.]

Hi Jimmy,

Thank you for posting to the NI Forums!! You can certainly create data in Excel, save it to a text file, and then use the Read From Spreadsheet.vi to read the data into LabVIEW. As far as your two concers, I'd like to address those once I understand your application a little more. Would it be possible to attach a paint drawing or something showing what you would like the waveforms to appear as in LabVIEW? This will help me make sure I've followed you correctly. Thanks!

[Need4Speed]

This thread didn't appear to go anywhere.  I am trying to do something similar and was looking for help.  I want to create a repeating output voltage wave based off the excel file attached(with times).  Is there a way to have my program match the output voltage and time with the table attached on a repeat and send that signal to the output?

Thanks,

T

[A_Donfigulation_Error_Has]

Hi Need4Speed,

One way you could do this is to build a waveform using the data. Please see the example "Cont Gen Voltage Wfm-Int Ckt.vi" from Help -> Find Examples -> Hardware Input and Output -> DAQmx -> Analog Generation -> Voltage. The idea is to get your data out of the excel file and into an array and build it into a waveform using the Build Waveform function. Instead of using a sine wave (like in the example) you want to feed the DAQmx write the waveform you created. In your case, d0 would be "0", dt would be "0.0034" and Y would be each Y value.

Jason L