Analog output to the DAQ that changes when controls on the front panel change

Question

I'm using the PCI-6024E, and trying to output an analog waveform that can change when one of the two controls on the front panel change. It outputs fine setting it to continuous output and using a simple while loop around the "Is Task Done" VI, but if I put the "Write" VI in the while loop, it doesn't output steadily. I then tried to use an event structure, so that I'd only have to write every time something on the front panel changes, but for some reason it was writing finite samples, even though I set the Timing VI to continuous. I looked around the NI site, and found an article about this with an example. I tried to change it around to use my waveform, but whenever I run it, I get a memory underflow error. Has anyone needed to do this before? Thanks in advance.
-- Josh Matloff

Answer 1

Hi Josh-
It looks like you forgot to post the code still, but I'll take a stab at the problem anyway. It sounds like you're looking for a way to update a continuous waveform at runtime.
You will need to stop the task in order to replace the write buffer information, but this will only be a small gap in operation. I have attached a modified LabVIEW shipping example that shows how to use value change events for any of the pertinent waveform parameters to either programmatically stop the task, replace the buffer, set timing and restart or to just pass the task information straight through. This will lead to continuous operation with no breaks at the output.
Please let us know if this clears up your questions.
Thanks-
Tom W
National Instruments
Attachments:
Cont Gen Voltage Wfm-Int Clk with Runtime Update.vi ‏134 KB