Onboard device memory underflow error

[PompoCZ]

Hi all,

I'm trying to generate signal via analog output of my USB-6259 DAQ. The signal is generated into 1D array and then segmented to 64 parts with same length to 2D array. DAQmx Write writes to the output one row of this 2D array, the row is selected depending on the index of while loop. I chose this approach so I should be able to stop the VI after arbitrary segment is written to the output. I run this task in Continuous samples mode and with disabled regeneration to get rid of glitches on the output.

I need to write to the output 20 samples per loop iteration with 64kHz sampling rate. My problem is that when I run the DAQmx write VI I get the 200621 error "Onboard device memory underflow". Do you have any ideas how can I get rid of this error? I've seen this error for the first time today, the VI worked fine before.

The corresponding part of code is attached in the zip below, name of the main VI is "MAIN_chopper.vi" and the problematic task is called "CLK_out_task". The error appears after the play button in "main controls" cluster is pressed.

Cheers

Pompo

[Zody]

Hi Pompo,

Welcome on NI Forum.
As the error states, your memory is underflow, that means you are not writing fast enough to the memory.

I would suggest to extract it separately and test your logic. 

Why do you get the glitches as the output if you use regeneration mode? If you make sure that you have full periods of your signal in the memory, you shouldn't see any glitches.

You can use the example from this link, to test if you have any glithches or not. https://decibel.ni.com/content/docs/DOC-4969. Obviously you will have to modify to make the generation continuously.

Best regards,

IR