File storage of compressed digital waveforms are suggested implemented using the NI-HSDIO vi's as mentioned in http://digital.ni.com/public.nsf/allkb/DDC89A09E7F330E68625726C0067D58F?OpenDocument.
Attached please find an example which explores this solution as it generates a compressed waveform and saves it to a file using the suggested niHWS store/retrieve waveform vi's.
At first glance it works (except that line names are not retained 😞 ) but as soon as the virtual number of samples increase beyond a certain limit the program fails with memory exhaust. With virtual number of samples I mean, that although the number of samples are large, but data do rarely change - a boon for a compressed format where only changes are time stamped.
With the attached example you can explore different combinations of number of change points and deltaTime between them. I suggest in the code to have only 5 change points but long time between them, and at a certain time step the program fails with memory full.
This more than suggests that the niHWS vi's are not optimized for operation on compressed digital waveforms.
The ability to save digital waveforms with scarse changes but huge number of samples is tremendous useful, so if my conclusion is correct I would like to suggest NI to put this on a wish list.
Add to this wish list that the time stamps also support U64 format and not only U32. Because note that an U32 data range exhausts already after about 100 seconds at 40MHz sample rate, which is a typical clock for cRIO FPGA's for instance.
Workarounds and alternatives solutions are welcome.
Henning
Message Edited by heel on 04-14-2010 03:49 PM
Message Edited by heel on 04-14-2010 03:51 PM
Message Edited by heel on 04-14-2010 03:52 PM
