Pause waveform to change clock rate

[Sirmutt]

I need to change the clock rate of a waveform I generate without losing the state of the output.  I'd like to pause, adjust the rate, then resume.  Is that possible?

I currently abort, change, and re-initiate, but that starts over at the beginning of the waveform and I lose my position and states.

[Havarti]

Hi SirMutt,

What hardware, labview version, and driver versions are you using?

If you are using an HSDIO device you cannot change the generation speed while generation is initiated. 

If you know what point in the waveform that you need to stop, you can use the Write Position VI to begin where you left off. 

If you need to be able to start and stop at arbitrary points in the waveform it will be a little more difficult.  I have never tried it but you may be able to export your sample clock and count pulses of the sample clock using the start trigger until you stop and use that value as your offset for the Write Position VI.  Or, acquire on the same pins you are generating on so you can see where in the waveform you got to.

Brian

Message Edited by BrianPack on 04-23-2007 12:04 PM

[Sirmutt]

I meant to include that info.  I'm using a PXI-6541 with LabView 8.2.  My waveform is 555,000 samples long and stop/start can be anywhere.  I will need to look into counting where I'm at and starting at that position.

[Raajit_Lall]

Hello SirMutt,

There is actually a VI called niHWS Seek.vi.  This VI moves the single position of the write or read from the HWS file based on the input called relative to and then offset.  You can set the position and offset to whatever position you need in the waveform so that it does not start at the beginning every time.

You can get to this VI in the NI Hierarchichal Waveform Storage Palette > niHWS Low Level Read > niHWS Utility VIs.

Hope that helps.

Regards,