Re: Is there any chance that I can change SCAN parameter dynamically?

[Ned Arnold <nda@aps.anl.gov>]

Chen -

Yes, you can change the SCAN value dynamically.  Options would include:

  - Place a menu widget on your EDM screen assigned to the <fanoutRecord>.SCAN field and have the user interactively set it to the optimum value

  - Add a calcout record in your IOC database that calculates the optimum value (based on your description) and write this value to <fanoutRecord>.SCAN. 

Have fun -

   Ned

On Oct 31, 2007, at 8:50 AM, Zhichu Chen wrote:

Hi all,

It's an interesting story. I've written an EPICS program and gotten it run on an oscilloscope partly successfully and used EDM to get waveforms and set parameters through CA.

What I mean by "partly" is, I used a fanout record to get waveforms from four channels and set it scan periodically, say "1 second," and it works fine unless the time scale is bigger than 0.02---0.02 is fine and 0.05 will make the oscilloscope stun until I set the time scale back to less than 0.05.

Finally, I figure out and set the SCAN field of the fanout record to "5 second" and it works again. So I guess, since time scale is 1/10 of the whole waveform---whose unit is "second"---and there're four waveforms I registered. So it will take 40*timescale to get all I want because I've told that my product---DPO7054---used only one probe for all four channels. Before I get the waveform, the buffer is locked and will never refresh in my case.

I know I can set SCAN to a very big number but, when the time scale is small, I think it's not efficient then. I'm just wondering whether I could use another record to control it, or something alternative.


Thanks for any input.

--
Best Regards
Chen
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          Zhi-chu Chen | Shanghai Synchrotron Radiation Facility
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