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

[Maren Purves <m.purves@jach.hawaii.edu>]

Ned Arnold wrote:
> 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

if you use a mbbo connected to the .SCAN field - and then use the
mbbo in your EDM screen - you can set it so that it only allows
'legal' values for the SCAN period.

HTH,

Maren

>   - 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.