Experimental Physics and
Industrial Control System

Michael Davidsaver via Tech-talk <tech-talk at aps.anl.gov> · Thu, 17 Dec 2020 12:47:25 -0800

On 12/17/20 11:47 AM, Wang, Andrew via Tech-talk wrote:
> Hi,
> 
>  
> 
> I’m relatively new to EPICS and I have been tasked with writing drivers for a Keysight oscilloscope. One of the commands that I need to set up is the following:
> 
>  
> 
> :CHANnel<N>:SCALe
> 
>  
> 
> This command requires a channel number and a value. So if I wanted to set the vertical scale of Channel 2 to 50 V, I would do
> 
>  
> 
> :CHANnel2:SCALe 50
> 
>  
> 
> I would like to work on both my protocol file and database file, but I am not sure how to go about it. This is what I currently have.
> 
>  
> 
> record(aao, "set_vert_scale")
> 
> {
> 
>               field(DESC, "Set vertical scale for a channel")
> 
>               field(DTYP, "stream")
> 
>               field(FTVL, "STRING")
> 
>               field(OUT, "@keysightOsc.proto setVertScale $(PORT)")
> 
> }
> 
>  
> 
> setVertScale
> 
> {
> 
>               separator = “,”
> 
>               out "%s:SCALe ";
> 
> }
> 
>  
> 
> My goal is for the user to enter a command such as caput set_vert_scale CHAN1,5 so that the string can be split in a manner such that CHAN1 and 5 can be concatenated to the beginning and end of :SCALe.

The usual practice would be for these two logically independent settings
to be made through two different PVs.

eg.

> record(ao, "$(P)Ch$(N):VScale")
> {
>               field(DTYP, "stream")
>               field(OUT, "@keysightOsc.proto setVertScale($N)) $(PORT)")
> }

> setVertScale
> {
>     out ":CHAN\$1:SCAL %f";
> }

This fits nicely with a streamdevice feature to pass parameters
to protocols.  So "\$1" in the .proto file would expand to the value of "$(N)"
from the .db file.  This also lets you load the .db file repeatably
for each channel.

dbLoadRecord("mydigcommon.db", "P=someprefix,PORT=theport")
dbLoadRecord("mydigchan.db", "P=someprefix,PORT=theport,N=1")
dbLoadRecord("mydigchan.db", "P=someprefix,PORT=theport,N=2")
...

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System