Experimental Physics and
Industrial Control System

Gabriel Fedel via Tech-talk <tech-talk at aps.anl.gov> · Mon, 24 Jul 2023 09:15:57 +0200

On 7/22/23 18:13, Michael Davidsaver wrote:

On 7/21/23 00:42, Gabriel Fedel via Tech-talk wrote:

Hi Tech-Talk,

I'm playing a bit with the NTEnum

(https://docs.epics-controls.org/en/latest/specs/Normative-Types-Specification.html#ntenum), and I'm wondering if would be possible to use a string as the input so I would get its index.

Something like:

pvput PVEnum "ABC"

This is what should happen now.

I'm failing to get this behavior.

I'm playing a bit with this example (from here -

https://github.com/epics-base/pva2pva/blob/master/iocBoot/iocimagedemo/ntenum.db)

:

record(longout, "$(P):ENUM:INDEX") {
    field(VAL, "1")
    field(PINI, "YES")
    info(Q:group, {
        "$(P):ENUM":{
            +id:"epics:nt/NTEnum:1.0",
            "value":{+type:"structure", +id:"enum_t"},
            "value.index":{+type:"plain", +channel:"VAL", +putorder:"0"},
            "":{+type:"meta", +channel:"VAL"}
        }
    })
}

record(aai, "$(P):ENUM:CHOICES") {
    field(FTVL, "STRING")
    field(NELM, "64")
    field(INP , {const:["ZERO", "ONE"]})
    info(Q:group, {
        "$(P):ENUM":{
            +id:"epics:nt/NTEnum:1.0",
            "value.choices":{+type:"plain", +channel:"VAL"}
        }
    })
}

---
I included putorder on the INDEX, the only behavior I could have was :

* I can pvput to ENUM:INDEX (an integer), and when a read the ENUM I

get the choice

* I can "pvput ENUM value.index=0" and then when I pvget I get the choice

I tried to include a new stringout record to be my "string index" but

also didn't work.

Am I considering a non-valid use case for the NTEnum ?

NTEnum is a bit awkward as it requires that clients be aware of
value.index and value.choices.  In the specific case of pvput
the code involved is here.

https://github.com/epics-base/pvAccessCPP/blob/581d100a029e6f68f3c1830b90509b3ee5ebd7a0/pvtoolsSrc/pvput.cpp#L180-L202

Note that this code is triggered when field being written is a
sub-structure with ID "enum_t".  So it isn't limited to NTEnum.

pvget PVEnum
return : 5

"pvget PVEnum value.index" would print the numeric index.

I couldn't make this pvget syntax works. Actually, I'm not sure how to

get one specific field using pvget.

I'm using this db as a start point:

https://github.com/epics-base/pva2pva/blob/master/iocBoot/iocimagedemo/ntenum.db

Thanks in advance
Cheers

--
Gabriel Fedel
Embedded Software Developer  / Integrated Control System Division

European Spallation Source ERIC
P.O. Box 176, SE-221 00 Lund, Sweden
Visiting address: Partikelgatan 2, 224 84 Lund
Mobile: +46 72 179 23 01
E-mail: gabriel.fedel at ess.eu
ess.eu

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System