Experimental Physics and
Industrial Control System

Timo Korhonen via Tech-talk <tech-talk at aps.anl.gov> · Fri, 24 Mar 2023 10:00:19 +0000

Hi Érico,

>> P.S.: I couldn't find documentation that specified clearly that JSON links could be used in places like input links for "newer" EPICS
>> releases, outside of the release notes. That might be an interesting hole to plug in the docs. Would it go somewhere like [3]? I could try to
>> tackle it.

A good point, thank you for bringing this up.  The source file for [2] is in the Base distribution, modules/database/src/std/link/links.dbd.pod
in pod (Perl POD) format. In the build process, the document is auto-converted to HTML using some Perl scripts and libraries. 
Even if the file has the .dbd.pod extension, it is pure documentation and contains no dbd definitions or such.

I see two alternatives:
1) as the text is rather "stable", i.e., has not and probably will not change a lot, integrating the text in [3], as you suggest.
2) I have an ambition to extend the build process a bit so that the pod file(s) would be processed and auto-included in RTD documentation, to be visible on docs.epics-controls.org.
However, option 2 has been progressing very slowly as my day job tends to take most of my time...

Integrating the description into [3] would make the usage clearer for users, so that might be the better (and right, IMO) option. 
The document is written and "owned" by Andrew Johnson, so I think he has the decisive vote.

But if we go for option 1 and you are willing to do the editing, please give it a go and make a pull request. It would then go to the docs site after review and merge.
Please let me know if you need instructions on how to proceed.

Best regards,

Timo

On 2023-03-23, 21:18, "Tech-talk on behalf of Érico Nogueira Rolim via Tech-talk" <tech-talk-bounces at aps.anl.gov <mailto:tech-talk-bounces at aps.anl.gov> on behalf of tech-talk at aps.anl.gov <mailto:tech-talk at aps.anl.gov>> wrote:

Hello!

I am using Constant Link Values, as documented in [1], to initialize
some waveforms in my IOC. I'm defining my records as shown below:

record(waveform, "Array-Cte"){
field(FTVL, "LONG")
field(NELM, "4")
field(INP, [1,2,3,4])
}

However, when I use camonitor or pvget to receive their values, I am
notified that their values are, in fact, undefined/invalid:

$ pvget Array-Cte

Array-Cte <undefined> INVALID DRIVER UDF [1,2,3,4]

$ camonitor Array-Cte

Array-Cte <undefined> 4 1 2 3 4 UDF INVALID

If I add field(PINI, YES) to the record definition, I no longer get
notified about invalid values or anything. But it feels wrong to have to
add PINI in this case, since I'm declaring an initializer explicitly,
and it also feels ugly to leave the UDF/INVALID text in the output. Is
this expected behavior?

I am using epics-7 at the tip of master as of today
(5eff3803a83fbc3ea855b63841f5359c09830ade). This happens for waveforms
where FTVL is "STRING" as well, at the very least. It also happens if I
use the "{const: [1,2,3,4]}" syntax from [2].

[1] https://epics.anl.gov/base/R3-16/1-docs/RELEASE_NOTES.html <https://epics.anl.gov/base/R3-16/1-docs/RELEASE_NOTES.html>

[2] https://epics.anl.gov/base/R7-0/7-docs/links.html <https://epics.anl.gov/base/R7-0/7-docs/links.html>

Thank you,

Érico

P.S.: I couldn't find documentation that specified clearly that JSON
links could be used in places like input links for "newer" EPICS
releases, outside of the release notes. That might be an interesting
hole to plug in the docs. Would it go somewhere like [3]? I could try to
tackle it.

[3]
https://docs.epics-controls.org/en/latest/guides/EPICS_Process_Database_Concepts.html <https://docs.epics-controls.org/en/latest/guides/EPICS_Process_Database_Concepts.html>

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Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System