Re: Mapping customised pva structures to epics v4 Normative Types and v3 PVs (channel access).

[Heinz Junkes via Tech-talk <tech-talk@aps.anl.gov>]

Hi,

I have now chosen NTTables instead of a custom structure in order to at least make ArchiverApplianc happy.

(p4ptest) epics@epics-spielwiese:~/FHI/TEST_PVA$ pvinfo TEST:LLPG
TEST:LLPG
Server: 10.0.0.40:5075
Type:
    epics:nt/NTTable:1.0
        string[] labels
        structure value
            ushort[] Ch
            ushort[] Width
            ushort[] Delay
            ushort[] ExtraDly
            ushort[] Atten
        string descriptor
        alarm_t alarm
            int severity
            int status
            string message
        time_t timeStamp
            long secondsPastEpoch
            int nanoseconds
            int userTag

(p4ptest) epics@epics-spielwiese:~/FHI/TEST_PVA$ pvget  TEST:LLPG
TEST:LLPG <undefined>
Ch Width Delay ExtraDly Atten
 1  1000   100       10     1
 2  2000   200       20     2

Unfortunately, I am unable to set individual values in the table using pvput. I can only address everything:

epics@epics-spielwiese:~/FHI/TEST_PVA$ pvput TEST:LLPG value.Ch="[3,4]" value.Width="[111, 222]" value.Delay="[11, 223]"  value.ExtraDly="[11, 22]"  value.Atten="[1331, 2232]”

Old : 2025-08-14 16:22:29.599
Ch Width Delay ExtraDly Atten
 3   111    11       11  1111
 4   222   223       22  2232
New : 2025-08-14 16:22:35.699
Ch Width Delay ExtraDly Atten
 3   111    11       11  1331
 4   222   223       22  2232

I also have no idea how I can then address the individual fields in Phoebus.

Heinz

> On 13. Aug 2025, at 11:24, Anders Lindh Olsson via Tech-talk <tech-talk@aps.anl.gov> wrote:
>
> Hello,
>  On your question:
> >> Now the question to the group: Is there a better way? And how would you implement my idea?
>  I would map the data structure of the system to EPICS rather than the other way around. So I would compose PVs like FHIFEL:llpg_1:Ch1-Width, FHIFEL-llpg_1:Ch1-Delay, etc.
>   Cheers
> Anders
>  On 2025-08-13, 07:27, "Tech-talk" <tech-talk-bounces@aps.anl.gov> wrote:
> Guten Morgen,
>  One thing that has been on my mind for a long time:
>  We have developed our own devices such as llrf generators, pulse generators, etc., which run on a Raspberry Pi or BeagleBone Black as a management interface.
> We then use p4p on that devices and offer the data points in a pva structure tailored to the respective device.
>  E.g.
>  (base) hactar:~ junkes$ pvinfo  FHIFEL:llpg_1
> FHIFEL:llpg_1
> Server: 141.14.134.173:5075
> Type:
>     structure
>         ushort Ch1_Width
>         ushort Ch2_Width
>         ushort Ch1_Delay
>         ushort Ch2_Delay
>         ushort Ch1_ExtraDly
>         ushort Ch2_ExtraDly
>         ushort Ch1_Atten
>         ushort Ch2_Atten
>   epics@felpvagate:~$ pvinfo FHIFEL:bbamp_1
> FHIFEL:bbamp_1
> Server: 10.0.0.110:5075
> Type:
>     structure
>         boolean ITLK
>         boolean TRIG
>         boolean PWR
>         boolean STAT
>         double SWR
>         double FWD
>         double REV
>         byte RFIN
>         double TSET
>         double TMEAS
>         int PIDI
>         int PIDV
>         boolean TTHI
>         boolean PIDLU
>         double PID_PWR
>         boolean CLRER
>  Now we are experiencing some issues with it.
>  1.) The ArchiverAppliance cannot archive these PVs.
> 2.) Our 'old' Save&Restore supports channel access only.
>  How should we best deal with this?
>  My current idea is to implement a service (Python?) that reads this user-defined structure with pva, breaks down the structure into individual NT-pvs and offers these 'individually' via pva (for the Archiver Appliance, for example) and, at the same time, also offers these PVs as ca-PVs for channel access (for our Save&Restore).
>  Now the question to the group: Is there a better way? And how would you implement my idea?
>  Danke Heinz
>  ------------------------------------------------------------------------------
> Fritz-Haber-Institut    | Phone:         (+49 30) 8413-4270
> Heinz Junkes             | Fax (G3+G4):   (+49 30) 8413-5900
> Faradayweg 4-6        | VC: https://zoom.fhi.berlin/junkes
> D - 14195 Berlin        | E-Mail:        junkes@fhi-berlin.mpg.de
> ------------------------------------------------------------------------------
> “Sorry I’m a bit late, had a terrible time…
> All sort of things cropping up at the last moment. Uh, how are we for time?”
> —Zarquon's address to Milliways

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