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

[Anders Lindh Olsson via Tech-talk <tech-talk@aps.anl.gov>]

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

 

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