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<== Date ==> | <== Thread ==> |
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Subject: | RE: Going full PVA? |
From: | Stainer Tom via Tech-talk <tech-talk at aps.anl.gov> |
To: | "tech-talk at aps.anl.gov" <tech-talk at aps.anl.gov> |
Date: | Wed, 9 Jun 2021 13:30:51 +0000 |
Dear Ralph, Do you mean PVA to CA when writing through that IOC? That works when the QSRV mapping is done in the right way (which is not always trivial). Or another IOC that maps a device speaking PVA into a flat CA control system namespace? Don't really know. I meant the former. It is just entirely clear to me how you would implement this in practice. Do you happen to know of any example code or associated documentation that I can use as a baseline on how to use QSRV to do this? Kind regards, Tom From: Tech-talk <tech-talk-bounces at aps.anl.gov>
On Behalf Of Ralph Lange via Tech-talk On Wed, 9 Jun 2021 at 12:15, Stainer Tom <Tom.Stainer at sckcen.be> wrote:
Correct.
Well, in a way, yes, nah, almost. The database is the database. CA (client) to database mapping is handled by link support calling into the CA client library. Database to PVA mapping is done inside QSRV.
Do you mean PVA to CA when writing through that IOC? That works when the QSRV mapping is done in the right way (which is not always trivial). Or another IOC that maps a device speaking PVA into a flat CA control system namespace? Don't really know.
That kind of mapping can be done in QSRV, where you can basically create a structure by pointing leaves to record fields in the database. Again: you're mapping the elements of a PVA structure that QSRV serves up to fields of records in the EPICS database. CA is not involved on this end. The fact that records can use CA to connect to other IOCs (or other devices running a CA server) is unrelated. Your clients connect to a normal EPICS IOC using PVA, and you're effectively using CA as a field bus below the IOC, conceptually similar to Modbus, SCPI, EtherCAT, OPC UA, ... Cheers, |