Re: caget for base7 records

["Johnson, Andrew N. via Tech-talk" <tech-talk at aps.anl.gov>]

Hi Sandeep,

On Jul 20, 2020, at 7:31 AM, Sandeep Kumar Malu - UKRI STFC via Tech-talk <tech-talk at aps.anl.gov> wrote:

Is there any way to access V7 records using caget? I am aware that “QSRV” does the pvget(pvaccess) for V3 records but other way around is not possible i.e caget(channel access) for V7 records.

What do you mean by a “V7 record”?

QSRV is an optional module that makes EPICS IOC records accessible over the PV Access (PVA) network protocol. Most IOCs are built with the RSRV module which makes the IOC's records accessible over the Channel Access (CA) network protocol, although it is possible to build an IOC that doesn’t contain RSRV. Thus RSRV and QSRV are just server layers that sit on top of the IOC, and most IOCs support Channel Access by default.

PVA was designed to be a successor to the CA protocol and provides a superset of the capabilities of CA. The pvget/pvput/pvmonitor/pvcall programs speak PVA over the network by default, but they can be asked to speak CA instead. The caget/caput/camonitor programs can only speak CA over the network and this will never change.

If your “V7 records” come from a PVA server which is not an IOC, that server could also be taught to speak CA, but it could be quite a lot of work depending on what language it was coded in. For C/C++ the Portable Channel Access Server library provides the necessary software, and there are other similar APIs for various other languages. However I would recommend that you describe what you’re trying to do in a bit more detail here before going too far into implementing that.

HTH,

- Andrew

-- 

Complexity comes for free, simplicity you have to work for.