RE: Extending EDM's supported PVs/data acquisition protocols

["Chestnut, Ronald P." <ronc@slac.stanford.edu>]

Dear Carl,

At SLAC, we needed to interface EPICS to a legacy system. Our solution (in 1997) was to make a Channel Access Server which has access to the legacy system, and responds properly to Channel Access protocol. The Server part of the EPICS Gateway is a piece, with the Client part replaced by legacy system access. This approach is not perfect, but has been in use for a decade.

There are, indeed, interesting problems, such as mapping naming conventions, supporting monitoring, and supplying the ancillary data.

This allowed us to use all the EPICS tools (notably StripTool at the onset) and not just a display manager. You might consider this approach.

Ron Chestnut 

-----Original Message-----
From: tech-talk-bounces@aps.anl.gov [mailto:tech-talk-bounces@aps.anl.gov] On Behalf Of Carl Schumann
Sent: Wednesday, August 20, 2008 12:01 PM
To: tech-talk@aps.anl.gov
Subject: Extending EDM's supported PVs/data acquisition protocols

Hi,

The E in EDM stands for extensible as I understand it.   There are two 
ways that I could think of a display manager(DM) being extensible:
1. extending the widget set
2. extending the set of PVs/data acquisition protocols supported by the DM My interest is doing the later without having to reimplement a whole new widget set as well.

We have users (mostly physicists and engineers but not programmers) doing development with EDM (and EPICS) that are unable to access useful 
machine parameters that are currently only available through ACNET.   
Here at FNAL we will probably never be an exclusively EPICS installation, because of the volume of machine parameters that are 
instrumented via home-grown ACNET.   I would like to extend EDM so that 
it can display legacy ACNET machine info in addition to EPICS machine 
info.   It would appear this would be possible at some level, since it 
appears EDM already supports EPICS and CALC PVs.   Is it 
reasonable/possible to extend EDM to support other "PV"s besides EPICS 
and CALC?   What is not clear so far to me is how much coupling there is 
between the widget set and the PV implementations.   Assuming I can 
develop an ACNET PV for EDM, would I also need to develop an ACNET widget set?

Thank you for your time.

Sincerely,
Carl Schumann