Beckhoff BK9000 support survey

["Dunning, Michael via Tech-talk" <tech-talk@aps.anl.gov>]

At SLAC we use Beckhoff bus terminals quite extensively because they
are inexpensive and reliable, but unfortunately don't yet have a
common epics support solution.  We have at least three versions of
support which were developed independently.

One version uses only the epics modbus module.  This has no driver so
requires less maintenance, but makes setting up IOCs more time
consuming and results in a lot of code duplication.

Another version uses asynPortDriver and some custom modbus code.  This
is designed to make setting up IOCs easier, but requires maintenance
of the driver code.

Another uses custom epics device support.  This requires writing
device support for each bus terminal, and has resulted in a pretty
ugly codebase.  This is our least favored solution going forward.

A typical installation would be a BK9000 bus coupler plus several
analog and/or digital I/O modules (e.g. KL2114, KL1104, KL3172,
KL3314), communicating over ethernet using Modbus TCP.

Before we settle on a solution, we'd like to see what everyone else is
doing.  Any responses would be helpful.

Thank you,
Mike




Michael Dunning
SLAC National Accelerator Laboratory
2575 Sand Hill Road
Menlo Park, CA 94025
(650) 926-5200