Experimental Physics and
Industrial Control System

"Faucett, John Allen via Tech-talk" <tech-talk at aps.anl.gov> · Fri, 12 Jun 2020 20:52:02 +0000

There is a proposal that is at least 10 years old but not yet merged into core, though that could happen soon.  It is to use the percent sign (%) to postfix a client-requested filter to a base PV.  A full PV looks like: pv_base%{filter} or pv_base%<filter>.  If an IOC is not built with the software for processing filter subscriptions, there is little chance using % would pose a problem.

By the way, the EPICS filter feature is now being used at LANSCE to allow the client to dynamically specify beam species and time ranges within the beam pulse.  The IOC uses the filter to only forward measurements matching the specified conditions to the client.  This is particularly important for LANSCE since five different beam species are routinely delivered simultaneously to experimental areas.

The filter feature was built into the legacy control system that was designed in the late '60s—it's only taken 50 years for EPICS to catch up!

John Faucett

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System