Experimental Physics and Industrial Control System (EPICS)

• EPICS is a set of software tools which work together to form a versatile distributed control system. The software consists of a multi-layered structure, spanning the upper-level windows style graphical user interface(GUI), down to the low-level instrument control protocols. The software is run on separate machines (called Input/Output Controllers or IOCs) which communicate using the Channel Access (CA) network protocol. The APS uses around 200 IOCs. The parameters from these IOCs may be displayed and controlled from anywhere in the APS or indeed the world.

• EPICS was originally written by Argonne National Laboratory and Los Alamos National Laboratory, but is now run by many scientific facilities around the globe. It is most commonly used by synchrotrons and observatories.

• EPICS was designed to be easily upgradeable and highly stable. The IOCs run for months between reboots. There are libraries of software drivers which are written and shared throughout the community. These drivers are necessary for the implementation and integration of new hardware, such as a motion controller or a detector.

• EPICS is now capable of running on a number of platforms such as vxWorks, GNU/Linux, Solaris, Windows NT/2000 and RTEMS. EPICS is available under an open source license. The main components may be downloaded from the APS web site, www.aps.anl.gov/epics.

EPICS Basic Components

• The software is separated in to two main components. The first being EPICS Base, which forms the fundamental infrastructure upon which the control system is run. Base defines all the commands and the programming rules used when creating a control system. The second half is a collection of control system tools called records. A complementary set of synchrotron specific modules called synApps, may be downloaded from the APS site.

Control System Creation

• The GUIs (Graphical User Interface) most commonly employed within the EPICS environment are created using a package called MEDM. This enables you to make interactive screens which interface with the control system process variables. There are two complimentary tools available to the control system programmer. The first is an object oriented language which creates a program called a Database using a number of objects called Records. There is a library of Records which perform a range of functions. It is the links between these functions which form the control system. The second tool is State Notation Language (SNL). This language which is similar to C, may be used instead of, or to complement, the Database system.

Useful Links

To the APS EPICS main page,

http://www.aps.anl.gov/epics/

To the APS MEDM main page, http://www.aps.anl.gov/epics/extensions/medm/index.php

To the APS synApps main page, http://www.aps.anl.gov/aod/bcda/synApps/index.php

Los Alamos National Laboratory EPICS main page, http://mesa53.lanl.gov/lansce8/Epics/epics.htm

For more information & full specification contact IDT.