EPICS was initially developed as the Ground Test Accelerator Controls System at Los Alamos National Laboratory in 1988 by Bob Dalesio, Jeff Hill et al. In 1989, Marty Kraimer from Argonne National Laboratory came to work alongside the GTA controls team for 6 months, bringing his experience from his work on the Advanced Photon SourceControl System to the project. The resulting software was renamed EPICS and was presented at the International Conference on Accelerator and Large Experimental Physics Control Systems in 1991. EPICS was originally available under a commercial license, with enhanced versions sold by Tate & Kinetic Systems. Licenses for collaborators were free, but required a legal agreement with LANL and APS. An EPICS community was established and development grew, as more facilities joined in with the collaboration. In February 2004, EPICS became freely distributable after its release under the EPICS Open License. It is now used and developed by over 50 large science institutions worldwide, as well as by several commercial companies.
Architecture
EPICS uses client–server and publish–subscribe techniques to communicate between computers. Servers, the “input/output controllers”, collect experiment and control data in real time, using the measurement instruments attached to them. This information is then provided to clients, using the high-bandwidth Channel Access, or the recently added pvAccess networking protocol, which are designed to suit real-time applications such as scientific experiments. IOCs hold and run a database of "records", which represent either devices or aspects of the devices to be controlled. They can be hosted by either stock-standard servers or PCs, or VME, or MicroTCA standard embedded system processors. For "hard real-time" applications the RTEMS or VxWorksoperating systems are normally used, whereas "soft real-time" applications run onLinux or Microsoft Windows. Data held in the database of records are represented by unique identifiers, known as Process Variables. These PVs are accessible over the channels provided by the Channel Access network protocol. Database records are available for different types of input and output or to provide different functional behaviour such as a calculation record. It is also possible to create custom record types. Each record consists of a set of fields, which hold its data and specify its behaviour. Most record types are listed in the . Graphical user interface packages are available, allowing users to view and interact with PV data through typical display widgets such as dials and text boxes. Examples include EDM, MEDM, and . Any software that implements the CA/pvAccess protocol can read and write PV values. Extension packages are available to provide support for MATLAB, LabVIEW, Perl, Python, Tcl, ActiveX, etc. These can be used to write scripts to interact with EPICS controlled equipment.
