EPICS: ASYNCHRONOUS DRIVER SUPPORT*

asynDriver [1] is a general-purpose facility for interfacing device-specific code to low-level drivers. asynDriver supports nonblocking device support that works with both blocking and nonblocking drivers. A primary target for asynDriver is EPICS device support, but much of it is independent of EPICS. This paper presents an overview of asynDriver and the range of devices it supports. BACKGROUND The Experimental Physics and Industrial Control System (EPICS) [2] is a set of software tools, libraries, and applications developed collaboratively and used worldwide to create distributed, soft, real-time control systems for instruments such as pa rticle accelerators, telescopes, and other large scientific experiments. EPICS development began around 1990, and over the years, support has been developed for a large variety of hardware devices. This support usually consists of a driver, which communicates with the hardware, and device support for EPICS records. These two components are often linked by a custom-defined private interface. Generic support, in fact several different implementations, has been developed for serial and GPIB devices. The idea of creating asynDriver arose from the desire to provide a more structured environment for developing support for hardware devices and was the result of many years’ experience writing EPICS device and driver support. The initial version of asynDriver supported only asynchronous device communication, i.e., communication that causes the requester to wait. When the synApps [3] X-ray beamline control software package was converted to use asynDriver, support for synchronous device communication was added. asynDriver is now a framework for both asynchronous and synchronous communication with hardware devices. OVERVIEW