Each accelerator control system has a variety of measurement devices. One of
the most common types of instrument interfaces used for their control is a
serial (RS-232) bus. It is inexpensive and adequate for relatively simple
measurement and control devices such as switchers, amplifiers, voltmeters, and
steppermotors. Since the RS-232 specification is very broad and does not
require uniformity above the basic communication protocol level, one of the
major problems associated with the use of RS-232 is that the command protocol
for each device is unique. This makes it difficult to design generic drivers
for RS-232 and also hampers efforts to design generic troubleshooting methods.
This paper presents software developed independently at three other labs and
integrated into a single system at Jefferson Lab to handle serial devices in a
generic manner. The software is based on the EPICS toolkit and uses a 3-tier
architecture including a common serial driver at the bottom, a top-level
protocol to specify individual device commands in a generic manner, and a
mid-level of software to "glue" the two together.Comment: 3 pages, paper presented at Conference ICALEPCS-2001, San Jose, CA,
November, 200