EPICS Data Server Introduction

It is often desirable to provide the HRIBF operators with various types of diagnostic information related to the delivery of beam to a target associated with some experiment. In the past, custom applications have supplied this information using X Windows as the delivery mechanism.

Another method now exists that can be used by an external agent to write directly into an EPICS database. The supplied information may thus be easily integrated into the control system displays according to the preferences of the operators.

Servers

Six servers are available on orib51. Each server may handle only one connection at a time so, currently, only six clients may be run at any point in time. A client connects to a server with a unique port. Available ports are 60000, 60001, 60002, 60003, 60004, and 60005.

Clients

Clients include dataServer.h and use routines contained in dslib.c to communicate with a server. The general structure of a client is given below.

Call dsInit to connect to a server

Call dsAllocatePvs to allocate list of N EPICS PVs for write access

loop {

Obtain N numeric diagnostic values

Encode these numeric values as a character string

call dsWriteAll to write EPICS PVs

call dsDelay to delay

} until finished

call dsFreePvs to free the list of allocated PVs

call dsTerminate to close the connection with the server

EPICS PV Names

Legal PV names must conform to one of the following forms:

scal:acq1:cnt#
scal:acq2:cnt#
scal:acq3:cnt#

scal:rmsacq1:cnt#
scal:rmsacq2:cnt#
scal:rmsacq3:cnt#

scal:drsacq1:cnt#
scal:drsacq2:cnt#
scal:drsacq3:cnt#

# may be 0 through 9

Using any other name will result in an error.

Building Your Client

• Obtain dslib.c, dataServerPriv.h, dataServer.h, and dataServer.version
• Write the code for your client, see client.c as an example
• Modify the makefile shown below; change client, client.c, and client.o to the name of your client files
• make

Example Make File

client : client.o dslib.o
cc –o client –lm client.o dslib.o

client.o : client.c dataServer.h
cc –o client.o –c client.c

dslib.o : dslib.c dataServerPriv.h \

dataServer.h dataServer.version
cc –o dslib.o –c dslib.c