Very Simple Example of EPICS Device Support

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Description

This is a very simple device support example.

This EPICS device support provides the "second" part (00 - 59) of the realtime clock. The EPICS record database provides two records, one-tenth and ten-times of the "second" value.

Building

(use of csh or tcsh is assumed, see below for bash)

invoke following commands to prepare the directory structure and environment.

setenv EPICS_BASE {your-epics-base-directory}
  (for example, setenv EPICS_BASE /proj/epics/R314/R3149/base)
setenv EPICS_HOST_ARCH `$EPICS_BASE/startup/EpicsHostArch.pl`
  ("`" is a back-quote character)
echo $EPICS_HOST_ARCH
  (your platform name is printed like linux-x86_64, darwin-ppc, etc)
$EPICS_BASE/bin/$EPICS_HOST_ARCH/makeBaseApp.pl -t ioc Clock1
$EPICS_BASE/bin/$EPICS_HOST_ARCH/makeBaseApp.pl -i -a $EPICS_HOST_ARCH -p Clock1 -t ioc Clock1

prepare following files copying from a tar file or here.

Clock1App/src/devAiSecond.c
Clock1App/src/devAiSecond.h
Clock1App/src/aiSecond.dbd
Clock1App/Db/aiSecond.db

modify following files, or copy from above tar file or here and here.

Clock1App/src/Makefile
Clock1App/Db/Makefile
iocBoot/iocClock1/st.cmd

then, invoke following commands to build your application.

mkdir log
make |& tee log/clockapp.log
cd iocBoot/iocClock1/
chmod +x st.cmd

Running

invoke following commands to run and test your application.

../../bin/$EPICS_HOST_ARCH/Clock1 st.cmd
epics> dbl
epics> dbpr CO_TEST:CLOCK1:SEC1 4

Using

then, use commands like caget or camonitor to read created records. for example, invoke the following command on another terminal or on another host.

camonitor CO_TEST:CLOCK1:SEC1 CO_TEST:CLOCK1:SEC10

More description

devAiSecond.c provides a device support using ai (analog input) record support. It reads the system clock and extract the "second" part. As it takes only a short time to get the information, the device support is relatively simple. If it takes relatively long time to process input/output, the later part of the process should be postponed in order not to prevent the real-time processing of other part of your ioc application. Such a device support is called an asynchronous device support. The part of the process may be performed in another thread or process, and that is called a driver support. You may write your own asynchronous device support and the corresponding driver support, or you may utilize AsynDriver.

aiSecond.db database defines two process variables. One of them is processed every second (SCAN: 1 second) and reads the realtime clock through the devAiSecond device support. It specifies a linear conversion (LINR: LINEAR, ASLO: 0.1, etc) to have one tenth of the "second" value. It also specifies several alarm conditions (HIHI: 5.5, HHSV: MAJOR, etc), and a MAJOR alram is generated if the value is equal or above 5.5.

aiSecond.dbd binds the record support "ai", the device support name "Second" (used in the database, aiSecond.db), and the dset structure "devAiSecond" (used in the device support, devAiSecond.c).

Further details how to develop EPICS IOC applications are described in IOC Application Developer's Guide.

Building with bash

(use of bash is assumed instead of csh, see above for csh)

invoke following commands to prepare the directory structure and environment.

export EPICS_BASE={your-epics-base-directory}
  (for example, export EPICS_BASE=/proj/epics/R314/R3149/base)
export EPICS_HOST_ARCH=`$EPICS_BASE/startup/EpicsHostArch.pl`
  ("`" is a back-quote character)
echo $EPICS_HOST_ARCH
  (your platform name is printed like linux-x86_64, darwin-ppc, etc)
$EPICS_BASE/bin/$EPICS_HOST_ARCH/makeBaseApp.pl -t ioc Clock1
$EPICS_BASE/bin/$EPICS_HOST_ARCH/makeBaseApp.pl -i -a $EPICS_HOST_ARCH -p Clock1 -t ioc Clock1

prepare following files copying from a tar file or here.

Clock1App/src/devAiSecond.[ch]
Clock1App/src/aiSecond.dbd
Clock1App/Db/aiSecond.db

modify following files, or copy from above tar file or here and here.

Clock1App/src/Makefile
Clock1App/Db/Makefile
iocBoot/iocClock1/st.cmd

then, invoke following commands to build your application.

mkdir log
make 2>&1 | tee log/clockapp.log
cd iocBoot/iocClock1/
chmod +x st.cmd

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