Installing EPICS on the Raspberry Pi¶

For those who haven’t heard, EPICS (http://www.aps.anl.gov/epics) is an open-source control system used worldwide for the routine operation and control of many particle accelerators such as FermiLab and SLAC, for the operation of scientific telescopes such as the Gemini and Keck telescopes, X-ray synchrotrons such as the Advanced Photon Source and the Diamond Light Source, neutron diffraction facilities such as the Spallation Neutron Source, and lots of other neat stuff. The system is scalable and runs on lots of different hardware. Here, we show you how to run EPICS on the Raspberry Pi!

Contents

Raspberry Pi Distribution
Preparing for EPICS
EPICS Base
synApps
PyEpics
Files

Here is how I installed the Experimental Physics and Industrial Control System software (EPICS) [1] on the Raspberry Pi [2].

The EPICS software is a client/server system. To keep things simple, we will run both the server and a client on the Raspberry Pi. (Clients on other computers on our LAN might be able to interact with our EPICS server as well but we will not discuss that now.)

The EPICS server we will use is built in several parts:

EPICS Base provides all the development libraries and a few applications and utilities.
synApps provides additional capabilities that will be useful in real projects. We only use a little of it here, though.

There are many, many possible EPICS clients. Since the RPi already has Python, we’ll work with that:

PyEpics is an EPICS binding to the Python language, allowing us to build a simple client and interact with our server.

[1]	EPICS: http://www.aps.anl.gov/epics

[2]	RPi: http://www.raspberrypi.org/

Raspberry Pi Distribution¶

hardware:	Raspberry Pi, model B, RASPBRRY-MODB-512M [3]
software:	2012-12-16 wheezy-raspbian distribution [4]

Installed wheezy-raspbian distribution on a 16 GB SD card. (It is helpful, but not necessary, to expand the partition to use the full memory of the SD card using raspi-config before starting X11):

Filesystem	Size	Used	Avail	Use%	Mounted on
rootfs	15G	2.4G	12G	18%	/
/dev/root	15G	2.4G	12G	18%	/
devtmpfs	220M	0	220M	0%	/dev
tmpfs	44M	252K	44M	1%	/run
tmpfs	5.0M	0	5.0M	0%	/run/lock
tmpfs	88M	68K	88M	1%	/run/shm
/dev/mmcblk0p1	56M	17M	40M	30%	/boot

[3]	vendor: http://www.newark.com/jsp/search/productdetail.jsp?SKU=43W5302

[4]	wheezy-raspbian: http://downloads.raspberrypi.org/images/raspbian/2012-12-16-wheezy-raspbian/2012-12-16-wheezy-raspbian.zip

Preparing for EPICS¶

EPICS is flexible about where (which directory path) it is placed. Still, it helps to use standard locations. We’ll build it from a directory in the pi account, but make a link to that directory called /usr/local/epics. You’ll need to open a terminal window:

cd ~
mkdir -p ~/Apps/epics
sudo su
cd /usr/local
ln -s /home/pi/Apps/epics
exit
cd ~/Apps/epics

By making the epics directory in pi account, we will be able to modify any of our EPICS resources without needing to gain higher privileges.

EPICS Base¶

EPICS Base is very easy to build. The wheezy-raspbian distribution already has all the tools necessary to build EPICS Base. All that is necessary is to define the host architecture and then build it.

Downloading¶

The latest stable version of EPICS Base is 3.14.12.3 (3.15 is released but is still not recommended for production use):

wget http://www.aps.anl.gov/epics/download/base/baseR3.14.12.3.tar.gz
tar xzf baseR3.14.12.3.tar.gz
ln -s ./base-3.14.12.3 ./base

Building¶

EPICS base can be built for many different operating systems and computers. Each build is directed by the EPICS_HOST_ARCH environment variable. A command is provided to determine the best choice amongst all the systems for which EPICS currently has definitions. Here is the way to set the environment variable on any UNIX or Linux OS using the bash shell (use either of these two commands, they are equivalent in the bash shell:

export EPICS_HOST_ARCH=`/usr/local/epics/base/startup/EpicsHostArch`
export EPICS_HOST_ARCH=$(/usr/local/epics/base/startup/EpicsHostArch)

We can check this value by printing it to the command-line (remember, we are logged in as root):

echo $EPICS_HOST_ARCH
linux-arm

Good! EPICS base will build for a Linux OS on an ARM architecture. This matches my Raspberry Pi.

Tip

The export command above will be useful for future software development. Add it to the ~/.bash_aliases file if it exists, otherwise add it to the ~/.bashrc file with a text editor (such as nano ~/.bashrc).

Now, build EPICS base for the first time:

cd ~/Apps/epics/base
make

This process took about 50 minutes.

Starting¶

It is possible to start an EPICS IOC at this point, although there is not much added functionality configured. We can prove to ourselves that things will start. Use this linux command:

./bin/linux-arm/softIoc

and EPICS will start with a basic command line prompt:

epics>

At this prompt, type:

iocInit

and lines like these (different time stamp) will be printed:

Starting iocInit
############################################################################
## EPICS R3.14.12.3 $Date: Mon 2012-12-17 14:11:47 -0600$
## EPICS Base built Jan 19 2013
############################################################################
iocRun: All initialization complete
epics>

Congratulations! EPICS Base has now been built on the Raspberry Pi.

Environment Declarations¶

To simplify using the tools from EPICS base, consider making these declarations in your environment (~/.bash_aliases):

export EPICS_ROOT=/usr/local/epics
export EPICS_BASE=${EPICS_ROOT}/base
export EPICS_HOST_ARCH=`${EPICS_BASE}/startup/EpicsHostArch`
export EPICS_BASE_BIN=${EPICS_BASE}/bin/${EPICS_HOST_ARCH}
export EPICS_BASE_LIB=${EPICS_BASE}/lib/${EPICS_HOST_ARCH}
if [ "" = "${LD_LIBRARY_PATH}" ]; then
    export LD_LIBRARY_PATH=${EPICS_BASE_LIB}
else
    export LD_LIBRARY_PATH=${EPICS_BASE_LIB}:${LD_LIBRARY_PATH}
fi
export PATH=${PATH}:${EPICS_BASE_BIN}

Note

We are being a bit cautious here, not to remove any existing definition of LD_LIBRARY_PATH. Also the comparison is a Yoda condition [5], placing the constant term on the left of the comparison. Yoda conditions can reveal accidental assignments at run time. Perhaps not so much in the bash shell, but it’s useful in programming languages.

[5]	Yoda condition: https://en.wikipedia.org/wiki/Yoda_Conditions

After EPICS base has been built, we see that it has taken ~35 MB of storage:

pi@raspberrypi:~$ du -sc base-3.14.12.3
35636  base-3.14.12.3

synApps¶

synApps is a collection of software tools that help to create a control system for beamlines. It contains beamline-control and data-acquisition components for an EPICS based control system.

[6]	synApps: http://www.aps.anl.gov/bcda/synApps/

There are instructions for installing synApps posted online: http://www.aps.anl.gov/bcda/synApps/synApps_5_6.html

Download¶

The current release of synApps (as this was written in 2013-02) is v5.6. The compressed source archive file is available from the BCDA group at APS. The file should be 149 MB:

 wget http://www.aps.anl.gov/bcda/synApps/tar/synApps_5_6.tar.gz
 tar xzf synApps_5_6.tar.gz

Uncompressed and unconfigured, the synApps_5_6 source folder is ~541 MB.

Configuring¶

All work will be relative to this folder:

cd ~/Apps/epics/synApps_5_6/support

Follow the instructions in the README file. These are the changes I made to run on the Raspberry Pi.

file	changes
configure/CONFIG_SITE	no changes
configure/RELEASE	`SUPPORT=/usr/local/epics/synApps_5_6/support` `EPICS_BASE=/usr/local/epics/base`

After modifying configure/RELEASE, propagate changes to all module RELEASE files by running:

cd ~/Apps/epics/synApps_5_6/support
make release

Edit Makefile and remove support for these modules:

ALLEN_BRADLEY

DAC128V

IP330

IPUNIDIG

LOVE

IP

VAC

SOFTGLUE

QUADEM

DELAYGEN

CAMAC

VME

AREA_DETECTOR

DXP

xxx module: reconfigure¶

The xxx module is an example and template EPICS IOC, demonstrating configuration of many synApps modules. APS beam line IOCs are built using xxx as a template.

In xxx-5-6/configure/RELEASE, place a comment on lines 19 and 32 to remove build support for areaDetector in xxx:

#AREA_DETECTOR=$(SUPPORT)/areaDetector-1-8beta1

#IP=$(SUPPORT)/ip-2-13

In xxx-5-6/xxxApp/src/xxxCommonInclude.dbd, place a comment on line 34:

#include "ipSupport.dbd"

Then, in xxx-5-6/xxxApp/src/Makefile, comment out all lines that refer to areaDetector components, such as ADsupport, “NDPlugin*, simDetector, and netCDF, as well as dxp support. Here are the lines I found:

#iocxxxWin32_DBD += ADSupport.dbd  NDFileNetCDF.dbd
#xxx_LIBS_WIN32 += ADBase NDPlugin netCDF
#iocxxxCygwin_DBD += ADSupport.dbd  NDFileNetCDF.dbd
#xxx_LIBS_cygwin32 += ADBase NDPlugin netCDF
#iocxxxCygwin_DBD += ADSupport.dbd NDFileNetCDF.dbd
#xxx_LIBS_cygwin32 += ADBase NDPlugin netCDF
#iocxxxLinux_DBD += ADSupport.dbd  NDFileNetCDF.dbd
#xxx_LIBS_Linux += ADBase NDPlugin netCDF

#iocxxxCygwin_DBD += simDetectorSupport.dbd commonDriverSupport.dbd
#xxx_LIBS_cygwin32 += simDetector
#iocxxxLinux_DBD += simDetectorSupport.dbd commonDriverSupport.dbd
#xxx_LIBS_Linux += simDetector

#xxx_Common_LIBS += ip

Install necessary EPICS Extensions¶

synApps 5.6 requires the msi EPICS extension. First, setup the extensions subdirectory

 cd ~/Apps/epics
 wget http://www.aps.anl.gov/epics/download/extensions/extensionsTop_20120904.tar.gz
 tar xzf extensionsTop_20120904.tar.gz

Now, download msi, unpack, build, and install it:

 wget http://www.aps.anl.gov/epics/download/extensions/msi1-5.tar.gz
 cd extensions/src
 tar xzf ../../msi1-5.tar.gz
 cd msi1-5
 make

Make these additional declarations in your environment (~/.bash_aliases):

export EPICS_EXT=${EPICS_ROOT}/extensions
export EPICS_EXT_BIN=${EPICS_EXT}/bin/${EPICS_HOST_ARCH}
export EPICS_EXT_LIB=${EPICS_EXT}/lib/${EPICS_HOST_ARCH}
if [ "" = "${LD_LIBRARY_PATH}" ]; then
    export LD_LIBRARY_PATH=${EPICS_EXT_LIB}
else
    export LD_LIBRARY_PATH=${LD_LIBRARY_PATH}:${EPICS_BASE_LIB}
fi
export PATH=${PATH}:${EPICS_EXT_BIN}

Install other support¶

The EPICS sequencer needs the re2c package (http://re2c.org/). This is available through the standard package installation repositories:

sudo apt-get install re2c

Building¶

Now, build the components of synApps selected in the Makefile:

cd ~/Apps/epics/synApps_5_6/support
make release
make rebuild

The make rebuild step took about 70 minutes.

PyEpics¶

It is possible to run the PyEpics support from Matt Newville (http://cars.uchicago.edu/software/python/pyepics3/) on the Raspberry Pi!

Preparing Python¶

To simplify installation, we’ll use easy_install (from setuptools).

Note

The additions to the Python installation will be done as root. Here’s how to become root on the default wheezy-raspbian distribution.

sudo su

First, install the setuptools package from the wheezy repository. (Also, as long as we’re here, the ipython shell is very helpful.) Let’s load them both:

sudo apt-get install python-setuptools ipython

Next, we want to know which version of Python will be run:

# which python
/usr/bin/python
ls -lAFg /usr/bin/python
lrwxrwxrwx 1 root 9 Jun  5  2012 /usr/bin/python -> python2.7*

Python 2.7 will be run.

Install PyEpics¶

With the setuptools installed, it becomes simple to install PyEpics (still as root):

easy_install -U PyEpics

The installation will complain about missing EPICS support libraries (libca and libCom). Now, we can address that (still as root):

cd /usr/local/lib/python2.7/dist-packages/pyepics-3.2.1-py2.7.egg
cp /home/pi/Apps/epics/base-3.14.12.3/lib/linux-arm/libca.so.3.14 ./
cp /home/pi/Apps/epics/base-3.14.12.3/lib/linux-arm/libCom.so.3.14 ./
ln -s libca.so.3.14  libca.so
ln -s libCom.so.3.14  libCom.so

Now, exit from root back to the pi account session:

exit

Testing PyEpics¶

First, you might be eager to see that PyEpics will load. Save this code in the file verify.py (in whatever folder you wish, we’ll use /home/pi):

#!/usr/bin/env python

import epics

print epics.__version__
print epics.__file__

Also, remember to make the file executable:

chmod +x verify.py

Now, run this and hope for the best:

./verify.py
3.2.1
/usr/local/lib/python2.7/dist-packages/epics/__init__.pyc

This shows that PyEpics was installed but it does not test that EPICS is working.

Testing PyEpics with an IOC¶

Note

We’ll need to use several tools at the same time. It is easiest to create several terminal windows.

To test that EPICS communications are working, we need to do some preparations.

softIoc¶

The simplest way to do this is to use the softIoc support from EPICS base with a simple EPICS database. Save this into a file called simple.db:

record(bo, "rpi:trigger")
{
        field(DESC, "trigger PV")
        field(ZNAM, "off")
        field(ONAM, "on")
}
record(stringout, "rpi:message")
{
        field(DESC, "message on the RPi")
        field(VAL,  "RPi default message")
}

Note

The file simple.db defines two EPICS records: rpi:trigger and rpi:message. The first record can take the value of 0 or 1, which also have the string values of “off” and “on”, respectively. The second record is a string.

Now, run the EPICS soft IOC support with this database:

pi@raspberrypi:~$ softIoc -d simple.db
Starting iocInit
############################################################################
## EPICS R3.14.12.3 $Date: Mon 2012-12-17 14:11:47 -0600$
## EPICS Base built Jan 19 2013
############################################################################
iocRun: All initialization complete
epics> dbl
rpi:trigger
rpi:message
epics>

camonitor¶

In a separate terminal window, watch the soft IOC for any changes to EPICS PVs we created above:

pi@raspberrypi:~$ camonitor rpi:trigger rpi:trigger.DESC rpi:message rpi:message.DESC
rpi:trigger                    <undefined> off UDF INVALID
rpi:trigger.DESC               <undefined> trigger PV UDF INVALID
rpi:message                    <undefined> RPi default message UDF INVALID
rpi:message.DESC               <undefined> message on the RPi UDF INVALID

Python code¶

Now, let’s communicate with the PVs of the softIoc. Put this code in file test.py:

#!/usr/bin/env python

import epics

print epics.caget('rpi:trigger.DESC')
print epics.caget('rpi:trigger')
print epics.caget('rpi:message.DESC')
print epics.caget('rpi:message')

epics.caput('rpi:message', 'setting trigger')
epics.caput('rpi:trigger', 1)
print epics.caget('rpi:trigger.DESC')
print epics.caget('rpi:trigger')
print epics.caget('rpi:message.DESC')
print epics.caget('rpi:message')

epics.caput('rpi:message', 'clearing trigger')
epics.caput('rpi:trigger', 0)
print epics.caget('rpi:trigger.DESC')
print epics.caget('rpi:trigger')
print epics.caget('rpi:message.DESC')
print epics.caget('rpi:message')

Make the file executable and then run it:

pi@raspberrypi:~$ chmod +x test.py
pi@raspberrypi:~$ ./test.py
trigger PV
0
message on the RPi
RPi default message
trigger PV
1
message on the RPi
setting trigger
trigger PV
0
message on the RPi
clearing trigger
pi@raspberrypi:~$

Note that new messages have also printed on the terminal running camonitor:

rpi:message     2013-01-21 08:20:28.658746 setting trigger
rpi:trigger     2013-01-21 08:20:28.664845 on
rpi:message     2013-01-21 08:20:28.697210 clearing trigger
rpi:trigger     2013-01-21 08:20:28.702967 off

Files¶

These files, described above, are available for direct download:

file	description
`verify.py`	test that PyEpics is installed
`simple.db`	simple EPICS database to test PyEpics communications with EPICS
`test.py`	Python code to test PyEpics communications with EPICS

Delimiters: Parentheses, Braces, and Back-Quotes¶

In the code examples above, a combination of parentheses, braces, and back-quotes (a.k.a. accent grave or backtick) are used.

In the /bin/bash shell, braces, { and }, are used to delimit the scope of symbol names during shell expansion. In the code examples above, the delimiters are probably unnecessary. Using these delimiters is a cautious practice to adopt. Parentheses are not recognized in this context:

~$ echo $EPICS_ROOT
/usr/local/epics
~$ echo ${EPICS_ROOT}
/usr/local/epics
~$ echo $(EPICS_ROOT)
EPICS_ROOT: command not found

However, in the various files and commands that configure and command the EPICS components, parentheses, ( and ), are the required delimiters. See these examples from above:

#AREA_DETECTOR=$(SUPPORT)/areaDetector-1-8beta1
#IP=$(SUPPORT)/ip-2-13

Sometimes, in a shell script, it is necessary to assign a variable with the value obtained from a command line tool. One common way to do that, shared by bash and some other shells such as tcsh, is to enclose the command line tool with the ` back-quote character. See this example:

~$ echo $SHELL
/bin/bash
~$ echo `/usr/local/epics/base-3.14.12.3/startup/EpicsHostArch`
linux-x86_64

An alternative way to do this assignment in bash was pointed out, to use shell expansion with parentheses as the delimiters, such as:

~$ echo $(/usr/local/epics/base-3.14.12.3/startup/EpicsHostArch)
linux-x86_64

Installing EPICS on the Raspberry Pi¶

Raspberry Pi Distribution¶

Preparing for EPICS¶

EPICS Base¶

Downloading¶

Building¶

Starting¶

Environment Declarations¶

synApps¶

Download¶

Configuring¶

xxx module: reconfigure¶

Install necessary EPICS Extensions¶

Install other support¶

Building¶

PyEpics¶

Preparing Python¶

Install PyEpics¶

Testing PyEpics¶

Testing PyEpics with an IOC¶

softIoc¶

camonitor¶

Python code¶

Files¶

Delimiters: Parentheses, Braces, and Back-Quotes¶

Table Of Contents

This Page

Navigation

Installing EPICS on the Raspberry Pi¶

Raspberry Pi Distribution¶

Preparing for EPICS¶

EPICS Base¶

Downloading¶

Building¶

Starting¶

Environment Declarations¶

synApps¶

Download¶

Configuring¶

xxx module: reconfigure¶

Install necessary EPICS Extensions¶

Install other support¶

Building¶

PyEpics¶

Preparing Python¶

Install PyEpics¶

Testing PyEpics¶

Testing PyEpics with an IOC¶

softIoc¶

camonitor¶

Python code¶

Files¶

Delimiters: Parentheses, Braces, and Back-Quotes¶

Table Of Contents

This Page

Quick search

Navigation