The pvAccess for Python package requires recent versions of the following software:
- EPICS Base (v3.14.12.3 or 3.15.2)
- EPICS4 CPP release (v4.4.0 or v4.5.0)
- Python development header files/libraries (v2.6.6)
- Boost (v1.41.0); must have the boost_python library built.
- Standard development tools (gcc, make, autoconf, etc.)
- Boost.NumPy (optional, for retrieving numeric scalar arrays as numpy arrays)
- Sphinx (optional, for generating documentation)
The Software versions listed above were used for prototype development and testing. It is likely that any recent version of Python and the Boost libraries (such as those that come with current linux distributions) should work. Similarly, any recent version of EPICS Base that is supported by EPICS4 CPP should be fine. EPICS4 CPP versions newer than v4.5.0 may not work.
Nothing special needs to be done when building the EPICS4 CPP modules. Ensure that the EPICS Base installation you use for this module is the same one that was used to build the EPICS4 modules.
This module has not been adapted for use on Microsoft Windows. Only Unix-like operating systems (e.g. Linux, MacOS, Solaris) are currently supported.
This can be done manually, or using autoconf.
For manual configuration: Read the comments in both the configure/RELEASE and
configure/CONFIG_SITE files and follow the instructions given there.
For automatic configuration: In the top level directory run
$ make configure EPICS_BASE=/epics/base/path EPICS4_DIR=/epics/v4/path [BOOST_NUM_PY_DIR=/boost.numpy/path]In the above command replace /epics/base/path with the full path to your
EPICS Base directory, and /epics/v4/path with the full path to your top level
directory containing the v4 modules pvDataCPP, pvAccessCPP, etc.
Note that the optional BOOST_NUM_PY_DIR argument enables NumPy array support,
and that you can only use the automatic configuration if the v4 modules have
not been renamed.
The make configure command will check for your Boost/Python libraries, and
create suitable configure/RELEASE.local and configure/CONFIG_SITE.local files.
They should look roughly like the examples below:
$ cat RELEASE.local
PVACLIENT = /home/epics/v4/pvaClientCPP
PVACCESS = /home/epics/v4/pvAccessCPP
NORMATIVETYPES = /home/epics/v4/normativeTypesCPP
PVDATA = /home/epics/v4/pvDataCPP
EPICS_BASE = /home/epics/base-3.14.12.5
$ cat CONFIG_SITE.local
PVA_PY_CPPFLAGS = -I/usr/include -I/usr/include/python2.6
PVA_PY_LDFLAGS = -L/usr/lib64 -L/usr/lib64 -lpython2.6
PVA_PY_SYS_LIBS = boost_python-mt
PVA_API_VERSION = 450
PVA_RPC_API_VERSION = 440
HAVE_BOOST_NUM_PY = 0The above files were created automatically on a 64-bit RHEL 6.6 machine, with the following boost/python packages installed:
$ rpm -q boost-python python-devel
boost-python-1.41.0-25.el6.x86_64
python-devel-2.6.6-52.el6.x86_64In the top level package directory run:
$ makeThis will create and install a loadable library named pvaccess.so under the
lib/python directory which can be imported directly by Python.
This also creates setup.sh and setup.csh files in the bin/$EPICS_HOST_ARCH
directory that configure PYTHONPATH for using the pvaccess Python module, e.g.:
$ cat setup.sh
#!/bin/sh
#
# pvaPy sh setup script
#
# modifies PYTHONPATH environment variable
#
if test -z "$PYTHONPATH" ; then
export PYTHONPATH=/home/epics/v4/pvaPy/lib/python/2.6/linux-x86_64
else
export PYTHONPATH=/home/epics/v4/pvaPy/lib/python/2.6/linux-x86_64:$PYTHONPATH
fiThese files must be sourced to use, e.g.:
$ . /home/epics/v4/pvaPy/bin/linux-x86_64/setup.sh
$ echo $PYTHONPATH
/home/epics/v4/pvaPy/lib/python/2.6/linux-x86_64or for csh users:
% source /home/epics/v4/pvaPy/bin/linux-x86_64/setup.csh
% echo $PYTHONPATH
/home/epics/v4/pvaPy/lib/python/2.6/linux-x86_64This step is optional and requires Sphinx to be installed:
$ make docIf a sphinx-build script is present on the system, html pages will be
generated in the documentation/sphinx/_build/html directory.
For simple testing, do the following:
- In a separate terminal, start the testDbPv IOC:
$ cd $EPICS4_DIR/pvaSrv/testTop/iocBoot/testDbPv
$ ../../bin/$EPICS_HOST_ARCH/testDbPv st.cmd- Source the appropriate setup file from pvaPy's
bin/$EPICS_HOST_ARCHdirectory and start python (the Python PVA module is called pvaccess):
$ python
>>> import pvaccess
>>> dir (pvaccess)
['BOOLEAN', 'BYTE', 'CA', 'Channel', 'DOUBLE', 'FLOAT', 'FieldNotFound',
'INT', 'InvalidArgument', 'InvalidDataType', 'InvalidRequest', 'LONG',
'NtTable', 'NtType', 'PVA', 'ProviderType', 'PvAlarm', 'PvBoolean', 'PvByte',
'PvDouble', 'PvFloat', 'PvInt', 'PvLong', 'PvObject', 'PvScalar',
'PvScalarArray', 'PvShort', 'PvString', 'PvTimeStamp', 'PvType', 'PvUByte',
'PvUInt', 'PvULong', 'PvUShort', 'PvUnion', 'PvaException', 'RpcClient',
'RpcServer', 'SHORT', 'STRING', 'UBYTE', 'UINT', 'ULONG', 'USHORT', '__doc__',
'__file__', '__name__', '__package__']
>>> c = pvaccess.Channel('int01')
>>> print c.get()
epics:nt/NTScalar:1.0
int value 0
>>> c.putInt(7)
>>> print c.get()
epics:nt/NTScalar:1.0
int value 7
>>> c.put(pvaccess.PvInt(5))
>>> print c.get()
epics:nt/NTScalar:1.0
int value 5
In the above, note that in addition to PV object classes like PvInt, one can also use standard Python types as arguments for channel puts.
- In a separate terminal, start the testDbPv IOC:
$ cd $EPICS4_DIR/pvaSrv/testTop/iocBoot/testDbPv
$ ../../bin/$EPICS_HOST_ARCH/testDbPv st.cmd- PV values can be changed using the IOC shell command
dbpf, e.g:
epics> dbpr 'float01'
ASG: DESC: DISA: 0 DISP: 0
DISV: 1 NAME: float01 SEVR: MAJOR STAT: LOLO
TPRO: 0 VAL: 0
epics> dbpf 'float01' 11.1
DBR_FLOAT: 11.1
- Monitor a channel in Python, passing in a subscriber object (function that processes PvObject instance):
>>> c = pvaccess.Channel('float01')
>>> def echo(x):
... print 'New PV value:', x
...
>>> c.subscribe('echo', echo)
>>> c.startMonitor()
>>> New PV value: epics:nt/NTScalar:1.0
float value 11.1
New PV value: epics:nt/NTScalar:1.0
float value 11.2
New PV value: epics:nt/NTScalar:1.0
float value 11.3
>>> c.stopMonitor()- In a separate terminal, start the v4 test RPC service:
$ cd $EPICS4_DIR/pvAccessCPP/bin/$EPICS_HOST_ARCH
$ ./rpcServiceExample # in terminal 2- RPC test channel is 'sum':
>>> rpc = pvaccess.RpcClient('sum')
>>> request = pvaccess.PvObject({'a': pvaccess.STRING, 'b': pvaccess.STRING})
>>> request.set({'a': '11', 'b': '22' })
>>> print request
structure
string a 11
string b 22
>>> response = rpc.invoke(request)
>>> print response
structure
double c 33- In a separate terminal, source the environment file and start python:
$ python # in terminal 2
>>> import pvaccess
>>> srv = pvaccess.RpcServer()
>>> def echo(x): # x is an instance of PvObject
... print 'Got object: ', x
... return x # service must return an instance of PvObject
>>> srv.registerService('echo', echo)
>>> srv.listen()
- In terminal 1, reuse previous request object
>>> rpc = pvaccess.RpcClient('echo')
>>> response = rpc.invoke(request)
>>> print response
structure
string a 11
string b 22- In terminal 2:
$ python
>>> import pvaccess
>>> srv = pvaccess.RpcServer()
>>> def sum(x):
... a = x.getInt('a')
... b = x.getInt('b')
... return pvaccess.PvInt(a+b)
>>> srv.registerService('sum', sum)
>>> srv.listen()
- In terminal 1:
>>> rpc = pvaccess.RpcClient('sum')
>>> request = pvaccess.PvObject({'a': pvaccess.INT, 'b': pvaccess.INT})
>>> request.set({'a': 11, 'b': 22})
>>> print request
structure
int a 11
int b 22
>>> response = rpc.invoke(request)
>>> print response
structure
int value 33- In terminal 2:
>>> import pvaccess
>>> srv = pvaccess.RpcServer()
>>> def hash(x):
... import hashlib
... md5 = hashlib.md5()
... md5.update(str(x))
... h = md5.hexdigest()
... dict = x.getStructureDict()
... dict['hash'] = pvaccess.STRING
... response = pvaccess.PvObject(dict)
... response.setString('hash', h)
... return response
>>> srv.registerService('hash', hash)
>>> srv.listen()- In terminal 1:
>>> rpc = pvaccess.RpcClient('hash')
>>> request = pvaccess.PvString('abcd')
>>> print rpc.invoke(request)
structure
string hash 0a380e7375d8c3f68d1bbe068141d6ce
string value