Experimental Physics and
Industrial Control System

Simon Rose via Tech-talk <tech-talk at aps.anl.gov> · Wed, 10 May 2023 08:54:41 +0000

Hello S Banerian -

It looks to me like you are simply missing an import in python. Since you haven't shared the whole of your python code I can't tell, but you might be missing a 

from pvaccess import CA

at the top of your script. Note that according to your linked documentation there is such an object:

  >>> 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__']

See the third entry in the output of dir(pvaccess)

Cheers,

Simon

On 2023-05-10, 10:47, "Tech-talk on behalf of S Banerian via Tech-talk" <tech-talk-bounces at aps.anl.gov <mailto:tech-talk-bounces at aps.anl.gov> on behalf of tech-talk at aps.anl.gov <mailto:tech-talk at aps.anl.gov>> wrote:

I've set to work on upgrading some of our local EPICS infrastructure, and have (finally) installed Epics 7 on a couple of machines.

As part of that, we are trying out pvaccess PvaPy as an update to the pyepics that is currently used.

On a test system, i've been following the documentation [1,2] for PvaPy to monitor some pv's we track.

alas, we do not get the desired behaviour for monitoring CA PVs.

pvaChannel = Channel('enum01')
pvaChanne.isConnected()
pvaChannel.subscribe('echo', lambda x: print(f'{x}'))
pvaChannel.startMonitor()

(no errors encountered)

but when non-default is tried: 

ourPVchannel = pvaccess.Channel('int01',CA)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
NameError: name 'CA' is not defined

pvaccess.Channel('int01',providerType=CA)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
NameError: name 'CA' is not defined

suggestions as to what I can try next?

[1] https://github.com/epics-base/pvaPy <https://github.com/epics-base/pvaPy>
[2] https://epics.anl.gov/extensions/pvaPy/production/pvaccess.html#channel <https://epics.anl.gov/extensions/pvaPy/production/pvaccess.html#channel>

s banerian
UW Clinical Cyclotron

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System