VI_ERROR_LIBRARY_NFOUND Mac OS X 10.6.6

[aclewis182]

I am currently trying to use a NI GPIB-USB-HS coupled with pyVisa (Python) on my Macbook Pro running Snow Leopard.  I have not seen any posts with in the last year of people having issues with Snow Leopard, so I believe that I might be doing something wrong.

So far I have installed the latest version of NI VISA for OS X (version 5.0).  This produced zero errors.

I have installed pyVisa.  I am able to import modules from pyvisa, so I am fairly confident that it is alright.

I am able to import visa from pyVisa.  Doing dir(visa) gives the full list of modules available.

The errors come when I try to call the Instrument("GPIB::17") command.  It gives me a trace back with this error code being the last error: VI_ERROR_LIBRARY_NFOUND

The code I have used to produce this error is copied below.  Any help on this would be greatly appreciated!

--Adam

CODE SNIPPET:

from pyvisa.vpp43 import visa_library

visa_library.load_library("/Library/Frameworks/VISA.framework/Versions/A/VISA")

import visa

ps = visa.Instrument("GPIB::17")

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/aclewis/.envs/TIDE29/lib/python2.7/site-packages/PyVISA-1.3-py2.7.egg/pyvisa/visa.py", line 358, in __init__
    "lock")))
  File "/Users/aclewis/.envs/TIDE29/lib/python2.7/site-packages/PyVISA-1.3-py2.7.egg/pyvisa/visa.py", line 132, in __init__
    keyw.get("lock", VI_NO_LOCK))
  File "/Users/aclewis/.envs/TIDE29/lib/python2.7/site-packages/PyVISA-1.3-py2.7.egg/pyvisa/vpp43.py", line 753, in open
    byref(vi))
  File "/Users/aclewis/.envs/TIDE29/lib/python2.7/site-packages/PyVISA-1.3-py2.7.egg/pyvisa/vpp43.py", line 398, in check_status
    raise visa_exceptions.VisaIOError, status
pyvisa.visa_exceptions.VisaIOError: VI_ERROR_LIBRARY_NFOUND: A code library required by VISA could not be located or loaded.

[Jackie_B · Accepted solution]

Hi aclewis, 

Are you able to call GPIB in Measurement and Automation explorer? If you can find this out, we can narrow down if it is a problem with pyVisa or simply connecting to the device in general. Secondly, it seems that you are having the same problem as in this case: 

http://decibel.ni.com/content/docs/DOC-13584

Is this accurate? 

Some other resources that may help are as follows:

http://ubuntuforums.org/showpost.php?p=9059215&postcount=4

http://decibel.ni.com/content/docs/DOC-6742

Try to call this device without Python and see if this works. Good luck!

Regards,

Jackie

[aclewis182]

It turns out everything is working as expected.  The issue was not including the 0 in the device id.  Meaning that the call to "GPIB::17" should have been "GPIB0::17".  I found this by trial and error based on your recommendations.

Thanks for the help!