{"id":1245,"date":"2012-07-13T16:34:03","date_gmt":"2012-07-13T21:34:03","guid":{"rendered":"http:\/\/bardagjy.com\/?p=1245"},"modified":"2013-04-14T20:28:54","modified_gmt":"2013-04-15T01:28:54","slug":"pyvisa-on-osx","status":"publish","type":"post","link":"https:\/\/bardagjy.com\/?p=1245","title":{"rendered":"PyVISA on OSX"},"content":{"rendered":"

So after some persistance, I’ve managed to get PyVISA<\/a> working under OS X 10.6.8 Snow Leopard on a late 2008 MacBook Pro. <\/p>\n

    \n
  1. Download and install NI VISA 5.1.2 for OSX<\/a><\/li>\n
  2. In your home directory, create the file .pyvisarc<\/code> with the contents
    \n[Paths]
    \nVISA library: \/Library\/Frameworks\/VISA.framework\/VISA<\/code><\/li>\n
  3. Download and untar PyVISA 1.4<\/a><\/li>\n
  4. Install as root with easy_install<\/code>
    \n$ sudo easy_install PyVISA-1.4<\/code><\/li>\n<\/ol>\n

    Now, NI VISA 5.1.2 was compiled for 32 bit systems – check this with:
    \n$ file \/Library\/Frameworks\/VISA.framework\/VISA<\/code><\/p>\n

    If it returns i386, not x86_64, you’ve got a 32 bit binary. If you try to use PyVISA as shipped with OSX, it will default to 64 bit mode. When you try to import visa<\/code>, you’ll get several errors reading no suitable image found<\/code> and no matching architecture in universal wrapper<\/code>. <\/p>\n

    This is a CTYPES problem and discussed in this stackoverflow<\/a> question.<\/p>\n

    It is possible to force OSX to run Python in 32 bit mode by
    \n$ export VERSIONER_PYTHON_PREFER_32_BIT=yes<\/code><\/p>\n

    Which you could put in your .profile<\/code> or .bashrc<\/code> to run every time you open a new shell. But I didn’t want to default to 32 bit python, I’d rather force it into 32 bit mode when needed. <\/p>\n

    So, to my .profile<\/code> I added
    \nalias python386='arch -i386 python'<\/code><\/p>\n

    To force a script to execute under 32 bit Python, rather than including the line #!\/usr\/bin\/python<\/code>, I start my script with #!\/usr\/bin\/env arch -i386 python<\/code>.<\/p>\n

    I’m still working on a way to force iPython to run in 32 bit mode, if started with arch<\/code> it still calls system python<\/code>. Most unfortunately, I do not have 32 bit versions of many useful packages (e.g., numpy<\/code> and pylab<\/code>) forcing me to save data (say as a CSV file) and process it with 64 bit Python). That will become really tiresome if I try to be interactive with a PyVISA.<\/p>\n

    I specified the version numbers that I used, but am unsure if they are required, just what worked for me.<\/p>\n

    Below, I’ve included a short demo, verifying proper operation of the HP\/Agilent 34401A.<\/p>\n

    \r\n#!\/usr\/bin\/env arch -i386 python\r\n# pyvisa calls NI visa which is compiled with 32 bits, so run python in 32 bit\r\nfrom visa import *\r\n\r\ninst = SerialInstrument('ASRL1',\r\n                        baud_rate = 9600,\r\n                        data_bits = 7,\r\n                        stop_bits = 2,\r\n                        parity = even_parity,\r\n                        term_chars = CR+LF,\r\n                        end_input = term_chars_end_input,\r\n                        send_end = True,\r\n                        delay = 2\r\n                        )\r\n\r\ninst.write('SYST:REM')\r\ninst.write('*RST')\r\nsleep(10)\r\ninst.write('SYST:REM')\r\nprint inst.ask('*IDN?')\r\n<\/pre>\n
    It should print HEWLETT-PACKARD,34401A,0,11-5-2<\/code>, or whatever your software version is.<\/p>\n","protected":false},"excerpt":{"rendered":"
    So after some persistance, I’ve managed to get PyVISA working under OS X 10.6.8 Snow Leopard on a late 2008 MacBook Pro. Download and install NI VISA 5.1.2 for OSX In your home directory, create the file .pyvisarc with the contents [Paths] VISA library: \/Library\/Frameworks\/VISA.framework\/VISA Download and untar PyVISA 1.4 Install as root with easy_install […]<\/p>\n","protected":false},"author":1,"featured_media":1267,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"ngg_post_thumbnail":0,"footnotes":""},"categories":[19],"tags":[99,75,74,100,98],"_links":{"self":[{"href":"https:\/\/bardagjy.com\/index.php?rest_route=\/wp\/v2\/posts\/1245"}],"collection":[{"href":"https:\/\/bardagjy.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/bardagjy.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/bardagjy.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/bardagjy.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=1245"}],"version-history":[{"count":25,"href":"https:\/\/bardagjy.com\/index.php?rest_route=\/wp\/v2\/posts\/1245\/revisions"}],"predecessor-version":[{"id":1352,"href":"https:\/\/bardagjy.com\/index.php?rest_route=\/wp\/v2\/posts\/1245\/revisions\/1352"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/bardagjy.com\/index.php?rest_route=\/wp\/v2\/media\/1267"}],"wp:attachment":[{"href":"https:\/\/bardagjy.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1245"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/bardagjy.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1245"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/bardagjy.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1245"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}