[time-nuts] controlling instruments using USB

[Scott Stobbe]

In Windows, likely Mac/Linux with the NI visa library you get the IO trace
to help debug applications.

On Linux strace may give you some clues.

On Monday, 25 July 2016, jimlux <jimlux at earthlink.net> wrote:

> Semi-off-topic..
>
> I've got a bunch of Keysight/Agilent/HP instruments with USB interfaces
> that I want to control from Python.  On Mac and PC, the PyVisa library
> works great (either the one with the NI back end or the python only back
> end )
>
> But, on Ubuntu, there's no way to install the NI drivers (RH install only,
> and Ubuntu is debian..)
>
> So, I've been doing usbtmc, which sort of works.  (after figuring out all
> the udev rules stuff)
>
> If I do something like this from the python interpreter:
>
> >>> import usbtmc
> >>> myinst = usbtmc.Instrument( mfr, product)
> >>> myinst.write('some command')
>
> it works fine.
>
> But if I put the same three linesin a .py file and run it, it doesn't
> always work.. sometimes, you need to send the command twice.
>
> It seems it might be a timing thing (in libusb or usbtmc?) but putting
> some sleep() in between connecting to the instrument and doing the write
> doesn't seem to work all the time.
>
> Very curious.
>
> Any ideas?
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