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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