Re: [pyusb-users] Ubunto - No module named 'usb'

[Saeed M. <s.m...@gm...>]

Hi Xiaofan,

Thanks for your response and for sending me all the resources.

I have actually put my hand on every piece of information that I could get
from your github page and also other websites. libusb and pyusb have
been installed in the virtual environment but I can not import it. As I
mentioned before, I can import pyusb in the general directory, just not in
my virtual environment. Can you think of anything else?

Another thing is in regards to the write() method. When I try to send a
number, I have to put it in a list and the largest number I can send is 255
(1 byte). If I go beyond 255, I get this error:
*OverflowError: unsigned byte integer is greater than maximum*

But when I send the numbers as a string, for example '12345689', I can go
as big as I want without any errors as long as on the receiver side I have
set the number of bytes correctly in the read() method. Now, in my
application, I have to send a list of numbers via the USB port. A list that
contains between 9 to 35 numbers and each number is not going to take up
more than 2 bytes. I know that I can put the numbers in a loop, but is
there a way to send them all at once in number format, not string? Speed is
a critical element in my application and I have to avoid loops and
conversions at all costs.

Thanks,
Saeed



On Thu, Jan 14, 2021 at 4:54 PM Xiaofan Chen <xia...@gm...> wrote:

> On Thu, Jan 14, 2021 at 1:52 PM Xiaofan Chen <xia...@gm...> wrote:
> >
> > On Thu, Jan 14, 2021 at 1:44 PM Saeed Mirghasemi <s.m...@gm...>
> wrote:
> > > I have already done that and it does not work. Does anything else come
> to your mind?
> > >
> > > Also, where do I get a list of commands and their arguments in pysub?
> I am trying to
> > > set the baud rate and I do not know where to start.
> > >
> >
> > Obviously you need to install libusb as well. Please read the FAQ here.
> > https://github.com/pyusb/pyusb/blob/master/docs/faq.rst
> >
> > As for baud rate or things like that, that is not part of pyusb. You
> have to
> > understand the communication protocol of your USB device in order to
> > use libusb/pyusb.
> >
> > I suggest you read some basics of USB first.
> > http://www.usbmadesimple.co.uk/
> >
> > Then if you do not know the communication protocol, you have to reverse
> > engineering.
> > http://www.usbmadesimple.co.uk/
>
> Sorry the link is not correct.
>
> https://slomkowski.eu/tutorials/eavesdropping-usb-and-writing-driver-in-python/
>
> > And if your device is a standard USB class device like USB to Serial
> port,
> > then it is better not to use pyusb but rather pyserial.
> >
> > --
> > Xiaofan
>
>
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