Thanks for the info :-)
Regards!
Alan
Date: Mon, 15 Apr 2013 10:21:51 +0200
From: thempe...@gmail.com
To: pyusb-users@lists.sourceforge.net
Subject: Re: [pyusb-users] Read speed improvement.
Dear Alan,
For Full Speed device you will probably not see any difference (maybe on very
slow machine).
This makes only difference for fast transfers and large data packages.
For me it makes a difference when transfer rate is >5MB/s.
Best Regards,
Tomek
On Sun, Apr 14, 2013 at 12:18 AM, Alan Jhonn Aguiar Schwyn
<alan...@hotmail.com> wrote:
> From: wander.lair...@gmail.com
> Date: Sat, 13 Apr 2013 11:50:08 -0300
> To: pyusb-users@lists.sourceforge.net
> Subject: Re: [pyusb-users] Read speed improvement.
>
> 2013/4/2 Tomasz Hemperek <thempe...@gmail.com>:
> >
> > Dear All,
> >
> > I am not sure if i should open a ticket so I am writing here.
> > Remark: I am very new to python (1 week).
> >
> > I found that small change improves max read transfer speed.
> > In my case from ~5MB/s to ~15MB/s (~15MB/s is the limit for this device).
> >
> > The problem is in initialization of _interop.as_arrary
> >
> > Example in libusb1.py in __read function the memory is allocated this way:
> > data = _interop.as_array((0,) * size)
> > this creates a tuple of size and then an array.
> >
> > If you change initialization to
> > data = _interop.as_array( '\x00' * size )
> > makes it much faster.
> >
> > Example speed test: http://dl.dropbox.com/u/2937630/code/array_init_test.py
> >
> > For write - core.write could recognize if it receives type==array.array ant
> > not to reinitialize memory.
> >
>
> Sorry for the long delay in answering your question. Would you mind
> opening a ticket in github?
Good!But in "normal" calls I don't get much improve.. Send 5 bytes to a device
(PIC18F4550) and read 5 takes 0,0019843.. seconds
in average.I use "bulk" write and read. This time is "normal" or the problem
would befirmware of the PIC?
Regards!
Alan
The code:http://sourceforge.net/p/butia/code/ci/master/tree/pybot/
> --
> Best Regards,
> Wander Lairson Costa
>
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