Re: [Fx2lib-devel] Isochronous Streaming Using LibUSB from FPGA

[Xiaofan C. <xia...@gm...>]

On Fri, Jul 8, 2011 at 8:51 AM, Chris McClelland <fx...@m3...> wrote:
> FWIW, even with the FIFO flags clamped to endlessly source (or sink)
> data, I have never managed to get bulk reads (or writes) using LibUSB to
> give more than 25MiB/s on Linux and 18MiB/s on Windows.

Try libusb-1.0 under Linux and it may help since it support async
API (for all transfer types).

Under Windows, you can try to use libusb-1.0 Windows backend
but it does not support isoc transfer since it uses WinUSB.

On the other hand, libusb-win32 has its own async API and
supports isoc transfer.
http://sourceforge.net/apps/trac/libusb-win32/wiki/libusbwin32_documentation
http://sourceforge.net/apps/trac/libusb-win32/wiki/libusbwin32_examples

> Admittedly that is for bulk transfers which have more overheads than
> iso, and I have only tried the 0.1.x releases of LibUSB because they're
> API-compatible across Windows, MacOS and Linux.

libusb-1.0 API works under Windows, Mac OS X and Linux. The
problem is that 1.0.9 release keeps being delayed (first official
release to support Windows). But you can use libusb-pbatard.
http://www.libusb.org/
http://www.libusb.org/wiki/windows_backend


> The only other thing I can suggest is to compare the throughput you get
> with my firmware, host code and VHDL[1], but unless your FPGA board is a
> Digilent Nexys2, you will have to do some work on the pin constraints
> for your board. And remember this only deals with bulk, not iso.
>
> Sorry I can't be more helpful!
>
> Chris
>
> [1] http://www.makestuff.eu/wordpress/?page_id=1400


-- 
Xiaofan