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

[Phil B. <phi...@gm...>]

I think the sleep code is one of the problems, but if I lower or get rid of
it, libUSB starts to fail (in both python and C) with a LIBUSB_ERROR_IO
error.

On Fri, Jul 8, 2011 at 1:43 AM, Xiaofan Chen <xia...@gm...> wrote:

> On Fri, Jul 8, 2011 at 1:16 PM, Xiaofan Chen <xia...@gm...> wrote:
> > On Fri, Jul 8, 2011 at 12:26 PM, Phil Behnke <phi...@gm...>
> wrote:
> >> Xiaofan,
> >>
> >> Thanks for the help.  I'm using Linux with a 2.6.38.2 custom compiled
> >> kernel.  In addition to the python application, I wrote a basic C
> program to
> >> do the same thing, but I still have the same problem.  Both the
> >> python-libusb1 app and the C program are using async transfers.  The
> maximum
> >> isoc data rate of 24MBps should hopefully be enough, since my data from
> the
> >> FPGA is at 19MBps.  I've been experimenting with the data rate from the
> FPGA
> >> to the FX2; I can slow the data rate way down to ~6MBps and everything
> works
> >> great, but any faster than that and it starts to fail. :-/
> >
> > I see. It may not be that easy to achieve 24MB/s since your host side
> > code and the FPGA side logic need to be both good.
> >
> > I suggest you to post questions to libusb mailing list. I remember
> > there are reports there about sustaining this 24MB/s isoc transfer
> > and 35MB-45MB/s bulk transfer speed using FX2.
> >
>
> One quick test you can try. You might want to reduce the
> transfer buffer size, now it is 1024 * 500, which may be
> a bit too big. What if you reduce it to 1024 * 30? You
> are submitting 5 transfer simultaneously which is good.
>
>   transfer_object1=self.iso_xfer_object.fx2.getTransfer(500)
>
> transfer_object1.setIsochronous(endpoint=0x82,buffer_or_len=(1024*500),callback=self.createDataThread)
>
> And try to get rid of the sleep code.
>        #must sleep or LibUSB will start to fail
>        time.sleep(0.005)
>
> --
> Xiaofan
>
>
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