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

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

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