[Fx2lib-devel] Isochronous Streaming Using LibUSB from FPGA

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

Hi All,

I've been have a issue streaming data from an FPGA to a PC using the FX2LP
and LibUSB.  The FPGA is sending 8 bits to the FX2 at a rate of 20MHz (152
Mbps) using isochronous mode.  The problem I'm having is that I cannot get
data from the FX2's buffer to the PC fast enough and the buffer becomes
full, causing me to miss some data.  I'm not sure where the bottle neck is.
The FX2 is set to iso mode, with 1024 bytes per packet, and 3 packets per
microframe, so I should have enough bandwidth to empty the buffer.  I'm
attached my firmware (fpga.c), descriptor file, and libusb driver.  The
driver was written in Python using python-libusb1 wrappers.  I have a LED on
the FPGA board which will read the FULL flag on the FX2 and light an LED
when full.  By inspection, it looks like the LED is lit at about 50% duty
cycle.  I've been working on this for quite a while and would really
appreciate any tips.

Thanks!

Best Regards,
Phil Behnke