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.
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. 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 On Thu, 2011-07-07 at 12:33 -0400, Phil Behnke wrote: > 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 > ------------------------------------------------------------------------------ > All of the data generated in your IT infrastructure is seriously valuable. > Why? It contains a definitive record of application performance, security > threats, fraudulent activity, and more. Splunk takes this data and makes > sense of it. IT sense. And common sense. > http://p.sf.net/sfu/splunk-d2d-c2 > _______________________________________________ Fx2lib-devel mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/fx2lib-devel ------------------------------------------------------------------------------ All of the data generated in your IT infrastructure is seriously valuable. Why? It contains a definitive record of application performance, security threats, fraudulent activity, and more. Splunk takes this data and makes sense of it. IT sense. And common sense. http://p.sf.net/sfu/splunk-d2d-c2 _______________________________________________ Fx2lib-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/fx2lib-devel
