USB Bulk Transfer Speeds

[raxpeter]

Hello folks,

I hv been playing around with the Startkit, trying to utilize the USB interface for sending data to and from Startkit. I managed to get the Custom Bulk Transfer code running on Startkit, using the Dynamic Loading method and perform Host-PC speed benchmarks. I am getting around 3.6 MBps using the provided Bulktest application, and found mentioned in Xmos documentation that speed range would typically vary between 1 to 10 MBps.

I have had USB 2.0 chipsets transferring above 30MBps. I am wondering whether this above mentioned limit is due to hardware limitation or some implementation issues.

I am looking into using Asynchronous IO using Libusb-1.0. I would love if someone can clarify if its a path worth experimenting.

Regards,

Rakesh

[segher]

What host OS are you using? Any hubs in the chain?

The xcore/XUD side of things doesn't limit things much
(if at all). The above factors matter a lot though; and yes,
if properly used async helps (again dependent on host OS);
what also helps is doing bigger transfers on the host side.

[Ross]

I got half way though updating the bulk-test demo for the async libusb API in my spare time but have not finished it yet - if you would like to help I can put it on a branch on github.

[raxpeter]

segher: just to be inline - i tried on both windows and linux... no hubs - direct to port.
i'll try out the big writes as you suggested sometime now..

ross: it'd be great if u can git the code.. i'll try and add to it... btw, just curious - what speeds did you get with synchronous bulk-test ?

[Ross]

ross: it'd be great if u can git the code.. i'll try and add to it... btw, just curious - what speeds did you get with synchronous bulk-test ?

Similar speeds to you on my MacBook from memory - its very host limited.

[asid61]

Would you be able to tell me exactly how you got USB transfer working?