Re: [libusb] Issue with Bulk Transfer in Raspberry PI

[Tim R. <ti...@pr...>]

Abhishek Madaan wrote:
>
> I have couple of other questions. Sometimes i get a following error
> from the libusb
>
> "warning [handle_timeout] async cancel failed -5 errno=22 "

Error -5 is LIBUSB_ERROR_NOT_FOUND.  This probably just indicates a
timing coincidence -- your timeout expired just as the request was
completed, so there was no request to cancel.


> Could you please explain why I am seeing this error.

It's not an error.  It's a warning.


> My second question with Cypress CyAPI.h i can use the SetXferSize to
> set the size of the transfer. When we used this in PC, we did see
> performance enhancement in fetching the image. Is there any way to set
> the SetXferSize in libusb?

You are already doing that.  The buffer you pass to
libusb_fill_bulk_transfer is the transfer size.  The Cypress library
happens to default to using many small transfers instead of one larger
transfer.  Earlier versions of Linux had a limitation on the size of a
single transfer.

Is your interface entirely synchronous?  That is, you must always sent a
vendor request before each frame is transferred?  There is no
"streaming" mode?  That reduces your performance, of course, but it also
means you don't really need to worry about queueing up multiple requests.

-- 
Tim Roberts, ti...@pr...
Providenza & Boekelheide, Inc.