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Re: libusb future

by Xiaofan Chen :: Rate this Message:

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On Jan 3, 2008 7:47 AM, Tim Roberts <timr@...> wrote:

> Xiaofan Chen wrote:
> >
> > libusb-win32 0.1 has already implemented isochronous transfer and asynchronous
> >  I/O support.
> >
> > http://libusb-win32.svn.sourceforge.net/viewvc/libusb-win32/trunk/libusb1/src/dll/usb.h?view=markup
> >
> > int usb_isochronous_setup_async(usb_dev_handle *dev, void **context,
> >                                    unsigned char ep, int pktsize);
> > int usb_bulk_setup_async(usb_dev_handle *dev, void **context,
> >                            unsigned char ep);
> > int usb_interrupt_setup_async(usb_dev_handle *dev, void **context,
> >                                 unsigned char ep);
> >
> > int usb_submit_async(void *context, char *bytes, int size);
> > int usb_reap_async(void *context, int timeout);
> > int usb_reap_async_nocancel(void *context, int timeout);
> > int usb_cancel_async(void *context);
> > int usb_free_async(void **context);
> >
>
> That's an interesting approach.  The first three routines essentially
> create "pipe handles", so that a single routine can do all of the URB
> submission.
>
> Because of that, I think I would have used names more like
> "usb_create_pipe_handle".  After all, the "usb_xxx_setup_async" routines
> aren't really setting up a request.  And, of course, the last 5 APIs
> don't have any nouns, so it isn't clear what is being reaped, canceled,
> or freed.
>

To be honest, I do not quite understand isochronous transfer
(I was struggling to learn to write a host program to talk to
a bare-minimum isochronous transfer USB device in the
Microchip forum post) and asynchronous I/O works under
libusb-win32. I only know it is working since I tried out an example
(modified from the example given by Stephan Meyer).

http://www.nabble.com/Understanding-iIsochronous-transfer-with-libusb-win32-to11916957.html
http://forum.microchip.com/tm.aspx?m=270049&mpage=2

Part of the problem is my lack of knowledge, part of the
problem is the lack of documentation. Maybe you can look
into the codes to know how it works since you an an expert
for USB drivers under Windows.

Xiaofan

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