Re: [avrdude-dev] [bug #34339] back to back avrdude commands fail on dragon_isp on Ubuntu 10.10

[Xiaofan Chen]

On Thu, Dec 8, 2011 at 4:39 PM, Joerg Wunsch <address@hidden> wrote:
> As Xiaofan Chen wrote:
>
>> I think the root cause of the issue is the following codes
>> in usb_libusb.c.
>
>>   usb_reset(udev);
>
> No, it isn't.  The main reason is that all the Atmel-provided tools
> (JTAGICEmkII, AVRISPmkII, AVR Dragon) voluntarily leave and rejoin
> the USbus when we say "Good-bye" to them, causing them to be
> enumerated by the OS.  That "dead time" also applies to these tools on
> FreeBSD where AVRDUDE doesn't call usb_reset() by itself.

I see. In that case, what I said (data toggle issue) may not apply.

But why do this Atmel tools leave and rejoin the USB Bus is still
a mystery which is worth some time of investigations. Something
must trigger it to do that, right? And it will only be those commands
avrdude send to it.

Does this happen under Windows with the original Atmel driver
(Jungo) and libusb-win32 filter driver? Does it happen under Windows
with libusb-win32 device driver? What is the case with Mac OS X?

Does it make a difference using libusb-1.0+libusb-compat and
using legacy libusb-0.1, under Linux and Mac OS X?

BTW, Ubuntu/Debian are still using legacy libusb-0.1. But take note
libusb-0.1 is no longer maintained by the upstream libusb project.
Mac OS X will also be much better off using libusb-compat.

-- 
Xiaofan