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Discussion Groups | Comp.Arch.Embedded | USB Bus Reset - General Query on USB

There are 3 messages in this thread.

You are currently looking at messages 0 to 3.

USB Bus Reset - General Query on USB - Sandeeptssmg - 2009-10-29 07:21:00

Hi All,
  my first query on this excellent site :-). Am currently looking for some
info on USB reset. In a USB enumeration failure scenario, could you please
let me know how many times does the hub driver sends a RESET to the device
before it recognizes that USB cannot be enumerated and pops up a msg "USB
device unrecognized". 

I presume its 3 times before the host driver can pop the error msg on the
screen. Does it vary based on different host controllers or is it a
standard ? Please provide if any pointers ?

Regards,
Sandeep 

	   
					
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Re: USB Bus Reset - General Query on USB - Arlet - 2009-10-29 16:37:00

On Thu, 29 Oct 2009 06:21:52 -0500, Sandeeptssmg wrote:

> Hi All,
>   my first query on this excellent site :-). Am currently looking for some
> info on USB reset. In a USB enumeration failure scenario, could you please
> let me know how many times does the hub driver sends a RESET to the device
> before it recognizes that USB cannot be enumerated and pops up a msg "USB
> device unrecognized". 
> 
> I presume its 3 times before the host driver can pop the error msg on the
> screen. Does it vary based on different host controllers or is it a
> standard ? Please provide if any pointers ?

The host must retire a transfer after 3 errors, according to the
2.0 standard. See section 10.2.6. It doesn't say anything about sending
another RESET.

http://www.usb.org/developers/docs/

Re: USB Bus Reset - General Query on USB - =?iso-8859-1?Q?Leo_Havm=F8ller?= - 2009-10-30 00:55:00

"Sandeeptssmg" <s...@gmail.com> wrote in message 
news:n...@giganews.com...
> Hi All,
>  my first query on this excellent site :-). Am currently looking for some
> info on USB reset. In a USB enumeration failure scenario, could you please
> let me know how many times does the hub driver sends a RESET to the device
> before it recognizes that USB cannot be enumerated and pops up a msg "USB
> device unrecognized".
>
> I presume its 3 times before the host driver can pop the error msg on the
> screen. Does it vary based on different host controllers or is it a
> standard ? Please provide if any pointers ?

It depends on the host OS. Windows, Mac, Linux and other unix'es have 
(small) differences in enumeration.
But if your device can pass usbcv tests you are on the right track.

Leo Havmøller.