USB Bus Reset - General Query on USB

Oct 29, 2009 2 Replies

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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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.

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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.

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