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Message
From: Marc Reinig<mreinig@p...>
Date: Sat Feb 28 01:11:04 CET 2004
Subject: [usb] Enumeration
> Is there any difference if we send 18 bytes of data instead of 8 bytes
> when host requests for device descriptors after reset.
Yes. You only send what the host requests or less. If the host requests
less than 18 bytes, sending 18 bytes is an error.
> Can anybody explain what exactly is happening here
>
> host - > reset
> host -> request for device descriptors
> device -> responding with 18 bytes of device descriptor
> host -> reset
> device -> set address to 4
Up to this point, it is a valid sequence, including the 500 mSec wait
mentioned below.
> host -> reset
The most common reason for a reset following a set address is that you are
not listening on address 4 and the host gives up trying to talk to you and
resets you hoping your behavior will improve.
> Please note that acks are present but not mentioned. There is no nack
> either from device or host.
Do note that the host will NEVER NAK.
Marc Reinig
System Solutions
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