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From: Don Y <blockedofcourse@foo.invalid>
Newsgroups: sci.electronics.design
Subject: Re: Wake on USB event
Date: Fri, 31 Jan 2025 17:36:38 -0700
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On 1/31/2025 9:22 AM, Sylvia Else wrote:
>> It also seems like Windows only leaves USB ports powered up
>> during sleep *if* they were active while the machine was awake (?).
>
> It appears to me that the device drives a 'K' state onto the data lines for 
> between 1 and 15ms. The 'K' state is the opposite of the idle state.

Said another way, does the exchange contain "data" (a keystroke) or
is it purely for notification?

I.e., if the exchange *contained* a keystroke, then that would
suggest that I should see spurious keystrokes during normal
operation (?) -- which I don't.

> It's not necessarily the keyboard's fault - unplugging it prevents it from 
> waking the system up, if that's what it's doing, but it also means that it's 
> not plugged in. It could be the latter fact that makes the spurious wake-ups go 
> away.

Yes.  I rely on the keyboard to (eventually) wake the machine
/when I want to/ (accessing the power button is tedious).

> You could try plugging something else into that port instead.

I tried a different keyboard (same make/model -- all of my keyboards
are intentionally the same make/model).  This worked correctly.
Note the offending keyboard ALSO worked correctly -- until recently.

> Also plugging the keyboard in via a separate usb hub.
> 
> The results may hint at what to look at next.

The *right* way to do it, of course, would be to actually
look at the interface signals.  But, that's not particularly
convenient.  (Note to self:  build a USB breakout box)