Re: What is causing C2? / USB autosuspension?

[Alan Jenkins <aj504-l9TVMAoMiWs2EctHIo1CcQ@public.gmane.org>]

Oliver Neukum wrote:
> Am Mittwoch 07 Mai 2008 00:24:58 schrieb Alan Jenkins:
>   
>> I think I've worked out how to avoid the lost key-presses.  Sometimes
>> they get lost; sometimes they don't.  The difference seems to how long I
>> wait after the keyboard suspends.  If I wait a few seconds after it's
>> suspended (as shown by the LEDs), then it resumes flawlessly.  It should
>> be possible to reduce the impact of the hardware misfeature by
>> increasing the timeout.  The longer the keyboard has been idle already,
>> the lower the probability it'll be used in the next few seconds. 
>>     
>
> This suggests a possible work around. Keyboards known to be buggy in this
> way could be reawoken periodically before the critical amount of time is over.
> How long is that time? What percentage of time does a keyboard need to be
> suspended for a positive energy balance?
>   
Sorry, I didn't explain that very clearly.

The problem happens if the keyboard resumes _immediately after_ it's 
autosuspended.  If I start typing as soon as the LED goes off, it loses 
some of the keypresses.  If I instead wait a few seconds before typing, 
it works flawlessly.  Since it's the keyboard that's resuming itself I 
don't think you could fix this.  Unless it's your code that's buggy and 
not the keyboard :-).

What I was trying to say was that I can mitigate this problem by 
increasing the autosuspend timeout from the default of 2 seconds.  I 
will quite often pause for periods of about 2 seconds while typing.  But 
if the keyboard is only suspended after 60 seconds of inactivity or 
longer, then it's far less likely that I will start typing immediately 
afterwards.

Alan