[Arm-netbook] EOMA-68 laptop Keyboard support improvement pushed

[Luke Kenneth Casson Leighton]

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crowd-funded eco-conscious hardware: https://www.crowdsupply.com/eoma68


On Sun, Jul 31, 2016 at 11:02 PM, Albert ARIBAUD <albert.aribaud at free.fr> wrote:
> Le Sun, 31 Jul 2016 21:56:13 +0100
> Luke Kenneth Casson Leighton <lkcl at lkcl.net> a écrit:
>
>> > Hmm... Not getting what you're hinting at. Can you develop?
>>
>>  it's related to mis-detection of keys.  if you press certain
>> combinations in certain ways, you get "ghost" keys that you can't tell
>> if they were actually pressed or not.  by reducing the number of keys
>> that are "live" (16 fan-in only activates up to 8 maximum where as 8
>> fan-in could activate up to 16 maximum) you reduce the possibility of
>> "ghosting".
>>
>>  there was an article online about it... ah!  found it:
>> http://pcbheaven.com/wikipages/How_Key_Matrices_Works/
>
> Ok, got your point now.
>
> Too late today to do probabilities (heck, even in the morning right
> after my coffee shot I would not trust my skills in probabilities).
> Still, I intuitively (yeah, I know) think there is no reduction in the
> risk of ghosting when transposing the matrix, because there is no
> asymmetry in the ghosting problem; ghosting occurs as soon as three of
> the four connections between two rows and two columns are closed: at
> that point, there is no way to tell whether the fourth connection is
> open or closed, and this, regardless of any notion of "row", "column",
> or "activity".
>
> IOW, whether or not a given state of the keyboard matrix will exhibit
> ghosting is only defined by the distribution of the depressed keys on
> the matrix, not by the rotation with which we look at that matrix or
> whether it currently has an active column.

 my point is: if you've activated 2x the amount of keys because you're
firing on "rows" (16 activated) instead of "columns (only 8
activated), there's now 2x the chance of having a "ghosting" problem.

 i think.

 too much for my brain to cope with....