[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 9:52 PM, Albert ARIBAUD <albert.aribaud at free.fr> wrote:
> Bonjour,
>
> Le Sun, 31 Jul 2016 20:51:51 +0100
> Luke Kenneth Casson Leighton <lkcl at lkcl.net> a écrit:
>
>> On Sun, Jul 31, 2016 at 8:34 PM, Albert ARIBAUD
>> <albert.aribaud at free.fr> wrote:
>>
>> > Thinking more about it, maybe you were thinking about up to 16 keys
>> > being depressed rather than 8, and the inputs' fan-ins adding up to
>> > twice more and the output's fan-out not being able to cope, leading
>> > to the input voltage not falling low enough for the keys to be
>> > detected as down.
>>
>>  not quite... maybe i was but hadn't quite got it through from
>> subconscious into words.. but that's a good point - i was thinking if
>> you used 8 fan-in and press 9 keys... if you have 16 fan-in and press
>> 9 keys...
>>
>>  basically the 16 fan-in it "activates" 50% less of the matrix.
>
> 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/

l.