Mailing List Archive

On Sat, 5 May 2012, Paolo Iommarini wrote:

> I have a problem when three keys are pressed (I have the english keyboard).
> There are some keys combination that generates an additional key press.
> This seems a system bug.
>
> It can be reproduced in any textbox (like the contact search).
> If you press a+x+up arrow you'll see a "p".
>
> I noticed it while using the Game Gripper with the psx emulator: pressing
> down+left+circle will end in a down+left+triangle+circle combination.
> I debugged the key-press-event and it is really getting a press event for the
> key "p" (code 33).
>
> There are also other strange keys combination like
> a+x+return = ","
> a+x+. = "o."
>
> Can someone please test it and say if it's really a system bug?

This is a hardware issue. And there are more combinations revealing this
issue. See for example here:

http://talk.maemo.org/archive/index.php/t-40806.html

I believe it is possible to recognize the fake key press/release events
by analyzing the timing of those events, thus discarding these events
and working around the hardware problem. But to my knowledge, noone has
done it yet, and I do not expect anyone to actually do it.

--
Matan Ziv-Av. matan@svgalib.org


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I thought it might be an hardware issue...
Too bad, I'll try to find a workaround.

Many thanks

> On Sat, 5 May 2012, Paolo Iommarini wrote:
>
>> I have a problem when three keys are pressed (I have the english
>> keyboard).
>> There are some keys combination that generates an additional key press.
>> This seems a system bug.
>>
>> It can be reproduced in any textbox (like the contact search).
>> If you press a+x+up arrow you'll see a "p".
>>
>> I noticed it while using the Game Gripper with the psx emulator:
>> pressing down+left+circle will end in a down+left+triangle+circle
>> combination.
>> I debugged the key-press-event and it is really getting a press event
>> for the key "p" (code 33).
>>
>> There are also other strange keys combination like
>> a+x+return = ","
>> a+x+. = "o."
>>
>> Can someone please test it and say if it's really a system bug?
>
> This is a hardware issue. And there are more combinations revealing this
> issue. See for example here:
>
> http://talk.maemo.org/archive/index.php/t-40806.html
>
> I believe it is possible to recognize the fake key press/release events
> by analyzing the timing of those events, thus discarding these events
> and working around the hardware problem. But to my knowledge, noone has
> done it yet, and I do not expect anyone to actually do it.
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On Saturday, May 05, 2012, Paolo wrote:

> I thought it might be an hardware issue...

That is a phenomon called ghost-key. This is something inherent in matrix-keyboards.

http://www.dribin.org/dave/keyboard/one_html/

> Too bad, I'll try to find a workaround.

The only workaround is to suppress the 3'rd key (which will appear as two new keys) if the pressed keys form a rectangle in the keyboard matrix.
________________________________________
From: maemo-developers-bounces@maemo.org [maemo-developers-bounces@maemo.org] on behalf of ext Paolo Iommarini [sakya_tg@yahoo.it]
Sent: Saturday, May 05, 2012 9:08 PM
To: maemo-developers
Subject: Re: Problem with three keys pressed

I thought it might be an hardware issue...
Too bad, I'll try to find a workaround.

Many thanks

> On Sat, 5 May 2012, Paolo Iommarini wrote:
>
>> I have a problem when three keys are pressed (I have the english
>> keyboard).
>> There are some keys combination that generates an additional key press.
>> This seems a system bug.
>>
>> It can be reproduced in any textbox (like the contact search).
>> If you press a+x+up arrow you'll see a "p".
>>
>> I noticed it while using the Game Gripper with the psx emulator:
>> pressing down+left+circle will end in a down+left+triangle+circle
>> combination.
>> I debugged the key-press-event and it is really getting a press event
>> for the key "p" (code 33).
>>
>> There are also other strange keys combination like
>> a+x+return = ","
>> a+x+. = "o."
>>
>> Can someone please test it and say if it's really a system bug?
>
> This is a hardware issue. And there are more combinations revealing this
> issue. See for example here:
>
> http://talk.maemo.org/archive/index.php/t-40806.html
>
> I believe it is possible to recognize the fake key press/release events
> by analyzing the timing of those events, thus discarding these events
> and working around the hardware problem. But to my knowledge, noone has
> done it yet, and I do not expect anyone to actually do it.
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> The only workaround is to suppress the 3'rd key (which will appear as
> two new keys) if the pressed keys form a rectangle in the keyboard
> matrix.
I tried but it's really not easy (maybe impossible).
If the three keys are pressed simultaneously the order of the key press
event is "random".

Also in the case of a+x+up arrow I get a sequence of:
Key: 111 Pressed time 1175712370
Key: 33 Pressed time 1175712398
Key: 38 Pressed time 1175712398
Key: 53 Pressed time 1175712398

But if I press a+x+p (which is the ghost key I get using the previous
sequence) I get:
Key: 38 Pressed time 1175773269
Key: 53 Pressed time 1175773269
Key: 33 Pressed time 1175773284
Key: 111 Pressed time 1175773284

The key with code 33 (the p) is always fired before the 111 (up arrow) so
there's no way I can say if the user really pressed the p or the up arrow.
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On Saturday, May 06, 2012, Paolo wrote:

> > The only workaround is to suppress the 3'rd key (which will appear as
> > two new keys) if the pressed keys form a rectangle in the keyboard
> > matrix.
> I tried but it's really not easy (maybe impossible).

There is only one way to "fix" the ghost key problem - that is to suppress all *new* key events that are part of a ghost key "rectangle".

> Also in the case of a+x+up arrow I get a sequence of:
> Key: 111 Pressed time 1175712370

Key event 111 send

> Key: 33 Pressed time 1175712398
> Key: 38 Pressed time 1175712398
> Key: 53 Pressed time 1175712398

Suppress all.

> But if I press a+x+p (which is the ghost key I get using the previous
> sequence) I get:
> Key: 38 Pressed time 1175773269
> Key: 53 Pressed time 1175773269'

Key event 38 and 53 send

> Key: 33 Pressed time 1175773284
> Key: 111 Pressed time 1175773284

Both suppressed


> The key with code 33 (the p) is always fired before the 111 (up arrow) so
> there's no way I can say if the user really pressed the p or the up arrow.

No that is the point - from the HW point of view there is no way to see which
one is really pressed.

The only thing you can do is to hide the problem.


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see http://wiki.maemo.org/N900_Hardware_Subsystems#Keyboard where I elaborated
about the problem, though only regarding qualifier keys (Fn, Shift, Ctrl)

/j
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