Keyboard Rollover


rabidpoobear

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Hey guys,
I tried searching for this, and couldn't find anything, but it may be because of the term I used (am I the only one that refers to simultaneous keypresses as "rollover"?)

Anyway, the problem is this:
I have a Nokia E71x. It's a really fantastic phone, great battery life, WiFi, cheap, made of steel, etc. etc. and it has a full qwerty keyboard.
The problem is: it only has a 1-key rollover.

What does this mean? Well, a lot of people use membrane keyboards on desktops. These keyboards are designed with a sheet with circuitry underneath a set of keys. When you press down the keys, the rubber membrane contacts the circuitry and the keyboard can detect where your keypress was. However, because of the design of the circuit, when you hold down certain keys, then when you press another key it won't be detectable.

Most membrane keyboards have 2-key or 3-key rollover, so you can hold down any two keys and hit a 3rd key and it will detect. However with certain combinations you won't get any more than 3 keypresses before you start getting detection errors. I remember my brother used to use a 2-key rollover keyboard. Whenever we would play Counter-Strike, I could tell when he was walking, because you have to hold down Shift to walk, and he would try to walk diagonally (holding W and D keys) and his computer would "BEEP" at him.

So on my phone, this is a huge problem. The thing is, certain keys can't be detected when I have other keys pressed down. I know this sounds absurd and I wouldn't think it was possible if I hadn't experienced it myself, but on my phone, you literally can have detection errors of two simultaneous keys. For example, if I'm holding down the letter "t", the following keys cannot be detected: "r y f g h v b n m". Clever readers will notice that this a block of letters on the keyboard that is mapped to the number keys - R is 1, T is 2, Y is 3, etc. So I suspect this is a software problem rather than a hardware problem, because all keys outside of this block allow at least 2 simultaneous keypresses.

Now I can hear some of you saying "well, rabidpoobear, why is this a problem? why would we need to press multiple keys at once anyway?" This is a two-part answer. Firstly, when I type, I type "interleaved"; that is, I hit the second key before I've completely lifted off of the first key. I type reasonably quickly on desktop computers (a quick 1-minute test at typingtest.com -> 88 WPM, 100% accuracy) and so it frustrates me when I can't enter text very quickly. The reason I got a phone with a qwerty keypad was to speed up my typing from a regular 9-key phone. But I've found that the phone can't really keep up with my typing, because, for example, typing the word "try" will have a conflict between the t and the r and another between the r and the y, unless I consciously lift off each button before pressing the next. My crappy free phone from 5 years ago didn't have a problem with my method of typing, but a nice, new smartphone does?!

The second case where simultaneous keypresses are important are in games. For example, if you're using the d-pad to play a 2d game, wouldn't you want to be able to jump and run diagonally at the same time? or if you're using the keyboard, wouldn't you want to be able to strafe diagonally, crouch, and hop at the same time? (this actually occurs quite often when playing games such as Counter Strike.) And for this reason I use a mechanical keyboard on my desktop. It has infinite rollover of keys, but it's limited to a 6-key rollover because I don't install the drivers, and that's what the generic USB keyboard drivers are limited to. 6-key is plenty. Mechanical keyboards, for those not in the know, have an individual key switch under each key. It's a mechanical switch that, when pressing the keys down, you actually actuate a little switch inside of the keyswitch. So because there's a different hardware mechanism detecting each individual key, there's no problem with the circuitry intersections as in membrane keyboards.

<edit> remember the d-pad and the 4 buttons are part of the keyboard as well. or are they just part of the keymat?</edit>

So to get to my main question, does anyone yet know how the Pandora will handle key rollover? It looked to me like it uses a membrane keymat but I saw that it has keyboard contacts on the actual board - does that mean that it can sense each keypress individually or does it in essence behave the same as a membrane keyboard, just without a separate layer of circuitry (and the circuitry is just built into the board?)

I would probably have to cry for days and then eBay my pandora if it only had 1-key rollover like my phone. It's a really depressing fate to be relegated to, having to lift my fingers before pressing each subsequent key. If it has at least 2-key rollover, I'll be fine. If it has 3-key rollover or higher I'll have to hug it even more than before.
 

danielliu88888

i'm kind of hungry.
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you can press as many gaming controls as you want and the pandora will detect them all. for the keyboard however, i believe there will be only two key presses allowed at once (are you going to be pressing more than two when thumb typing?).
 

scrag_10

Still Fresh
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Sep 18, 2008
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I have come acorss this problem while playing frets on fire, but my key board also seems to seperate it into sections (hard to explain). Like my pinky and ring finger keys can't be held down at the same, or sumthang. time
 

lulzfish

Pandora Defense Squad
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My keyboard can detect 3 keys, unless two of them are on the same 'row' or something.

This works fine:
Left Alt
+ Up Arrow
+ Right Arrow

This does not work:
Left Alt
+ Up Arrow
+ Left Arrow

It seems that my Left Alt and Left Arrow keys collide. I ended up changing the nitrous in NFS to Left Control, and now I can turn left while using nitrous.
 

r00tw00t

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Also had this problem when playing CS. But I'm not worried because I don't think I'll never play an FPS game using the Pandora-keyboard [WASD]. And for typing I will use my two ( :) ) thumbs
 

WizardStan

Mega GP Mania
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May 24, 2008
Messages
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The worst part is when the keyboard matrix registers a button press, but then you press another key which is fine, but then release the first key which it fails to recognize. I tried to abuse that particular feature as a kind of auto run, but it never worked out as intended.
 
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