geekhack Community > Keyboards
Rollover, where keyboard data might go, and ramble
Nonmouse:
--- Quote from: pex;2684 ---Well I'm just going to scrape up my membrane sheet and add diodes everywhere I can.
Unfortunately I know neither which type of diode (there are so many!) that I need nor do I know how (yet) I will be able to fit them in the little space provided by IBM/Lexmark.
--- End quote ---
Well, after taking a gander at the diodes in my Cherry G80-8113 board and wandering around the interwebs, I came up with either 1N914 or 1N4148 fast switching diodes. I then went and looked at the Keyboard Matrix Help page, and the author (Dave Dribin) has a section—"9. What Diode Parts to Use"— where he recommends either 1N4001 or 1N4148 diodes, with the 1N4148 having a much faster switching time (probably overkill fast).
I also found a place that has 1N4148 diodes at $1.00/100 pcs. Shipping's $7, but they've got all kinds of other cool junk (full-on geek candy store) that you could toss in to make the shipping worth it.
As far as fitting them in, they're a bit smaller than a grain of rice, with~ 1 cm leads (of course, you can clip them shorter), so fitting them in shouldn't be any problem at all. The easiest thing to do would probably be to solder them to the pins on the bottom of the circuit board, then scrape across the original circuit path with an exacto blade (if you don't break the old circuit, it'll just bypass the diode)
Oops. I just went and found a picture of the guts of a Model M board—the contacts are actually on a flexible sheet (looks like mylar) with the circuit runs printed on it. I'm sure there's got to be a way to insert diodes in the circuits. Anyone know anything about soldering leads to a mylar sheet, lol? Mebbe use conductive epoxy? I suppose if worse comes to worst, you could etch an actual circuit board for the bottom contact sheet, and solder the diodes to that. Hmmm... I've got a bunch of circuit board blanks kicking around, and some crappy membrane keyboards that could be donated for research. Maybe I'll put that on the list of hack projects. Would anyone be interested in an n-key rollover Model M? :D
Mikecase00:
--- Quote from: Nonmouse;2687 ---Would anyone be interested in an n-key rollover Model M? :D
--- End quote ---
What is the appeal of n-key rollover? In what scenario would you need to reliably press more than 8 keys at a time (which seems possible for my 1391401 through a PS/2 interface)? Eventually you start to run out of fingers to actuate keys with. Assuming you have an 84 key board triggering 8-key combinations, you have thousands of unique potential key combinations, certainly far more than would be practical to remember.
Nonmouse:
--- Quote from: Mikecase00;2689 ---What is the appeal of n-key rollover? In what scenario would you need to reliably press more than 8 keys at a time (which seems possible for my 1391401 through a PS/2 interface)? Eventually you start to run out of fingers to actuate keys with. Assuming you have an 84 key board triggering 8-key combinations, you have thousands of unique potential key combinations, certainly far more than would be practical to remember.
--- End quote ---
The biggest utility is for gamers. I'm not a huge gamer, but one of the games I do play, I have trouble with rollover on my notebook keyboard- I think the combination is qwa (I just checked with the rollover test page; this is the combination that doesn't work). A lot of games use closely clustered groups of keys for movement or firing or special actions for ease of play, but hitting several keys in the same row or column is the most likely scenario for dropping key presses. On my notebook keyboard, for instance, most combinations of three or keys in the same 2x2 block will only register 2, 1 or even 0 keys.
The n-key rollover is more about ensuring that no combinations of keys will ghost or mask than about making sure you can press 84 keys at once. (And, of course, there's the e-penis factor, too.)
xsphat:
--- Quote from: Nonmouse;2690 ---(And, of course, there's the e-penis factor, too.)
--- End quote ---
:)
I hate the minimum post length. I wish iMav would change it.
Mikecase00:
--- Quote from: Nonmouse;2690 ---The biggest utility is for gamers. I'm not a huge gamer, but one of the games I do play, I have trouble with rollover on my notebook keyboard- I think the combination is qwa (I just checked with the rollover test page; this is the combination that doesn't work). A lot of games use closely clustered groups of keys for movement or firing or special actions for ease of play, but hitting several keys in the same row or column is the most likely scenario for dropping key presses. On my notebook keyboard, for instance, most combinations of three or keys in the same 2x2 block will only register 2, 1 or even 0 keys.
The n-key rollover is more about ensuring that no combinations of keys will ghost or mask than about making sure you can press 84 keys at once. (And, of course, there's the e-penis factor, too.)
--- End quote ---
I'm not an avid gamer anymore, and I can't speak to your laptop or any other keyboard, but I've got to think that a PS/2 connected model M (with its 16 char buffer) would be more than sufficient. Plus, can't you re-map keys to work around the 2x2 block issue?
I think I read once that USB spec for keyboards is somehow more limited than PS/2 in the number of keys they can support pressed all at once. If that's the case, USB keyboards (of which most are these days) are poor choices for gaming because it's the interface that's the limiting factor. Upgrading the board with additional electronics isn't going to make the USB pipe any better. If your only connection option for a Model M is USB you'd be out of luck as well.
To have full n-key rollover support you need several things. Starting with the keyboard, it needs to register multiple key presses independently, not as blocks with other keys. The board needs an on-board char buffer to temporarily hold key press data until the computer is ready to receive it, not just dump the key presses to the interface as they come in. The keyboard to computer interface needs to accept and support transmit of multiple key presses simultaneously, and finally the OS software needs to be able to support n-key rollover.
Before I got out my soldering iron I'd adding things to the keyboard, I'd want to make sure everything downstream of my board can accept the additional key press data. Otherwise you'll end up with a kick-ass keyboard that performs exactly like the $5 Officemax special.
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version