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Logi Nu
m0rfar
Posts: 2
Registered: ‎11-28-2006

Simultaneous keypresses

Hi!

Are there specs for Logitech keyboards detailing how many keys can simultaneously be pressed somewhere? I know the gaming-keyboards tout alot of keys at the same time, but for the regular keyboards that doesn't take up half a desk..

Thanks!
Logi Nu
crizlax
Posts: 1
Registered: ‎11-29-2006

Re: Simultaneous key presses

[ Edited ]
normally the keys are stored in a buffer before being sent to the computer and the buffer is usually around 1mb.
presuming they are 8 bits in a byte and each key press is one byte i think the answer is more than you have on your keyboard but they still
have to be sent to the computer. a PS2 keyboard transfers data at 16khz which divided by 8 =2kbps. that is 2000 keys every second.
which should be far more than you have on your keyboard. USB (even the older versions) works much faster than this. and wireless connections should to.
so the answer is on a modern keyboard (past 5 years) all of them.

Message Edited by crizlax on 11-29-200612:33 PM

Logi Legend
rlowens
Posts: 6,594
Registered: ‎05-22-2006

Re: Simultaneous key presses

Very wrong. What ever gave you the idea keyboards would have a buffer any where as large as 1 MB?

Anyway, the issue is how many keys the keyboard can keep track of at once, not how fast it can send the data to the PC. A good "gaming" keyboard will use a microcontroller that can keep track of up to 10 keys at once. My Logitech S510 seems to be able to track up to 6 key states at once. You can use KeyScan to test your own keyboard.

Note that there also is the "key blocking" problem that comes from using a matrix to scan the keys instead of discrete addressing of each key on the keyboard (which would require as many data lines into the keyboard's microcontroller as there are keys on the keyboard). Note that you can't press all three keys of DFG at the same time for example. ExtremeTech has a good description of how this works.

-Richard L. Owens, author of the uberOptions mod for SetPoint. Unlock the options of your SetPoint-controlled device! mirror
Logi Nu
m0rfar
Posts: 2
Registered: ‎11-28-2006

Re: Simultaneous key presses

Right, thanks for the explanation :smileyhappy: I am still wondering though, if Logitech has published these specs somewhere, for normal keyboards, other than the bloated gaming keyboards that touts alot-of-keys-at-the-same-time specs.