4 ms·
Keyboard Ghosting
- eosrei 12y agoMost mechanical keyboards have N-Key Rollover or Anti-Ghosting to handle the situation of multiple simultaneous key-presses. USB supports up to ten keys, while only PS/2 has full N-Key Rollover support. Here's a good explanation of the issue with an interactive typing test showing the issue: http://blog.controlspace.org/2010/08/n-key-rollover-what-it-is-and-how-to.html http://blog.controlspace.org/2010/08/n-key-rollover-what-it-...
- Freaky 12y agoUSB keyboards can get around the ten key limitation by presenting themselves as multiple devices.
- 0xD000000D 12y agoOr by using a passive USB to PS/2 adapter. USB and PS/2 are both serial protocols with similar wiring, so a USB keyboard that supports passive adapters can detect what kind of port it is plugged into when powered on, then send unmodified PS/2 through the USB cable. For this reason, there are a few mechanical keyboards that only support N-key rollover in PS/2 mode, dropping down to 10-key rollover in USB-HID mode (it's cheaper and less likely to cause bugs than presenting as multiple HIDs, and anyone that cares about N-key rollover probably has a PS/2 port anyway).
- buckbova 12y agoFYI, this was posted a couple times before and once with some discussion associated. https://news.ycombinator.com/item?id=7358333 https://news.ycombinator.com/item?id=7358333
- matmann2001 12y agoThey never actually say what they do.
- falcolas 12y agoTo counter ghosting over USB? They use a different protocol than the HID keyboard protocol. If you're not constrained by that protocol, you can send as many key combinations as your keyboard is capable of generating. Of course, this means that you need custom keyboard drivers, either installed via a package or by default, and the keyboard needs to be capable of switching protocols, based on if its talking to a OS with compatible drivers or a BIOS without.
- njharman 12y agoSince the Microsoft Mouse I've always thought MS a better hardware company than software one.
- zupa-hu 12y agoHow odd I have a MS mouse and I thought, hmm, if their mouse is so good I'm going to try their keyboard.
- zupa-hu 12y agoAnyone knows about such keyboard but in smaller size, as in whatever those left column keys are? Also this looks like an "amazing artwork" I just want a damn keyboard that is small, works and looks boring.
- Zuikaku 12y agoTake a look at either the Vortex Poker (POK3R as the current iteration) or the Atomic/Planck.
- zupa-hu 12y agoThx a lot Zuikaku! Hahaha, that's minimal :) Will check it out more later.
- zupa-hu 12y agoI totally fall in love with Pok3r, thx again for the reference! Funnily the main reason I was interested in that anti-ghosting was that I have a keyboard rewriting script that maps the CAPS to be a function key, I'm using IJKL as arrows for example. And now I have to realize I'm not the first person who thought about that. Pok3r ships with that by default.. Really?! I feel like in wonderland... :D
- x0054 12y agoHmm, on rMBP the S-D-C combo does not work, who would have thunk it, never wondered about this. Educational :)
- TheLoneWolfling 12y agoI never got why keyboards don't just use a demux / output selector. Tie each switch through a diode, toggle one column to high, read the rows. Repeat, scanning through all columns. But then again, it's kind of pointless, what with USB limitations (!) and all.
- bandrami 12y agoBecause of historical expectations about the semantics of the "Escape" key, IIRC.
- TheLoneWolfling 12y agoElaborate?
- deleted 12y ago[deleted]