On Thu, 25 Sep 2014, Robert Wessel wrote:> The problem is in some ways analogous to keyboards without n-key > rollover. A simple scannable array of switches (keys) can easily (and > cheaply!) detect a switch closure (key press), but if you press two > keys at once, it gets confused. Fortunately you don't see that on > real keyboards anymore (the last time I saw a non-n-key-rollover > keyboard was probably about 1980, before then it was actually an > advertised feature), but you do still see the effects on many > (particularly inexpensive) calculators (where it's even worse, since > keyboard scanning is usually tied to the LCD refresh, so when you > press several keys at once, you mess up the display as well).[more OT] Have to disappoint you, but almost all keyboards today are not N-key rollover. The reason - using cheap membrane or rubber domes for contact. Currently there is some kind of a "revival" trend going on (particularly fueled by gamers?), so there are few modern keyboards using microswitches+diodes or capacitive sensing, but the mass market is still 2-KRO.
OT: Hackintosh
Started by ●September 23, 2014
Reply by ●September 25, 20142014-09-25
Reply by ●September 25, 20142014-09-25
On 9/25/2014 12:50 PM, Theo Markettos wrote:> In comp.arch.embedded Don Y <this@is.not.me.com> wrote: >> Good point. AFAICT, one of my laptops has seen some attention on this >> front. Just not sure I'd want to scrub the laptop just to "play". > > This may be of interest: > http://wiki.osx86project.org/wiki/index.php/Apple_hardware > (if slightly out of date) > There's plenty more info on that site.Yeah, this seems to be a more effective way of approaching the problem (feasability). The other sites I've seen seem to be more along the line of "I got it to work on a __________". Far too many potential "___________" for me to hope for a "hit"!>> OTOH, if my colleague fails to "come through" for me, it seems like it >> would be the least troublesome way to proceed... > > One of your Atom boards might be a useful target, depending on the spec, > though probably only for Snow Leopard or earlier. It was particularly > popular on Atom netbooks.The video on my Atom SBC is, AFAICT, SiS-based. So, no joy there. I've received another offer from another (out-of-state) friend. But, that gets more tedious to exploit (shipping, risk of damage in transit, etc.) I can also put this on my list of things to watch for at the various "surplus" outlets that I frequent: borrow one and return it... no "loss" there!
Reply by ●September 25, 20142014-09-25
On Thu, 25 Sep 2014 23:41:21 +0300, Vladimir Ivanov <none@none.tld> wrote:> >On Thu, 25 Sep 2014, Robert Wessel wrote: > >> The problem is in some ways analogous to keyboards without n-key >> rollover. A simple scannable array of switches (keys) can easily (and >> cheaply!) detect a switch closure (key press), but if you press two >> keys at once, it gets confused. Fortunately you don't see that on >> real keyboards anymore (the last time I saw a non-n-key-rollover >> keyboard was probably about 1980, before then it was actually an >> advertised feature), but you do still see the effects on many >> (particularly inexpensive) calculators (where it's even worse, since >> keyboard scanning is usually tied to the LCD refresh, so when you >> press several keys at once, you mess up the display as well). > >[more OT] > >Have to disappoint you, but almost all keyboards today are not N-key >rollover. The reason - using cheap membrane or rubber domes for contact. > >Currently there is some kind of a "revival" trend going on (particularly >fueled by gamers?), so there are few modern keyboards using >microswitches+diodes or capacitive sensing, but the mass market is still >2-KRO.I dispute that. PC keyboards report key down and key up to the mainboard for all keys. That intrinsically gives them n-key rollover. Whether or not it is processed that way is another matter, that is not done on the keyboard. ?-)
Reply by ●September 25, 20142014-09-25
In comp.arch.embedded josephkk <joseph_barrett@sbcglobal.net> wrote: (snip)> I dispute that. PC keyboards report key down and key up to the mainboard > for all keys. That intrinsically gives them n-key rollover. Whether or > not it is processed that way is another matter, that is not done on the > keyboard.That means that they have the ability to report such keys, not that they actually do it. The do have to report shift, control, alt, and such, in addition to other keys that are pressed while some combination of those is down. To do a proper N-key rollover, you need a diode in series with each key switch. Without the diodes, you can get a large combination of more than 2 keys, but not all of them. -- glen
Reply by ●September 26, 20142014-09-26
On Fri, 26 Sep 2014, glen herrmannsfeldt wrote:> In comp.arch.embedded josephkk <joseph_barrett@sbcglobal.net> wrote: > > (snip) > >> I dispute that. PC keyboards report key down and key up to the mainboard >> for all keys. That intrinsically gives them n-key rollover. Whether or >> not it is processed that way is another matter, that is not done on the >> keyboard. > > That means that they have the ability to report such keys, not > that they actually do it. > > The do have to report shift, control, alt, and such, in addition > to other keys that are pressed while some combination of those > is down. > > To do a proper N-key rollover, you need a diode in series with > each key switch. Without the diodes, you can get a large > combination of more than 2 keys, but not all of them.Indeed. For a matrix keyboard relying on electrical contact, the lack of diodes leads to 2-KRO. Optimized layouts, like placing modifiers on carefully selected rows/columns, might somewhat hide this. Heck, even the classic IBM M keyboards, being membrane, are 2-KRO. Joseph, if you're still unsure, just try pressing various combinations. Or open the thing.
Reply by ●September 26, 20142014-09-26
On Fri, 26 Sep 2014 12:38:00 +0300, Vladimir Ivanov <none@none.tld> wrote:> >On Fri, 26 Sep 2014, glen herrmannsfeldt wrote: > >> In comp.arch.embedded josephkk <joseph_barrett@sbcglobal.net> wrote: >> >> (snip) >> >>> I dispute that. PC keyboards report key down and key up to the mainboard >>> for all keys. That intrinsically gives them n-key rollover. Whether or >>> not it is processed that way is another matter, that is not done on the >>> keyboard. >> >> That means that they have the ability to report such keys, not >> that they actually do it. >> >> The do have to report shift, control, alt, and such, in addition >> to other keys that are pressed while some combination of those >> is down. >> >> To do a proper N-key rollover, you need a diode in series with >> each key switch. Without the diodes, you can get a large >> combination of more than 2 keys, but not all of them. > >Indeed. For a matrix keyboard relying on electrical contact, the lack of >diodes leads to 2-KRO. Optimized layouts, like placing modifiers on >carefully selected rows/columns, might somewhat hide this. > >Heck, even the classic IBM M keyboards, being membrane, are 2-KRO.No, Model-Ms are not membrane keyboards. They are "buckling spring".>Joseph, if you're still unsure, just try pressing various combinations. Or >open the thing.
Reply by ●September 26, 20142014-09-26
On Fri, 26 Sep 2014, krw@attt.bizz wrote:> On Fri, 26 Sep 2014 12:38:00 +0300, Vladimir Ivanov <none@none.tld> > wrote: >> >> Heck, even the classic IBM M keyboards, being membrane, are 2-KRO. > > No, Model-Ms are not membrane keyboards. They are "buckling spring".And the buckling spring moves a pivot (hammer), which presses on ... membranes. http://sandy55.fc2web.com/keyboard/inside_model_m.html
Reply by ●September 26, 20142014-09-26
On Thu, 25 Sep 2014 23:41:21 +0300, Vladimir Ivanov <none@none.tld> wrote:> >On Thu, 25 Sep 2014, Robert Wessel wrote: > >> The problem is in some ways analogous to keyboards without n-key >> rollover. A simple scannable array of switches (keys) can easily (and >> cheaply!) detect a switch closure (key press), but if you press two >> keys at once, it gets confused. Fortunately you don't see that on >> real keyboards anymore (the last time I saw a non-n-key-rollover >> keyboard was probably about 1980, before then it was actually an >> advertised feature), but you do still see the effects on many >> (particularly inexpensive) calculators (where it's even worse, since >> keyboard scanning is usually tied to the LCD refresh, so when you >> press several keys at once, you mess up the display as well). > >[more OT] > >Have to disappoint you, but almost all keyboards today are not N-key >rollover. The reason - using cheap membrane or rubber domes for contact. > >Currently there is some kind of a "revival" trend going on (particularly >fueled by gamers?), so there are few modern keyboards using >microswitches+diodes or capacitive sensing, but the mass market is still >2-KRO.Well I will be dipped... Sure enough, most are not, but they've done a pretty good job of hiding that from most users. Here's a test I came across that seems to work well. Hold down both shift keys, then type "the quick brown fox jumped over the lazy dog". The results were surprising on pretty much every keyboard I tried. OTOH doing something like typing and holding down asdf, then pressing 7878... works fine on all they keyboards I tried. There are clearly several separate scan matrices, enough so that I'm wondering how much they actually saved over doing real n-key.
Reply by ●September 26, 20142014-09-26
On Thu, 25 Sep 2014 09:38:51 -0700, Don Y <this@is.not.me.com> wrote:>On 9/25/2014 9:17 AM, Robert Wessel wrote: >> On Thu, 25 Sep 2014 06:52:15 -0700, Don Y <this@is.not.me.com> wrote: >> >>> Hi Theo, >>> >>> On 9/25/2014 2:11 AM, Theo Markettos wrote: >>> >>>> (Curiously, I installed Android 4.4 on an old (2010) laptop and discovered >>>> that the touchpad had been multitouch all along, just previously no drivers >>>> had enabled it) >>> >>> Hmmm... I'd never considered what (technologically) would differentiate >>> between single and multi-touch. To me, gestures have always been >>> "tracks through 2-space" >> >> The key difference is that "singletouch" devices can track only a >> single contact at a time. So they can't track the "squeezing" motion >> (two fingertips coming together) to cause a zoom-out (for example). >> IOW, multitouch is basically trying to resolve two (or more) gestures >> on the same device at the same time. > >Yes, I understand the difference in *application*. Rather, I was >commenting on what the differences in *implementation* would likely be. >I.e., how to resolve two (or more) "contact points" concurrently. > >> Technologically multi-touch is a bit more of a challenge, since you >> can no longer do a simple detector on each axis. Nor is a detector on >> each axis that can resolve more than one position enough (that would >> resolve to four possible positions with two touches, with no way of >> knowing which are the real ones). > >"Coordinated" (X+Y) detection can resolve the location of two >different contacts (if the technology can "see" both -- e.g., cameras >being an intuitive option). I have a whiteboard digitizer that could, >conceptually, track each of the five "utensils" (4 pen colors plus >an eraser) concurrently on that surface. (AFAIK, it makes no attempt >to do so -- people tend to write with one hand at a time and prohibiting >erasure WHILE writing seems an easy user-constraint)Sure a camera, ignoring the visibility problems, would work, but most simple touch devices are more along the lines of sensing a resistance or capacitance caused by your finger one the two axis. Or they do a simply number of rows and columns "sensors", where your touch causes a connect (again, not unlike a scanable keyboard matrix). None of those lend themselves to multi-touch.
Reply by ●September 27, 20142014-09-27
On Fri, 26 Sep 2014 12:38:00 +0300, Vladimir Ivanov <none@none.tld> wrote:> >On Fri, 26 Sep 2014, glen herrmannsfeldt wrote: > >> In comp.arch.embedded josephkk <joseph_barrett@sbcglobal.net> wrote: >> >> (snip) >> >>> I dispute that. PC keyboards report key down and key up to the mainboard >>> for all keys. That intrinsically gives them n-key rollover. Whether or >>> not it is processed that way is another matter, that is not done on the >>> keyboard. >> >> That means that they have the ability to report such keys, not >> that they actually do it. >> >> The do have to report shift, control, alt, and such, in addition >> to other keys that are pressed while some combination of those >> is down. >> >> To do a proper N-key rollover, you need a diode in series with >> each key switch. Without the diodes, you can get a large >> combination of more than 2 keys, but not all of them. > >Indeed. For a matrix keyboard relying on electrical contact, the lack of >diodes leads to 2-KRO. Optimized layouts, like placing modifiers on >carefully selected rows/columns, might somewhat hide this. > >Heck, even the classic IBM M keyboards, being membrane, are 2-KRO. > >Joseph, if you're still unsure, just try pressing various combinations. Or >open the thing.Guys, to report what is being reported to the mainboard n-key rollover in its full glory is necessary. It has little or nothing to do with some lower level circuit or switch properties. Think it through. ?-)
