Example of realization of keyboard for small touch screens -- Carnegie Mellon's Zoomboard:
http://www.technologyreview.com/news/514096/a-qwerty-keyboard-for-your-wrist/ On Thu, Sep 19, 2013 at 1:06 AM, Werner Almesberger <[email protected]> wrote: > Felix wrote: >> I don't know if Werner have something in mind, > > Of course :-) > >> 1. Insert pin screen >> You have to insert a numeric pin of some fixed length. > > Not sure if a number is ideal. Letters may work better because > they're easier to remember. (More below.) > > I was thinking of the following input scheme: > - rotate in any direction to get the first letter/digit, > - rotate in the opposite direction for the second, > - change direction again for the third, etc. > - to delete one letter, press the center button, after which > you turn in the direction you want. > - waiting 0.5 s (or similar) ends input and starts validation. > > The display would show the current letter/digit plus briefly > the last one, so one could be sure that the button press didn't > alter it. > > The display has room for about three lines of reasonably large > text (~12 pt, bold and illuminated). During code entry, one line > could show the alphabet in a tiny (4 pixels wide) font. That > would be hard to read but all you really need to see is the > rough shape of letter. There would also be room for making some > of the letters a little larger. > > Have a little bar move below the letter to indicate the wheel's > "position" in the alphabet. That would allow to estimate the > distance to the next letter and "aim" better. > > I came up with the following equations: > > a = alphabet size, 10 for digits, 26 for letters, etc. > e = maximum entropy per letter, in bits > p = average number of positions from one to the next letter > u = difficulty of rotating the wheel by one position > r = difficulty of reversing the direction, in units of "u" > m = difficulty of remembering one letter, in units of "u" > t = total difficulty of entering one letter > E(a) = efficiency of an encoding, in bits per difficulty > > e = log2(a) > p = a/2 > t = p*u + r + m > > E(a) = e / t > > We can rewrite this to N(a) = log2(a) / (a + C) where N(a) is a > "normalized" efficiency (we don't care about the precise value) > and C is the per-letter difficulty in relation to moving the > wheel by a certain angle. > > Now, to find the maximum, we can either get out pencil, paper, and > our old calculus textbooks, play with www.wolframalpha.com (*), or > simply plot N(a) for various values of C (**) and make an eyeball > estimate. > > (*) E.g., for C = 20, a possible query would be > maximize log2(a)/(a+20) > > (**) E.g., for C = 20, and dropping the constant factor of ln(2), > plot [a=1:30] log(a)/(a+20) > > Now assign difficulty values, substitute "maximum" entropy with > real-life entropy, and run the math :-) > >> 2. Main screen >> You can scroll up or down among the names of stored data > > Yup. > >> 3. You choose an entry and see the data, scrolling through info. Long >> press takes you to main list: > > That, or simply have a "Back" item in the list or make the title > act like "Back". I like the general idea of using the length of a > button press, though. That's something that's often overlooked. > We may reserve it for administrative functions, though. > >> 4. If you leave the device on without interaction for more than 2 mins >> (e.g), the screen will be powered off and the cpu will go to deep sleep. > > I'm thinking of the following states (among other, more specialized > ones): > > - off: minimum power consumption, password safe is locked, > pressing the button a brief moment (longer than just hitting it, > to reduce accidental activation), turn on and show the PIN > dialog. > > - standby: display is off, LED is lit (possibly via PWM, to save > power), password safe is open. Switches to "off" after a while > or when turning the wheel. Goes to "open" when pressing the button. > > - PIN dialog: as described above. With automatic return to "off" if > left idle for more than a couple of seconds. > > - open: display is on, password safe is open. Goes to "standby" if > idle for a while. > >> Well, very basic, but is a idea to start, no? > > Yup, we're thinking in the same direction :) > > - Werner > > _______________________________________________ > Qi Hardware Discussion List > Mail to list (members only): [email protected] > Subscribe or Unsubscribe: > http://lists.en.qi-hardware.com/mailman/listinfo/discussion _______________________________________________ Qi Hardware Discussion List Mail to list (members only): [email protected] Subscribe or Unsubscribe: http://lists.en.qi-hardware.com/mailman/listinfo/discussion
