Chording Keyboards rev. 12-7-09

I have a lot of questions about "chording keyboards"?   Ok, so what are they?... usually one handed devices for entering in alphanumeric information to an electronic device using one hand. Why "chording?... this is the system used to get many characters from only a few switches. The first use of this process that I recall was learning Morse Code. I remember trying to build a translator for code being received on the 40 meter band. I built a mechanical device that would stair step through a chart and translate the incoming code to  a character. I used a single pushbutton switch to enter the dots and dashes. While doing the sketches of the layout I stumbled onto the concept of using an "Array" for switches to encode characters. I have since designed hardware and software for over a hundred devices that included a keyboard matrix. 

This all started with the search for a way to relieve Carpal Tunnel...  [Article Here]

The difference between a regular keyboard matrix and a chording keyboard layout is the the number of possible keys pressed. In most microcontroller circuits you will find only two possible lines are crossed in any given valid key press. In a chording keyboard you may press anywhere from one to five or even seven* switches.

There is a maximum possible number of combinations for every number of switches.

Single switch  on/off    2 possibilities
Two switches one on,  the other on,  both on 3 possibilities
Three switches Gets trickier, call them A B C,
then the possibilities are,
A, B, C, AB, AC, BC, ABC   		 7 possible. 
Four switches A, B, C, D, AB, AC, AD, BC, BD, CD, ABC, BCD,  ABD, ACD, ABCD  15 total.
Five switches Well you get the picture!!  

*Seven switches seems to be a common factor in many designs. There are a lot of designs that use 3 switches for thumb and the four finger switches. Since 4 switches give 15 possible combinations and 3 thumb positions give a total possible 3 X 15 = 45 characters total. This is more than enough for alpha + numeric + function keys. Seven switches would be a Septambic keyer

                            Names for various numbers of switches

uni-ambic: one pushbutton switch or key;    also referred to as Iambic

bi-ambic: two pushbutton switches or keys;

tri-ambic: three pushbutton switches or keys; ...

pent-ambic: five pushbutton switches or keys; ...

sept-ambic: seven pushbutton switches or keys; ...  This is commonly used word

multi-ambic: many pushbutton switches or keys;
  

A way to validate the words in the list above is by
the number of GOOGLE hits per word searched

uniambic                   22 hits

iambic              173,000 hits          3,420 hits for "iambic + keyer"  (Ham Radio)

monoambic                 0 hits

biambic                      20 hits           probably not a word

diambic                 196 hits       only 3 valid

triambic                        9 hits

quadrambic                  0 hits   

tetrambic                       0 hits

pentambic                   50 hits          probably not a word

heptambic                      0 hits

septambic                 128 hits

octambic                        1 hit          (music only... air guitar)

hexambic                        0 hits

decambic                        0 hits

multiambic               130 hits        all Google hits are for keyer's

polyambic                 8 hits    

"iambic" means "one short syllable followed by one long syllable or of one
  unstressed syllable followed by one stressed syllable" (mweb dictionary).

 

Examples

Uniambic                http://electronicsusa.com/mk.html       1 switch Key for Ham Radio and Morse
                                                         By definition Ham Radio Operator's Iambic keyer's have 2 switches - dot/dash.

Pentambic                  http://www.bellaire.demon.co.uk/codes.htm    5 Switches chording example (actually has 9 keys
                                                                                                                                   for full command structure)

Septambic                  http://www.cs.vassar.edu/~priestdo/chordhack/      7 Switches
                                                     This is the best home built design I have seen.
                                                     Using Phone handset rest... http://www.cs.vassar.edu/~priestdo/chordhack/phonerest/ 

                                      http://wearcam.org/septambic/    This is one you build from scratch.
                                                                                      Best looking ergonomic design

Multiambic                ? Many Switches

Can anyone tell me: Why is the "Standard Keyboard" layout (QWERTY)
 is not patented but almost all chording devices are????

I would really love to hear from anyone who knows
 a Public Domain Chording scheme for a Septambic Keyer.

Links:

http://www.datahand.com/    two separate keyers one for each hand

http://www.thumbscript.com/howitworks.html   9 switch developed for cell phones

http://www.comp.utas.edu.au/users/nholmes/prfsn/tp2Jl.htm  8 switch based on ASCII

http://wetpc.com.au/html/technology/ruggedised.htm#kordpad  5 switch - Marine use
This is an example of an application that uses graphics on screen to tell you which fingers to chord with. This may be a way to build a trainer???

http://www.infogrip.com/product_view.asp?RecordNumber=12      7 switch desktop

http://www.chordite.com/        Interesting,  Another Patent, 8 switches

http://cuddlepuddle.org/~adam/pickey/index.html  PIC based 

http://www.4starelectronics.com/  Source of Obsolete IC's

http://xaphoon.com/dataegg/      aka...  DataEgg  discontinued research... 4 fingers + other switches

http://www.ekatetra.com/        12 keys

http://www.langdoncrawford.com/nime/agPrototype02.htm   8 keys for music... (air Guitar) 

http://www.gkos.com/  &   http://www.gkos.net/         6 key

http://onut.net/projects/MICK/MICK-second-design.html   8 key Braille format (6 dot or 8 dot) & GKOS

http://chorder.cs.vassar.edu/    7 key

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