Two-Thumb Keypad Chording
The Motorola Razr keypad was used as the model a 12-key phone keypad
Updates:
The paper has now been presented at MobileHCI 2009. It received a
Best Paper Nomination. Also, it received some press
here.
My Keynote '09 Slides.
When designing a text entry system for mobile phone keypads, a designer needs to overcome the ambiguity that arises from mapping the 26 letters of the roman alphabet to only 12 keys (0–9, *, #). I created a novel two-thumb chording system for text entry on a standard 12-key mobile phone keypad and a performance model based on Fitts’ Law for an expert user. The model provides a behavioral description of the user and predicts a text entry rate of 55.02 wpm.
Our method consists entirely of one and two-key chords using only the standard 12 keys found on mobile phone keypads. Keys 2–9 are used as character keys while the *, 0, # and 1 keys are used as chording keys. By pressing any of the character keys alone the user enters the first letter displayed on the key. Simultaneously pressing a character key in combination with the * key allows the user to enter the second letter displayed on the key, pressing a character key with the 0 key enters the third character and pressing a character key with # key enters the fourth character in the case of “s” and “z”. The space character is entered by pressing the # key alone. The table below shows the keymap for generating all of the letters and the space character. Numbers are entered by using the 1 key as a chording key to select the numeral on the key. By pressing 1 alone, the user enters 1. By pressing 1 in combination with any other number, the user enters that number. Capitalizing a letter is performed by first pressing the 0 key alone and then entering the character. Rapidly pressing 0 twice allows the user to enter caps-lock mode, pressing 0 again once reverts to the previous mode. Common symbols can be accessed by pressing the # key and character keys other than 7 or 9.
| Chording Key | |||||
| Character Key | None | * | 0 | # | 1 |
|---|---|---|---|---|---|
| None | Space | 1 | |||
| 2 | a | b | c | 2 | |
| 3 | d | e | f | 3 | |
| 4 | g | h | i | 4 | |
| 5 | j | k | l | 5 | |
| 6 | m | n | o | 6 | |
| 7 | p | q | r | s | 7 |
| 8 | t | u | v | 8 | |
| 9 | w | x | y | z | 9 |
Related Documents
A Model of Two-Thumb Chording on a Phone Keypad.
Nirmal Patel, James Clawson and Thad Starner.
Proceedings of MobileHCI 2009. Bonn, Germany, September 15-18. 2009.
ACM Best Paper Nomination
Two-Thumb Chording
Poster. Georgia Tech Undergraduate Research Symposium.
Phong Su Si, Nirmal Patel and Thad Starner.
Spring 2010.
Best Poster Award for College of Computing
