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The GKOS Keyboard Scanning

There are several methods to implement the scanning of the GKOS keyboard

1. Basic Scanning

In the basic typing and key scanning method, the successively pressed key combinations do not overlap, i.e. all keys must be released before the next charater is typed. The typed character is determined by those keys that have been down since the previous situaton when there were no keys pressed. The character appears on the screen at the moment all keys are released. Holding down the key combination for e.g. 2 seconds (typematic delay) will start the automatic repeat of the character. - This is the standard simple method requiring very little processing power, allowing typing speeds to ca.50 wpm.

2. Intelligent Scanning

This method of typing and key scanning is similar to the basic method above except that some amount of overlapping is allowed. The start and stop times of overlapping key presses, as well as the durations of the 'key down' situations are analysed and compared with each other in an intelligent way to decide which key presses go together to form a single character. - This is the standard method that requires more processing than the basic scanning but is practical with higher typing speeds (beyond 50 wpm).

3. Teach mode

In teach mode, in order to find the right character, it is possible for the user to change the combination pressed if not all keys are released. While changing the combination, the corresponding character will appear at the (same) cursor position. When all keys are released the character corresponding to the last combination is printed and the cursor is advanced. The typematic delay (auto repeat) is not applied in this mode. This function may be applied to symbols including 1 to 3 simultaneous key presses only, showing a blank cursor position for other combinations. - This method makes it possible for a beginner to type text correctly without looking at the instructions.

4. Special mode

This is an enhancment of Intelligent Scanning so that a different typing technique can be used: if the same key (or two) is required in successive characters, supposing they are letters, it is not necessary to release it (or them) inbetween. The character decision is partly based on the fact that letters are always formed in a certain way, namely 1+0, 0+1, 2+0, 0+2, 2+1 or 1+2 simultaneous keys. Some overlapping is allowed. The standard way of typing, if regular in form, also gives a correct result. - The special mode increases the possible typing speed if the analysis of key presses is implemented successfully, but additional practicing is required to achieve this. (for further study)

The special mode makes it possible to type chordons instead of separate chords. Read more. The Chordon technique also makes it possible to enter complete words by just typing two characters as a chordon. See the Table of GKOS Shortcuts based on this principle.

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