Actilino
External Keyboard
Page 76
6
External Keyboard
An external keyboard may be connected directly to the Actilino. Keyboards of any make or
model may be used, provided they comply with the following requirements:
•
USB connection
•
low current consumption (recommended 30 mA with LEDs turned off)
The external keyboard transmits your key strokes to the Actilino in the same way as the
internal Braille keyboard. You can therefore operate both an external and the internal
keyboard in parallel. Please refer to chapter "Installation" for the procedure for connecting
an external keyboard.
Please remember that all the information in this section applies only to an external keyboard,
not to the built-in Braille keyboard.
6.1 General
Any keyboard transmits encoded data indicating which key has been pressed or released.
These data do not in themselves contain any information about what this key stroke means,
i.e. which character it should generate. That information is assigned by the so-called
keyboard driver and depends on the desired language. This means, for example, that if a
U.S. English keyboard layout has been selected, the character ":" is realized by pressing
"Shift ö" on a German keyboard.
Depending on the language (which means on the keyboard layout currently in force), the
Actilino's keyboard driver needs further information on how it is to implement the encoded
key stroke information. Therefore, a table for assigning key strokes to characters must be
present in the Actilino, the keyboard layout table.
The Actilino already contains a fixed, programmed keyboard layout table for a German
keyboard as well as downloadable keyboard layout tables for the languages that can be
chosen in the menu. The keyboard layout tables for the different languages are named after
the following scheme: "Language_KBDLYOUT.hsf". The internal keyboard layout table is
always activated when no downloadable keyboard layout is found. This is the case, for
example, when no files at all are stored on the media after the Actilino has been reformatted.
When the Actilino is turned on, it checks whether the downloadable table is available for the
chosen language. If not, it generates the warning message:
'WRN: KBD layout not found. Using standard layout. '
and switches automatically to the default internal table. The warning is even generated when
no external keyboard is connected to the Actilino because in this case it is still possible to
attach the keyboard later. You can also change or create the files with the keyboard layout
tables by yourself and transfer them to the Actilino afterwards.
6.2 Keyboard Keys
In this section, you will find comments on some characteristics of using an external
keyboard. They are generally caused by the fact that there are keys on a keyboard that
make no sense when used in conjunction with the Actilino.
