Handy Tech
Elektronik GmbH
Active Braille
External Keyboard
Page 72
6
External Keyboard
An external keyboard may be connected directly to the Active Braille. 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 Active Braille 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 described 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
Active Braille's keyboard driver needs further information indicating how it is to implement
the encoded key stroke information. Therefore a table for assigning key strokes to
characters must be present in the Active Braille, the keyboard layout table.
The Active Braille already contains a fixed, programmed keyboard layout table for a
German keyboard, as well as a downloadable keyboard layout table. This table is called
"kbdlyout.hsf" for all languages. 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 Active Braille has been reformatted. When the
Active Braille is turned on, it checks whether an error-free, downloaded table is present: if
not, it generates the warning message
'Warning: No keyboard layout file 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 Active Braille, because in this case it is still
possible to attach the keyboard later.
The keyboard layout table appropriate to your country is already loaded into the Active
Braille for shipping. However, you can also modify this file, or create a new one and then
load it into the Active Braille. This means that the existing keyboard layout will be
overwritten.
