DHFirm: DataHand firmware
Author: Ben Gruver (JesusFreke@JesusFreke.com)

This is a firmware written from scratch in 8051 assembly for the DataHand
keyboard, which uses an Atmel AT89C55WD microcontroller.

I wrote this mainly because I couldn't get the exact button mapping I wanted
with the stock firmware, just using key maps on the computer. The mapping is a
modified dvorak-style mapping. The modifications were mostly to prevent common
keys from being mapped to "north" buttons (and in some cases east/west),
because those seem to be less somewhat more difficult to press than the well
and south keys.

The firmware isn't as functional as the "stock" firmware. For example, it
doesn't support any type of runtime configuration, the mouse functionality,
macros, etc.

You can find (and modify) the key map that it uses in ScanButtons.asm. The
*Map tables (NormalMap, NASMap, etc.) store the PS2 scan code for each key in
each mode. And then further down, in the HandleButtonPress_* and
HandleButtonRelease_* procedures, the appropriate *Press or *Release procedure
is called for each key in each mode - depending on whether it's a normal or
extended scan code (or a few other possibilities)

The source should be compatible with most 8051 assemblers that use the Intel
assembly format. I personally use the MCU 8051 IDE, with the ASEM-51 assembler.
Both are FOSS tools.

Features:
- The firmware currently supports 4 modes - normal, NAS, function and game.
Normal, NAS and Function modes are roughly equivalent to the same modes in the
official firmware. Each mode is represented by one of the LEDs on the right
hand unit. 
- Game mode is designed to be a "left hand only" mapping for use in games.
Every left hand button is mapped to a key, and all 3 modifiers are available
via the left thumb buttons. The game mode is activated by pressing and holding
the "normal mode" key, and then pressing ";" (left hand, pinky, south button). 
- It has a left-hand only shortcut for cut/copy/paste that is activated by
using the "normal mode" key as a modifier with the QWERTY equivalent x,c,v keys
(left hand, ring, middle and fore finger, south).
- Support for typematic repeat


Known Issues:
- There is something fishy going on when booting some machines while the
keyboard is plugged in, with this firmware. The keyboard will lock up, and the
computer won't recognize it. The workaround is to plug a normal PS2 keyboard in
during bootup, and then once the OS has booted, switch the keyboards and use the
DataHand.
- It doesn't seem to play well with the one PS2 to USB converter that I tried.
- I haven't added support for the num lock/caps lock/etc. LEDs on the left hand
unit