dhteensy is a hardware hack and a new firmware for Datahand keyboards using the Teensy++ development board to add native USB support and full layout customization.
I got the idea from Glenn Boyer's geekhack.org post (see below) and decided to implement something very similar. The idea is to use a Teensy++ board and hook up the VCC, GND and the required data pins to the CPU socket on the Datahand's main circuit board in place of the original 8051 clone CPU.
The Teensy++ is a very nice AVR based board similar to Arduino that makes it easy to implement USB HID devices. It has plenty of I/O pins and it is the same size as the original CPU used in the Datahand so it's easy to make a converter.
The firmware is written in C using the AVR gcc port. The Makefile and the USB HID code came from the examples provided by PJRC for the Teensy++. The current firmware is very simple and doesn't have all the functionality of the original and it is somewhat customized to my own preferences. It has some assumptions about which Teensy pins are used to access the Datahand, this should be easy to change if you implement the converter differently.
http://geekhack.org/showwiki.php?title=Island:12212 http://github.com/JesusFreke/DHFirm