The SpiffChorder is an implementation of chording keyboard Chorded keyboard. It is an input device where characters are typed by pressing multiple keys at the same time. It was designed to entirely replace a computer keyboard. Specifically, the SpiffChorder consists of the hardware and software needed to emulate a conventional usb keyboard in an object or objects with only a small number of keys or switches on it. For the purposes of building one, you can think of it as functionally consisting of six main components, three hardware, and three software:
The circuit design of the SpiffChorder allows for up to 8 keys for chording and up to 3 additional keys that can be used as modifiers (ctrl, alt, shift). The implementation that sees the most use consists of a total of 7 keys all used for chording in this case the modifiers are also entered as chords.
No, since you can change the code and you can modify the keybindings you could render it unstable. You could create a keymap where you have no way to get out of a special mode or state unless you unplug it (for example, no way to undo caps lock). However, if you exercise a little planning and care in designing your keymaps, this should not be an issue. The SpiffChorder device and the Modified NASA keybindings have been in daily use for over two years so we feel safe saying that this combination is “stable”.
The software is open and free. You only pay for the parts of your chorder. The circuit can be built for under $25 US. The input device cost depends on what you want to use for switches and such, if you want a 7 key desktop or handheld chorder you can do that with good keys for under $10 US, if you want to embed a sensor system for chording in the latest haute couture, then you may spend a little more. In addition you will need access to a programmer for the atmel microprocessor to load the code the first time. If you don’t have that Greg will program your chip for you at no cost. Just send him a chip and a self addressed stamped envelope. Contact him first to confirm address and schedule. However, programmers are not that expensive and depending on where you live, it may be cheaper to make or even buy a programmer than to mail chips back and forth.