This software runs on an Arduino Leonardo board connected to the keyboard of a Sinclair ZX81 home computer, converting the device into a USB keyboard.
The program is derived from code written by and copyright Dave Curran of Tynemouth Software (http://blog.tynemouthsoftware.co.uk/2012/02/arduino-based-zx81-usb-keyboard.html) but modified to allow the entry of non-alphanumeric characters.
As per Dave's code, when un-Shifted the keyboard will yield lowercase letters and numbers. Holding down Shift will yield uppercase letters, and the cursor keys may also be used. If the Function/New Line key is pressed while Shift is held down, the keyboard will enter 'symbol' mode: pressing a subsequent key (without Shift) will produce the symbol shown on the key in red.
A number of now-important symbols were omitted from the ZX81 keyboard. These have been added to some of the keys which display Sinclair Basic keywords in red.
Note: whether you get the # or the Sterling symbol will depend upon your host system's own keyboard localisation settings.
##The Keys
Please refer to a picture of the ZX81 keyboard (http://smittytone.files.wordpress.com/2014/02/p1020039.jpg?w=810)
Note _ indicates no key action, however the key E in Symbol mode WILL generate an underscore
NO SHIFT
1 2 3 4 5 6 7 8 9 0
q w e r t y u i o p
a s d f g h j k l NewLine
z x c v b n m . Space
SHIFTED
Escape _ _ _ _ LEFT DOWN UP RIGHT _ Backspace
Q W E R T Y U I O P
A S D F G H J K L SymbolSelect
Z X C V B N M , #
SYMBOL MODE
[ ] { } LEFT DOWN UP RIGHT ! Backspace
" _ underscore \ ^ % $ ( ) "
@ | ~ _ _ * - + = NewLine
: ; ? / * < > ' #