Simple Leonardo keyboard scanner to use Spectrum Keyboard as a USB keyboard
Two modes - FUSE and PC.
Fuse mode - just sends keypressed as they are presented. Symbol Shift mapped to LEFT CTRL PC mode - operates extended keypressed. All punctuation marks work ./,';:@ etc. EXTEND MODE + 1-0 = F1-F10 GRAPHICS MODE = F11 INV VIDEO = ALT SYM-SHIFT=L. CTRL EDIT = TAB
See code for which pin is used to switch mode.
All pins use pull-up resitors to remove interference and get pulled low when keys are pressed.