An experiment: (max) 15 keys using 4 pins, debounced, full IT controlled

For decoding I'm using cheap Si diodes like 1N4148:




Key press is sensed via PORTB change interrupt, and TIMER2 is used for a 20 msec debouncing.
Only one key can be pressed at a time, then it must be released.

I have written a demo program to demonstrate the concept:
Attached is a ZIP with the basic source, the HEX file and the DSN.

Sorry, but I'm using assembly snippets so for recompiling use Proton 3.5.0.6 (max).

Greetings
zuisti