OK, I got bored last night and got to thinking if I could interface a 3x4
matrix keypad using less than 7 lines without shift registers etc.  I
suspect it must have been done, but I figured out a (possible) solution
which uses only 4 lines and some diodes.

I haven't got any hardware to try this out on at present, but I'd be
interested in any comments.  I started writing the code in Hitech C but
figured that I had to get to grips with PIC assembler some time so this is
my first attempt, and is therefore probably full of standard mistakes and is
most definately in need of optimisation.

Check it out on:
http://www.mikerj.clara.net/keypad.html

and let me know why it won't work :o)

Regards

Mike Rigby-Jones
mrjones@nortelnetworks.com