If you use a xy matrix then diodes are required for each switch to check for
multiple key presses otherwise it works ok (fell in to that one myself when
reading personality jumpers)
If you do the code in a loop then the scan code can be quite small it only
requires a single decrement counter (for the colums) and the FSR to store the
rows in consecutive memory locations. Go round the loop onece for each colum.

Steve.....