Using mister-e's Matrix Keypad module you can have 64 keys if you want.
Requires 2 full 8-bit ports, 8 rows, 8 columns.

OR ... 8 rows, 4 columns = 32 keys
OR ... 4 rows, 8 columns

It's essentially an extension of the meLabs keypad example with more features.

Matrix Keypad routine
http://www.picbasic.co.uk/forum/showthread.php?t=3250
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