Keypad scanning design problem!

[muahaha]

Can anybody help me about finding the nominal time value for a human pressing a key? Then i will try to write a program for keypad debouncing and scanning... I will try to use only two pins of a PIC microcontroller which supports stand by function for reduced power consumption, to scan and check 16 key and i want to catch the pressed key by using a capacitor's charge and discharge time and also i don't know this capacitor value and other remaining resistances. I am open for all design suggestions. Thanks for your interest!

[blinky465]

I suppose it depends who is doing the typing!
My sister spends ages pressing the keys (especially the tricky little blighters, like x and v which have a habit of becoming invisible on the bottom row) whereas I tend to touch-type quite quickly.

You can introduce hardware limits, but personally I like to control as much as possible in software. I would try to write my scanning routine to run as quickly as possible, include a debounce routine, then put a "check for release or time-out" routine before checking or responding to the same key again.

[treitmey]

I use this. Works well.
2.2uF cap
Note the interupt p3.2 which I run into the PIC ext interupt.
http://www.edn.com/contents/images/601828f1.pdf