Hi Mahdy,


BOUNCING:
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All mechanical contacts when pushed to meet eachother do make and break several times before finally they come to permanent make under applied pressure of fingure or anything that pushes the contacts (switch).

This intermittent condition is not desired because it will give as many pulses as the makes and breaks, whereas the user intended just one and only one make.

Such conditions, depending on the mechanical switch type last from 10 to 100 milli seconds.

DEBOUNCING:
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So, by philosophy, the easy way out is just wait for 100 mSec. right after the first make is encountered by the micro and then test again if make still exists (this means that it was an intended make and it will not chatter any more) then do the action on that key press.

This can be implemented in software very easily.


Happy debouncing

Simon