Peter:
Your simpler solution only is able to queue a transition in only one direction. This is quite suitable for applications such as yours as a keypad input where a activate on "make" is the desired action. The code I showed has been used in a more general purpose application where the inputs may come from other types of control signals there it may be necessary to detect the "release" condition or even in applications where the ON and OFF both need to be monitored.

I just wanted to point this out for the benefit of others that may be trying to figure out why my code is more complicated. I used a four sample shift register type filter so that the sequence of zeros or sequence of ones can be independantly detected.

Michael Karas