| ??? 09/05/04 15:14 Read: times |
#76918 - RE: debouncing for matrix keypad ? Responding to: ???'s previous message |
Dear Michael,
Hello, thank you very much for your reply. Now if that particular microswitch press was supposed to be the exact time a life saving defibrillation pulse was supposed to be delivered to a patient on the hospital operating table we may conclude that we cannot determine if the pulse got delivered or not. I quite agree that in some critical applications multiple reading may be necessary but 2 points : 1- matrix keypads usually are used for a user interface and as the smallest perceptionable time for human is in matter of 100 ms then 10-30 ms is not important for most applications. 2- as it comes to measuring absolute and exact( in matter of microseconds) time of press or release of a microswitch. I’m afraid that even debouncing can not help that because sampling rate is in matter of 15-30 ms. ..but then you need to sample multiple times to be able to detect the approximate switch transition times....from "0" -> "1" or from "1" -> "0" As It comes to measuring approximate switch transition times I’m afraid using software debounce doesn’t give more accurate answer but it gives a safe answer. In other words when using debounce in keypad scanning routines it will not report a pressed key unless a safe edge of the microswitch has been reached ( an edge that most likely will not bounce again). again is not a more accurate edge but it is a safer edge because the more accurate edge was the first falling or rising edge that will continue to bounce for sometime. so the question again is: is it really necessary to debounce matrix keypad for normal applications ? I hope I didn’t miss anything in your reply. Thank you very much again Reza fallahati |
