Post Reply 
DM42 available for order!!!
12-22-2017, 08:16 PM
Post: #29
RE: DM42 available for order!!!
(12-22-2017 07:17 PM)Jeff O. Wrote:  For de-bouncing, isn’t the issue, from the keyboard handler’s perspective, “hey, I just detected a key press and release, how long should I wait before accepting another press of the same key as an intentional second press of that key?”

That is the correct algorithm to detect a proper key register.
As soon as a ON key is detected by the software routine, it must register it and enter a waiting cycle using a counter for at least, say a 100mS, before listening again to new key presses (the keyboard routine can use a basic poll scanning method, or else a more sophisticated hardware interrupt handler).

In this way, the multiple successive ON-OFF-ON impulses resulting from pressing a key, no matter how good is the key or how hard you press it, will be interpreted as a single key press.

Of course this bouncing issue will be worse on lower quality keyboards (easily oxidizable metal contacts requiring more mechanical pressure to minimize the ON-OFF-ON train pulses), but as far as I know, it is impossible to eliminate it at the hardware level alone.
A proper debouching routine must handle it correctly, even if it takes a longer waiting cycle, like 200mS or even 300mS, to make sure that, at very least, each key registers only once when pressed.

Jose Mesquita
RadioMuseum.org member

Find all posts by this user
Quote this message in a reply
Post Reply 


Messages In This Thread
DM42 available for order!!! - Namir - 12-18-2017, 07:40 PM
RE: DM42 available for order!!! - Logan - 12-18-2017, 07:46 PM
RE: DM42 available for order!!! - Namir - 12-18-2017, 08:35 PM
RE: DM42 available for order!!! - smp - 12-18-2017, 09:11 PM
RE: DM42 available for order!!! - salvomic - 12-18-2017, 09:55 PM
RE: DM42 available for order!!! - grsbanks - 12-19-2017, 11:15 AM
RE: DM42 available for order!!! - salvomic - 12-19-2017, 11:22 AM
RE: DM42 available for order!!! - smp - 12-19-2017, 03:28 PM
RE: DM42 available for order!!! - larthurl - 12-19-2017, 06:36 PM
RE: DM42 available for order!!! - Logan - 12-19-2017, 03:50 PM
RE: DM42 available for order!!! - Logan - 12-19-2017, 06:31 PM
RE: DM42 available for order!!! - Jeff O. - 12-22-2017, 07:17 PM
RE: DM42 available for order!!! - jebem - 12-22-2017 08:16 PM
RE: DM42 available for order!!! - Logan - 12-20-2017, 02:12 PM
RE: DM42 available for order!!! - jebem - 12-22-2017, 01:47 PM
RE: DM42 available for order!!! - salvomic - 12-22-2017, 01:53 PM
RE: DM42 available for order!!! - Logan - 12-22-2017, 06:55 PM



User(s) browsing this thread: