Hello Gerhard,
On 04/28/2014 03:44 PM, Gerhard Sittig wrote:
On Fri, 2014-04-25 at 12:20 +0200, Przemyslaw Marczak wrote:
This change prevents gpio keys bouncing by adding 50 ms delay
when key pressed condition met.
[ ... ]
@@ -105,6 +105,10 @@ static int check_keys(void)
if (key_pressed(KEY_VOLUMEDOWN))
keys += KEY_VOLUMEDOWN;
+ /* Avoids gpio keys debouncing */
+ if (keys)
+ mdelay(50);
+
return keys;
}
The approach might have helped in your case, since you tested it
and found it's good. I'm just wondering whether the code really
does correct de-bouncing.
The delay does decrease the polling frequency (assuming that the
routine is called in a loop). But you return data that was
sampled before the delay. You don't re-fetch samples after the
delay. And this would not necessarily help either, I'm afraid.
In case the GPIO (or the key_pressed() call) does debouncing, you
wouldn't need it here. If the key_pressed() result still is
bouncy, then the above logic would not debounce it. What you
need is some kind of "trigger" where you notice that the line
levels are changing, and a delayed fetch of the lines' values
after they have settled. Without the first condition, you always
have the risk of sampling arbitrary data that does not reflect
the keys' status.
nit: The comment still appears to be misleading, you don't want
to avoid debouncing. :)
virtually yours
Gerhard Sittig
This is right notice. Actually the problem was not a key bouncing.
The right problem is about the menu loop where check_keys() is called
too many times for a one second.
And changing menu position few times in a second is useless and hard to
choose proper menu option.
Putting delay into check_keys() function was good enough to make this
menu more useful but in fact this was not a solution for key bouncing.
Function check_keys() should be as fast as it could be.
So I think that I need only increase a delay in the menu loop which is
now 100ms.
Increasing it to 200ms gives good results. It's a simple solution.
What do you think about this?
Thank you for comments.
--
Przemyslaw Marczak
Samsung R&D Institute Poland
Samsung Electronics
p.marc...@samsung.com
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