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Wolfgang Hottgenroth
2018-05-11 14:39:55 +02:00
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@ -1,10 +1,14 @@
<!-- { "title": "Yet Another Debouncing Method" } -->
<h1>#title#</h1>
<p>
You can find several approaches for debouncing mechanical switches on the Internet, some work better, some not so good.
</p>
One common approach is to ignore events in an ISR when they come too fast:
<p>
One common approach is to ignore events in an ISR when they come too fast:<br/>
[code language="C"]
<pre><code class="C">
void count() {
static uint32_t lastEvent = 0;
uint32_t currentEvent = micros();
@ -18,26 +22,25 @@ void setup() {
pinMode(REED_PIN, INPUT_PULLUP);
attachInterrupt(REED_PIN, count, FALLING);
}
[/code]
</code>
</pre>
This works very good when only the tipping of a switch is relevant.
</p>
When also the time the button was pressed is relevant and when it is especially necessary to distinguish between a short and a long press this approach doesn't work anymore.
<p>
When also the time the button was pressed is relevant and when it is especially necessary to distinguish between a short and a long press this approach doesn't work anymore.<br/>
Since I couldn't remember the approaches I read about earlier I've sketched this state machine:
Since I couldn't remember the approaches I read about earlier I've sketched this state machine:<br/>
<img src="files/20180430110848869_0001.jpg" width="500"/>
<!--more-->
<br/>
(The double-lined states are action-states which send out the related information.)<br>
At least for me, this approach is working very reliable so far, I'm quite happy with it.<br>
<img src="https://a385e5.files.wordpress.com/2018/04/20180430110848869_0001.jpg" alt="20180430110848869_0001.jpg" width="2332" height="3307" class="alignnone size-full wp-image-901" />
(The double-lined states are action-states which send out the related information.)
At least for me, this approach is working very reliable so far, I'm quite happy with it.
[code language="C"]
<pre><code class="C">
enum tPressedState { psHIGH, psLOW, psACCEPTED_LOW, psLONG_START, psLONG_CONT, psLONG_CONT_SEND, psLONG_END, psSHORT, psINVALID };
typedef struct {
@ -135,8 +138,13 @@ static void buttonHandler(tButton *button) {
button-&gt;lastStateChange = currentMicros;
}
}
[/code]
</code>
</pre>
</p>
Find it embedded in the code of a small ESP8266-based switch thing I'm using in my home automation setup (home grown control code (https://gitlab.com/wolutator/dispatcher_ng), homegear (https://homegear.eu/) for device integration and openHAB (https://www.openhab.org/) as user interface) here: https://gitlab.com/wolutator/MySwitch.
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<p>
Find it embedded in the code of a small ESP8266-based switch thing I'm using in
my home automation setup (home grown control code (<a href="https://gitlab.com/wolutator/dispatcher_ng">on gitlab</a>),
<a href="https://homegear.eu/">homegear</a> for device integration and <a href="https://www.openhab.org/">openhab</a>
as user interface) <a href="https://gitlab.com/wolutator/MySwitch">here on gitlab</a>.
</p>