Freenove Ultimate Starter Kit, Manual

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67 Chapter 2 Button & LED █ www.freenove.com
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//if changing-state of the button last beyond the time we set, we considered that
//the current button state is an effective change rather than a buffeting
if ( millis () - lastChangeTime > captureTime ){
//if button state is changed ,update the data.
if ( reading != buttonState ){
buttonState = reading ;
//if the state is low ,the action is pressing
if ( buttonState == LOW ){
printf ( "Button is pressed!\n" );
ledState = ! ledState ;
if ( ledState ){
printf ( "turn on LED ...\n" );
}
else {
printf ( "turn off LED ...\n" );
}
}
//if the state is high ,the action is releasing
else {
printf ( "Button is released!\n" );
}
}
}
digitalWrite ( ledPin , ledState );
lastbuttonState = reading ;
}
return 0 ;
}
This code focuses on eliminating the buffeting of button. We define several variables to save the state of LED
and button. Then read the button state in while () constantly, and determine whether the state has changed.
If it is, record this time point.
reading = digitalRead ( buttonPin ); //read the current state of button
if ( reading != lastbuttonState ){
lastChangeTime = millis ();
}
millis()
Returns the number of milliseconds since the Arduino board began running the current program.
Then according to just recorded time point, judge the duration of the button state change. If the duration
exceeds captureTime (buffeting time) we set, it indicates that the state of the button has changed. During that
time, the while () is still detecting the state of the button, so if there is a change, the time point of change will
be updated. Then duration will be judged again until the duration of there is a stable state exceeds the time
we set.