Arduino

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 State change detection (edge detection)

 Often, you don't need to know the state of a digital input all the time, but
 you just need to know when the input changes from one state to another.
 For example, you want to know when a button goes from OFF to ON. This is called
 state change detection, or edge detection.

 This example shows how to detect when a button or button changes from off to on
 and on to off and how to count these changes.

 The circuit:
 - pushbutton attached to pin 2 from +5V
 - 10 kilohm resistor attached to pin 2 from ground
 
 created  27 Sep 2005
 modified 30 Aug 2011
 by Tom Igoe

 This example code is in the public domain.

 http://www.arduino.cc/en/Tutorial/ButtonStateChange

// this constant won't change: const int buttonPin = 2; // the pin that the pushbutton is attached to

// Variables will change: int buttonPushCounter = 0; // counter for the number of button presses int buttonState = 0; // current state of the button int lastButtonState = 0; // previous state of the button

void setup() {

 // initialize the button pin as a input:
 pinMode(buttonPin, INPUT);
 // initialize the LED as an output:
 //pinMode(ledPin, OUTPUT);
 // initialize serial communication:
 Serial.begin(9600);

}

void loop() {

 // read the pushbutton input pin:
 buttonState = digitalRead(buttonPin);

 // compare the buttonState to its previous state
 if (buttonState != lastButtonState) {
   // if the state has changed, increment the counter
   if (buttonState == HIGH) {
     // if the current state is HIGH then the button went from off to on.
     Serial.println("on");
     Serial.print("number of button pushes: ");
     Serial.println(buttonPushCounter);
   } else {
     // if the current state is LOW then the button went from on to off:
     Serial.println("off");
     Serial.println(" ");
   }
   // Delay a little bit to avoid inaccurate counting.
   delay(50);
 }
 // save the current state as the last state, for next time through the loop
 lastButtonState = buttonState;

}

Führe eine Funktion einmalig aus, wenn ein Button gedrückt ist, und einmalig etwas anderes, wenn er losgelassen wird

int buttonDown =0;
int inputPin = 5; //hier muss der Pin eingetragen sein, an dem der Button hängt

[...]

void loop(){
  
  if (digitalRead(inputPin)==LOW){
    buttonDown++;
  }
  
  if (buttonDown==1){
     DoSomethingOnceWhenPressed();
  }

  if (digitalRead(inputPin)==HIGH && buttonDown>0){
    DoSomethingOnceWhenReleased();
    buttonDown=0;
  }
  
}

Mache etwas alle x-Durchläufe

int loopCounter=0;
int alleXLoops = 15; //Führt eine Funktion alle 15 loops aus
[...]

void loop(){
  
  loopCounter++;
  
  if (loopCounter%alleXLoops==0){
    DoSomethingEveryXLoops(); 
  }

}