| /* | |
| 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. | |
| The circuit: | |
| - pushbutton attached to pin 2 from +5V | |
| - 10 kilohm resistor attached to pin 2 from ground | |
| - LED attached from pin 13 to ground through 220 ohm resistor (or use the | |
| built-in LED on most Arduino boards) | |
| created 27 Sep 2005 | |
| modified 30 Aug 2011 | |
| by Tom Igoe | |
| This example code is in the public domain. | |
| https://www.arduino.cc/en/Tutorial/BuiltInExamples/StateChangeDetection | |
| */ | |
| // this constant won't change: | |
| const int buttonPin = 2; // the pin that the pushbutton is attached to | |
| const int ledPin = 13; // the pin that the LED 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: | |
| buttonPushCounter++; | |
| 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"); | |
| } | |
| // Delay a little bit to avoid bouncing | |
| delay(50); | |
| } | |
| // save the current state as the last state, for next time through the loop | |
| lastButtonState = buttonState; | |
| // turns on the LED every four button pushes by checking the modulo of the | |
| // button push counter. the modulo function gives you the remainder of the | |
| // division of two numbers: | |
| if (buttonPushCounter % 4 == 0) { | |
| digitalWrite(ledPin, HIGH); | |
| } else { | |
| digitalWrite(ledPin, LOW); | |
| } | |
| } | |