用Tinkercad学arduino之 状态变化检测（边缘检测） 按4次亮灯

/*

  State change detection (edge detection)
  状态变化检测（边缘检测）

  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.
   
  通常，您不需要知道状态一直使用数字输入，但您只需要知道输入何时从一种状态变为另一个。 例如，您想知道什么时候按钮从OFF变为ON。 这就是所谓的状态变化检测或边缘检测。
 
  This example shows how to detect when a button or button changes from off to on  and on to off.
  本示例说明如何检测按钮或按钮从关闭变为打开，然后从打开变为关闭。

  The circuit:
  * pushbutton attached to pin 2 from +5V
  * 10K resistor attached to pin 2 from ground
  * LED attached from pin 13 to ground (or use the built-in LED on  most Arduino boards)
  电路：
   * 按钮从5V连接到引脚2
   * 10K电阻从地连接到引脚2
   * LED从引脚13接地（或使用大多数Arduino板上的内置LED）

  This example code is in the public domain.
  http://www.arduino.cc/en/Tutorial/ButtonStateChange
*/

int buttonState = 0;

int lastButtonState = 0;

int buttonPushCounter = 0;

void setup()
{
  pinMode(2, INPUT);
  Serial.begin(9600);

  pinMode(13, OUTPUT);
}

void loop()
{
  // read the pushbutton input pin
  buttonState = digitalRead(2);
  // 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 += 1;
      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 debouncing
    delay(5); // Wait for 5 millisecond(s)
  }
  // save the current state as the last state, for
  // the 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 devision of two numbers
  //通过检查按钮按下计数器的模数，每四个按钮按下一次即可打开LED一次。
  //模函数返回两个数相除的余数
  if (buttonPushCounter % 4 == 0) {
    digitalWrite(13, HIGH);
  } else {
    digitalWrite(13, LOW);
  }
}