State change detection 状态变化检测

这段代码是一个Arduino示例程序，名为“State change detection (edge detection)”，用于检测按钮状态的变化（即边缘检测）。

/*
  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
 * 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)

 created  27 Sep 2005
 modified 30 Aug 2011
 by Tom Igoe

This example code is in the public domain.

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

 */

// 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
      // wend 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
      // wend 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);
  }

}

代码功能

状态变化检测：代码通过检测按钮从关闭到打开（或从打开到关闭）的状态变化来触发事件。
应用场景：这种代码常用于需要检测按钮按下次数或状态变化的场景，例如计数器或简单的交互式装置。

代码逐行解释

1. 注释部分

这是代码的注释部分，说明了代码的功能和硬件连接方式

/*
  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
 * 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)

 created  27 Sep 2005
 modified 30 Aug 2011
 by Tom Igoe

This example code is in the public domain.

 <url id="cuh11tlf439618i6ks8g" type="url" status="failed" title="" wc="0">http://arduino.cc/en/Tutorial/ButtonStateChange</url> 

 */

功能：

检测按钮从关闭到打开（或从打开到关闭）的状态变化。

硬件连接：

按钮连接到数字引脚2和+5V。
一个10KΩ的电阻连接到数字引脚2和地（GND）。
一个LED连接到数字引脚13和地（GND），或者使用大多数Arduino板上的内置LED。

2. 变量定义

const int buttonPin = 2;    // the pin that the pushbutton is attached to
const int ledPin = 13;      // the pin that the LED is attached to

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

buttonPin：定义了一个常量buttonPin，值为2，表示按钮连接在数字引脚2上。
ledPin：定义了一个常量ledPin，值为13，表示LED连接在数字引脚13上。
buttonPushCounter：定义了一个变量buttonPushCounter，初始值为0，用于记录按钮按下的次数。
buttonState：定义了一个变量buttonState，用于存储当前按钮的状态。
lastButtonState：定义了一个变量lastButtonState，用于存储上一次按钮的状态。

3. `setup()` 函数

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);
}

setup() 函数在Arduino板复位后只运行一次。
pinMode(buttonPin, INPUT);：设置数字引脚2为输入模式。
pinMode(ledPin, OUTPUT);：设置数字引脚13为输出模式。
Serial.begin(9600);：初始化串行通信，波特率为9600，用于调试和显示按钮按下的次数。

4. `loop()` 函数

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);
  }
}

loop() 函数会不断重复运行。
buttonState = digitalRead(buttonPin);：读取数字引脚2的状态。
if (buttonState != lastButtonState)：检查当前按钮状态是否与上一次状态不同。
如果不同，说明按钮状态发生了变化。
if (buttonState == HIGH)：如果当前状态为HIGH，说明按钮从关闭变为打开。
增加按钮按下的次数buttonPushCounter。
通过串行通信打印“on”和当前按钮按下的次数。
else：如果当前状态为LOW，说明按钮从打开变为关闭。
通过串行通信打印“off”。
delay(50);：延迟50毫秒，以避免按钮抖动。
lastButtonState = buttonState;：将当前状态保存为上一次状态，以便下次循环使用。
if (buttonPushCounter % 4 == 0)：检查按钮按下的次数是否是4的倍数。
如果是4的倍数，点亮LED。
否则，熄灭LED。

硬件连接

按钮连接：

将按钮的一个引脚连接到数字引脚2。
将按钮的另一个引脚连接到+5V。
将一个10KΩ的电阻连接到数字引脚2和地（GND）。

LED连接：

将LED的长脚（正极）连接到数字引脚13。
将LED的短脚（负极）连接到地（GND）。

Arduino板：

确保Arduino板通过USB线连接到电脑。

运行结果

当按下按钮时，按钮按下的次数会增加，并通过串行监视器打印“on”和当前按下的次数。
当松开按钮时，通过串行监视器打印“off”。
每当按钮按下的次数是4的倍数时，LED会点亮；否则，LED会熄灭。

修改建议

调整LED触发条件：可以通过修改if (buttonPushCounter % 4 == 0)中的条件来改变LED的触发频率。例如，将4改为3，LED会在每次按钮按下3次时点亮。
添加消抖功能：如果按钮抖动导致误触发，可以增加更长的延迟时间或使用软件消抖算法。
使用其他引脚：如果需要使用其他引脚作为按钮输入或LED输出，只需将buttonPin和ledPin的值改为对应的引脚号即可。

视频讲解

BiliBili： 视睿网络-哔哩哔哩视频 (bilibili.com)

State change detection 状态变化检测

代码功能

代码逐行解释

1. 注释部分

功能：

硬件连接：

2. 变量定义

3. setup() 函数

4. loop() 函数

硬件连接

按钮连接：

LED连接：

Arduino板：

运行结果

修改建议

视频讲解

3. `setup()` 函数

4. `loop()` 函数