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Arduino内置教程-数字-按键消抖

防抖当按下时,按键经常产生错误的开/关变迁,这是机械物理的问题:这些变迁可能被读取为在短时间内多次按下,从而使程序变笨。这个例子示范了怎样使一个输入防抖,这意味着在一个短时间内检查两次来确保这个按键是确实被按下了。如果没有防抖,按一次这个按键可能会引起不可预测的结果。这个程序利用millis()函数来保持按下的时间间隔。

简介

当按下时,按键经常产生错误的开/关变化,这是机械物理的问题:这些变化可能被读取为在短时间内多次按下,从而使程序变笨。这个例子示范了怎样使一个输入防抖,这意味着在一个短时间内检查两次来确保这个按键是确实被按下了。如果没有防抖,按一次这个按键可能会引起不可预测的结果。这个程序利用millis()函数来保持按下的时间间隔。

硬件要求

  • Arduino or Genuino 开发板
  • 即时按键或者开关
  • 10k ohm 电阻
  • 连接线
  • 面包板

电路

Arduino内置教程-数字-防抖

原理图

Arduino内置教程-数字-防抖

样例代码

例子里,当闭合时开关为低电平,而断开时开关未高电平。这里当按下开关时为高电平,没有按下时为低电平。

// constants won't change. They're used here to
// set pin numbers:
const int buttonPin = 2;    // the number of the pushbutton pin
const int ledPin = 13;      // the number of the LED pin

// Variables will change:
int ledState = HIGH;         // the current state of the output pin
int buttonState;             // the current reading from the input pin
int lastButtonState = LOW;   // the previous reading from the input pin

// the following variables are long's because the time, measured in miliseconds,
// will quickly become a bigger number than can be stored in an int.
long lastDebounceTime = 0;  // the last time the output pin was toggled
long debounceDelay = 50;    // the debounce time; increase if the output flickers

void setup() {
  pinMode(buttonPin, INPUT);
  pinMode(ledPin, OUTPUT);

  // set initial LED state
  digitalWrite(ledPin, ledState);
}

void loop() {
  // read the state of the switch into a local variable:
  int reading = digitalRead(buttonPin);

  // check to see if you just pressed the button
  // (i.e. the input went from LOW to HIGH),  and you've waited
  // long enough since the last press to ignore any noise:

  // If the switch changed, due to noise or pressing:
  if (reading != lastButtonState) {
    // reset the debouncing timer
    lastDebounceTime = millis();
  }

  if ((millis() - lastDebounceTime) > debounceDelay) {
    // whatever the reading is at, it's been there for longer
    // than the debounce delay, so take it as the actual current state:

    // if the button state has changed:
    if (reading != buttonState) {
      buttonState = reading;

      // only toggle the LED if the new button state is HIGH
      if (buttonState == HIGH) {
        ledState = !ledState;
      }
    }
  }

  // set the LED:
  digitalWrite(ledPin, ledState);

  // save the reading.  Next time through the loop,
  // it'll be the lastButtonState:
  lastButtonState = reading;
}

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