开关抖动及消除的办法

/* SoftwareDebounce

 * 

 * At each transition from LOW to HIGH or from HIGH to LOW 

 * the input signal is debounced by sampling across

 * multiple reads over several milli seconds.  The input

 * is not considered HIGH or LOW until the input signal 

 * has been sampled for at least "debounce_count" (10)

 * milliseconds in the new state.

 *

 * Notes:

 *   Adjust debounce_count to reflect the timescale 

 *     over which the input signal may bounce before

 *     becoming steady state

 *

 * Based on:

 *   http://www.arduino.cc/en/Tutorial/Debounce

 *

 * Jon Schlueter

 * 30 December 2008

 *

 * http://playground.arduino.cc/Learning/SoftwareDebounce

 */



int inPin = 7;         // the number of the input pin

int outPin = 13;       // the number of the output pin



int counter = 0;       // how many times we have seen new value

int reading;           // the current value read from the input pin

int current_state = LOW;    // the debounced input value



// the following variable is a long because the time, measured in milliseconds,

// will quickly become a bigger number than can be stored in an int.

long time = 0;         // the last time the output pin was sampled

int debounce_count = 10; // number of millis/samples to consider before declaring a debounced input



void setup()

{

  pinMode(inPin, INPUT);

  pinMode(outPin, OUTPUT);

  digitalWrite(outPin, current_state); // setup the Output LED for initial state

}





void loop()

{

  // If we have gone on to the next millisecond

  if(millis() != time)

  {

    reading = digitalRead(inPin);



    if(reading == current_state && counter > 0)

    {

      counter--;

    }

    if(reading != current_state)

    {

       counter++; 

    }

    // If the Input has shown the same value for long enough let's switch it

    if(counter >= debounce_count)

    {

      counter = 0;

      current_state = reading;

      digitalWrite(outPin, current_state);

    }

    time = millis();

  }

}