Rotary Encoder KY-040 from China - Sample Code

rotary.encoder.KY-040.cpp

long virtualPosition=0; 

#define PinCLK 2                   // Used for generating interrupts using CLK signal
#define PinDT 3                    // Used for reading DT signal
#define PinSW 4                    // Used for the push button switc

void isr ()  {
  noInterrupts();
  if (digitalRead(PinCLK) == digitalRead(PinDT))
     virtualPosition++;
  else
     virtualPosition--;
  Serial.print ("Count = ");  
  Serial.println (virtualPosition);
  interrupts();
}

void setup ()  {
 pinMode(PinCLK,INPUT);
 pinMode(PinDT,INPUT);  
 pinMode(PinSW,INPUT);
 attachInterrupt (0,isr,CHANGE);  // interrupt 0 is always connected to pin 2 on Arduino UNO
 Serial.begin (9600);
 Serial.println("Start");
}

void loop ()  {

}

TERMINAL OUTPUT:
Start
Count = 1
Count = 2
Count = 3
Count = 4
Count = 5
Count = 6
Count = 5
Count = 6
Count = 7
Count = 8
Count = 9
Count = 10

This code will double-count each detent. You should only use one edge of CLK, not both.