#define inputCLK 3
 #define inputDT 4
 
 int counter = 0; 
 int currentStateCLK;
 int previousStateCLK; 
 
 
 void setup() { 
   
   pinMode (inputCLK,INPUT);
   pinMode (inputDT,INPUT);
   pinMode(13, OUTPUT);

   Serial.begin (9600);

   previousStateCLK = digitalRead(inputCLK);
 
 } 
 
 void loop() { 
  
   currentStateCLK = digitalRead(inputCLK);   
   if (currentStateCLK != previousStateCLK){       
     if (digitalRead(inputDT) != currentStateCLK) { 
       counter --;
     } else {
       counter ++;      
     }   
     Serial.print(" -- Value: ");
     Serial.println(counter);
   } 
   previousStateCLK = currentStateCLK; 
 }