Encoders & Resolvers

// Rotary Encoder Inputs
 #define CLK 2  // Use interrupt pin
 #define DT 3
 
 volatile int counter = 0;
 int currentStateCLK;
 int lastStateCLK;
 String currentDir ="";
 
 void setup() {
   pinMode(CLK,INPUT);
   pinMode(DT,INPUT);
   Serial.begin(9600);
   lastStateCLK = digitalRead(CLK);
   
   // Attach interrupt for high speed reading
   attachInterrupt(digitalPinToInterrupt(CLK), updateEncoder, CHANGE);
   attachInterrupt(digitalPinToInterrupt(DT), updateEncoder, CHANGE);
 }
 
 void loop() {
   // Main loop is free to do other things!
   Serial.print("Position: ");
   Serial.println(counter);
   delay(100);
 }
 
 void updateEncoder(){
   currentStateCLK = digitalRead(CLK);
   // If the state has changed -> Pulse occurred
   if (currentStateCLK != lastStateCLK  && currentStateCLK == 1){
     // If the DT state looks different than the CLK state then
     // the encoder is rotating CCW so decrement
     if (digitalRead(DT) != currentStateCLK) {
       counter --;
     } else {
       counter ++;
     }
   }
   lastStateCLK = currentStateCLK;
 }