// Rotary Encoder Inputs
#define CLK 2 // Output A
#define DT 3 // Output B

volatile int currentStateCLK;
volatile int currentStateDT;
bool lastStateCLK;
volatile int counter;
String currentDir ="";

void setup() {
  
  // Set encoder pins as inputs
  attachInterrupt(digitalPinToInterrupt(2),handler, CHANGE);  

  // Setup Serial Monitor
  Serial.begin(9600);

  // Read the initial state of CLK
  lastStateCLK = digitalRead(CLK);
}

void loop() 
{
  if (currentStateCLK != lastStateCLK && currentStateCLK == 1)
  {
    if (digitalRead(DT) != currentStateCLK)
    {
      counter--;
      currentDir = "CCW";
    }
    else
    {
      counter++;
      currentDir = "CW";
    }

    Serial.print("Direction: ");
    Serial.print(currentDir);
    Serial.print(" | Counter: ");
    Serial.println(counter);
  }

}

void handler(void)
{
  currentStateCLK = digitalRead(CLK);
}