int volatile pulse = 0;
int volatile angle = 0;
float omega;
int angle_old = 0;
float old_millis = 0;
float dt;

void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);
  pinMode(2, INPUT_PULLUP);
  attachInterrupt(digitalPinToInterrupt(2), encoder, FALLING);
}

void loop() {
  // put your main code here, to run repeatedly:
  Serial.println(angle);
  // dt = millis()-old_millis; 
  // omega = 1000*(angle_old-angle)/dt;
  // angle_old = angle;
  // old_millis = millis();
  // Serial.println(omega);
}

void encoder(){
  if (digitalRead(3)==0){
    pulse+=1;
  }else{
    pulse-=1;
  }
  angle = (pulse % 20)*18;
}