code

const int I = 2;
const int O = 13;
int ticks = 0;
const int maxTicks = 60;
double pos = 0.0;
bool lock = false;
void setup() {
  Serial.begin(9600);
  pinMode(I, INPUT);
  pinMode(O, OUTPUT);
}
void loop() {
  if(!digitalRead(I)){
    digitalWrite(O, HIGH);
    if(!lock){
      ticks++;
      lock = true;
    }
  }else{
    digitalWrite(O, LOW);
    lock = false;
  }
  pos = ((double)ticks/maxTicks) * 2 * PI;
  Serial.print(ticks);
  Serial.print(" ");
  Serial.println(pos);
}