#include <Stepper.h>

const int X27StepsPerRevolution = 720;
const int maxSteps = 630; // X27 can only turn 315° => 720 steps * 315° / 360° = 630 steps
int currentPos = 0;

Stepper LSTGauge(X27StepsPerRevolution, 4, 5, 6, 7); // Stepper wired to Arduino pins 4, 5, 6, 7

void setup() {
  Serial.begin(9600);
  LSTGauge.setSpeed(70);

}

void loop() {
  int receivedNb;
  boolean moveOrder = false;
  if (Serial.available()>0) {
    receivedNb = Serial.parseInt();
    while (Serial.available()>0) Serial.read();
    moveOrder = true;
    Serial.print ("Received ");
    Serial.print (receivedNb, DEC);
    Serial.print (" => ");
  }
  if (moveOrder) {
    if (receivedNb == -1) {
      Serial.println ("Homing gauge ...");
      delay(1000);
      LSTGauge.step (-1 * (maxSteps+10));
      currentPos = 0;
    }
    else if (receivedNb >= 0 and receivedNb <= maxSteps) {
      Serial.println ("Moving to " + String(receivedNb) + " steps ... ");
      int relativePos = receivedNb - currentPos;
      Serial.print ("relativePos = "); Serial.println (relativePos);
      Serial.println();
      delay(1000);
      LSTGauge.step (relativePos);
      currentPos = receivedNb;
    }
    else Serial.println ("Nothing to do !");
  }
}