const int sensorPin = A0;
const long referenceMv = 5000;

void setup() {
  Serial.begin(9600);
  pinMode(ledPin, OUTPUT);
}

void loop() {
  //reading the voltage
  int val = analogRead(sensorPin);
  int mV = (val * referenceMv) / 1023;
  int cm = getDistance(mV);

  
  //display values on the screen
  Serial.print(mV);
  Serial.print(",");
  Serial.println(cm);

  delay(1000);
}

//interpolation of distance at 250mV intervals
const int TABLE_ENTRIES = 12;
const int INTERVAL  = 250;
static int distance[TABLE_ENTRIES] = {150,140,130,100,60,50,40,35,30,25,20,15};

int getDistance(int mV) {
  if (mV > INTERVAL * TABLE_ENTRIES - 1)      return distance[TABLE_ENTRIES - 1];
  else {
    int index = mV / INTERVAL;
    float frac = (mV % 250) / (float)INTERVAL;
    return distance[index] - ((distance[index] - distance[index + 1]) * frac);
  }
}