#include <Wire.h>
const int led = 4;
    
void setup() {
  Serial.begin(9600);
  Serial.println("\nI2C Scanner");
  Wire.begin();
  pinMode(led, OUTPUT);
  digitalWrite(led, LOW);  
}

float readUS()
{
  uint32_t data;
  Wire.beginTransmission(0x57); //Transfer data to 0x57.  
  Wire.write(0x01);
  Wire.endTransmission(); //Stop data transmission with the Ultrasonic Unit. Ultrasonic Unit
  delay(20);
  Wire.requestFrom(0x57,3); //Request 3 bytes from Ultrasonic Unit.
  data  = Wire.read();data <<= 8;
  data |= Wire.read();data <<= 8;
  data |= Wire.read();
  return float(data) / 1000;
}

void loop() {
  static float newvalue = 0;
  newvalue = readUS();
    Serial.println(String(newvalue));
    if (newvalue < 100)
    {
      digitalWrite(led, HIGH);
      delay(200);      
    }
    else
    {
      digitalWrite(led, LOW);      
    }    
  delay(200);
}