#define trig 3
#define echo 2

void setup() {
  // put your setup code here, to run once:
Serial.begin(115200);
pinMode(LED_BUILTIN, OUTPUT);
pinMode(trig, OUTPUT);
pinMode(echo, INPUT);
}

float readDistanceCM(){

digitalWrite(trig, LOW);
delayMicroseconds(2);
digitalWrite(trig, HIGH);
delayMicroseconds(10);
digitalWrite(trig, LOW);
int duration = pulseIn(echo, HIGH);
return duration * 0.034 / 2   ;

}
void loop() {
  // put your main code here, to run repeatedly:

float distance = readDistanceCM();

bool isNearby = distance < 100;
  digitalWrite(LED_BUILTIN, isNearby);

Serial.print("Measured Distance: ");
Serial.println(readDistanceCM());

delay(100);



}