const int trigP=23;
const int echoP=21;
long duration;
int distance;
void setup() {
  pinMode(trigP, OUTPUT);
  pinMode(echoP, INPUT);
  Serial.begin(9600);

}

void loop() {
  digitalWrite(trigP, LOW);
  delayMicroseconds(2);
  digitalWrite(trigP, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigP, LOW);
  duration = pulseIn(echoP,HIGH);
  distance = duration*0.034/2;
  Serial.print("Distance=");
  Serial.print(distance);
  delay(500);

}