const int trigPin1 = 5;
const int echoPin1 = 18;
const int trigPin2 = 19;
const int echoPin2 = 21;
const int trigPin3 = 2;
const int echoPin3 = 4;

//define sound speed in cm/uS
#define SOUND_SPEED 0.034

long duration1;
float distanceCm1;
long duration2;
float distanceCm2;
long duration3;
float distanceCm3;

void setup() {
  Serial.begin(115200); // Starts the serial communication
  pinMode(trigPin1, OUTPUT); // Sets the trigPin as an Output
  pinMode(echoPin1, INPUT); // Sets the echoPin as an Input
  pinMode(trigPin2, OUTPUT);
  pinMode(echoPin2, INPUT);
  pinMode(trigPin3, OUTPUT);
  pinMode(echoPin3, INPUT);
}

void loop() {
  // Sensor 1
  // Clears the trigPin
  digitalWrite(trigPin1, LOW);
  delayMicroseconds(2);
  // Sets the trigPin on HIGH state for 10 micro seconds
  digitalWrite(trigPin1, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin1, LOW);
  
  // Reads the echoPin, returns the sound wave travel time in microseconds
  duration1 = pulseIn(echoPin1, HIGH);
  
  // Calculate the distance
  distanceCm1 = duration1 * SOUND_SPEED/2;
  
  // Prints the distance in the Serial Monitor
  Serial.print("Distance 1 (cm): ");
  Serial.println(distanceCm1);
  
  delay(1000);

  // Sensor 2
  // Clears the trigPin
  digitalWrite(trigPin2, LOW);
  delayMicroseconds(2);
  // Sets the trigPin on HIGH state for 10 micro seconds
  digitalWrite(trigPin2, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin2, LOW);
  
  // Reads the echoPin, returns the sound wave travel time in microseconds
  duration2 = pulseIn(echoPin2, HIGH);
  
  // Calculate the distance
  distanceCm2 = duration2 * SOUND_SPEED/2;
  
  // Prints the distance in the Serial Monitor
  Serial.print("Distance 2 (cm): ");
  Serial.println(distanceCm2);
  
  delay(1000);

  // Sensor 3
  // Clears the trigPin
  digitalWrite(trigPin3, LOW);
  delayMicroseconds(2);
  // Sets the trigPin on HIGH state for 10 micro seconds
  digitalWrite(trigPin3, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin3, LOW);
  
  // Reads the echoPin, returns the sound wave travel time in microseconds
  duration3 = pulseIn(echoPin3, HIGH);
  
  // Calculate the distance
  distanceCm3 = duration3 * SOUND_SPEED/2;
  
  // Prints the distance in the Serial Monitor
  Serial.print("Distance 3 (cm): ");
  Serial.println(distanceCm3);
  
  delay(1000);
}