// Define the control pins for the 74HC4067 multiplexer
const int S0 = 11;
const int S1 = 10;
const int S2 = 9;
const int S3 = 8;

// Define the trigger pins for the ultrasonic sensors
const int trigPins[] = {6, 7}; // Adjust according to the number of sensors

// Common I/O pin from the multiplexer connected to an analog input
const int echoPin = A0;

// Number of sensors
const int numSensors = sizeof(trigPins) / sizeof(trigPins[0]);

void setup() {
  Serial.begin(9600);
  
  // Set the control pins as outputs
  pinMode(S0, OUTPUT);
  pinMode(S1, OUTPUT);
  pinMode(S2, OUTPUT);
  pinMode(S3, OUTPUT);
  
  // Set the trigger pins as outputs
  for (int i = 0; i < numSensors; i++) {
    pinMode(trigPins[i], OUTPUT);
  }
  
  // Set the echo pin as input
  pinMode(echoPin, INPUT);
}

void loop() {
  for (int i = 0; i < numSensors; i++) {
    // Select the multiplexer channel
    selectMuxChannel(i);

    // Read distance from the current sensor
    long duration = readUltrasonic(trigPins[i]);
    int distance = duration * 0.034 / 2;

    // Print the distance to the Serial Monitor
    Serial.print("Sensor ");
    Serial.print(i);
    Serial.print(": ");
    Serial.print(distance);
    Serial.println(" cm");
    
    delay(100); // Small delay between readings
  }
}

void selectMuxChannel(int channel) {
  digitalWrite(S0, bitRead(channel, 0));
  digitalWrite(S1, bitRead(channel, 1));
  digitalWrite(S2, bitRead(channel, 2));
  digitalWrite(S3, bitRead(channel, 3));
}

long readUltrasonic(int trigPin) {
  // Set the trigger pin high for 10 microseconds
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  // Read the echo pin
  long duration = pulseIn(echoPin, HIGH);
  
  return duration;
}