int s0 = 13;
int s1 = 12;
int s2 = 14;
int s3 = 27;
int inputSignalPin = 26;

int readMux(int channel){
  int controlPin[] = {s0, s1, s2, s3};

  int muxChannel[16][4]={
    {0,0,0,0}, //channel 0
    {1,0,0,0}, //channel 1
    {0,1,0,0}, //channel 2
    {1,1,0,0}, //channel 3
    {0,0,1,0}, //channel 4
    {1,0,1,0}, //channel 5
    {0,1,1,0}, //channel 6
    {1,1,1,0}, //channel 7
    {0,0,0,1}, //channel 8
    {1,0,0,1}, //channel 9
    {0,1,0,1}, //channel 10
    {1,1,0,1}, //channel 11
    {0,0,1,1}, //channel 12
    {1,0,1,1}, //channel 13
    {0,1,1,1}, //channel 14
    {1,1,1,1}  //channel 15
  };

  //loop through the 4 sig
  for(int i = 0; i < 4; i ++){
    digitalWrite(controlPin[i], muxChannel[channel][i]);
  }

  //read the value at the SIG pin
  int val = analogRead(inputSignalPin);

  //return the value
  return val;
}

void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);
  Serial.println("Hello, ESP32!");

  pinMode(s0, OUTPUT); 
  pinMode(s1, OUTPUT); 
  pinMode(s2, OUTPUT); 
  pinMode(s3, OUTPUT); 

  digitalWrite(s0, LOW);
  digitalWrite(s1, LOW);
  digitalWrite(s2, LOW);
  digitalWrite(s3, LOW);
}

void loop() {
  // put your main code here, to run repeatedly:
  for (int i=0;i<16;i++){
    int inputSignal = readMux(i);
    delay(200);
    Serial.print("Channel-");
    Serial.print(i);
    Serial.print(" Value:");
    Serial.println(inputSignal);
  }
  // delay(10); // this speeds up the simulation
}