//https://forum.arduino.cc/t/wrong-analogread-values-when-using-cd74hc4067-multiplexer-on-arduino-uno/1261594
//Mux control pins
int s0 = 2;
int s1 = 3;
int s2 = 4;

//Mux in “SIG” pin
int SIG_pin = A0;

void setup(){
pinMode(s0, OUTPUT);
pinMode(s1, OUTPUT);
pinMode(s2, OUTPUT);

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

pinMode(SIG_pin, INPUT);

Serial.begin(9600);
}

void loop(){
  for(int i = 0; i < 8; i ++){ 
    Serial.print("Value at channel "); 
    Serial.print(i); Serial.print("is : "); 
    Serial.println(readMux(i)); 
    delay(500); 
  } 
} 

int readMux(int channel){ 
  int controlPin[] = {s0, s1, s2}; 
  int muxChannel[16][4]={ {0,0,0,0}, 
  {1,0,0,0}, 
  {0,1,0,0}, 
  {1,1,0,0}, 
  {0,0,1,0}, 
  {1,0,1,0}, 
  {0,1,1,0}, 
  {1,1,1,0}, 
  {0,0,0,1}, 
  {1,0,0,1}, 
  {0,1,0,1}, 
  {1,1,0,1}, 
  {0,0,1,1}, 
  {1,0,1,1}, 
  {0,1,1,1}, 
  {1,1,1,1} }; 
  //loop through the 4 sig 
  for(int i = 0; i < 3; i ++){ 
    digitalWrite(controlPin[i], muxChannel[channel][i]); 
    } 
    //read the value at the SIG pin 
    int val = analogRead(SIG_pin); //return the value 
    return val; 
  }