int s0 = 18;
int s1 = 5;
int s2 = 4;
int s3 = 2;
int SIG1 = 13;

int x0 = 23;
int x1 = 22;
int x2 = 21;
int x3 = 19;
int SIG2 = 12;

void setup(){
  pinMode(18, OUTPUT);
  pinMode(5, OUTPUT);
  pinMode(4, OUTPUT);
  pinMode(2, OUTPUT);
  pinMode(13, OUTPUT);
  pinMode(23, OUTPUT);
  pinMode(22, OUTPUT);
  pinMode(21, OUTPUT);
  pinMode(19, OUTPUT);
}

void loop(){
  int controlPin1[] = {s0, s1, s2, s3};
  int controlPin2[] = {x0, x1, x2, x3};
  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
  };

  for(int j = 0; j < 16; j ++){
    for(int i = 0; i < 4; i ++){
      digitalWrite(controlPin1[i], muxChannel[j][i]);
    }
    analogWrite(SIG1,HIGH);
  }
}