int potpin = 25;
int val;

#define COM 27
#define Ap 18  // A+ line
#define Am 19  // A- line
#define Bp 5   //  .
#define Bm 17   
int count = 0;
int I=0;

const uint8_t controlPins[] = { 23, 22, 21, 15 };

int readMux(int channel)
{
  for(int i = 0; i < 4; i ++)
  {
    digitalWrite(controlPins[i], channel >> i & 1);
  }
  return digitalRead(COM);
  delay(1);
}



void setup() {
  Serial.begin(115200);
  pinMode(2, INPUT_PULLUP);
  pinMode(16, INPUT_PULLUP);
  pinMode(4, OUTPUT);
  pinMode(Ap,OUTPUT);  pinMode(Am,OUTPUT);
  pinMode(Bp,OUTPUT);  pinMode(Bm,OUTPUT);
  pinMode(COM, INPUT);
  for (int i = 0; i < 4; ++i)
  {
    pinMode(controlPins[i], OUTPUT);
  }
}

void loop() {
  digitalWrite(4,digitalRead(2));
  val = analogRead(potpin);
  //Serial.print(val);
  int analogValue = analogRead(27);
  //Serial.print(analogValue);
  for(int i = 0; i < 16; ++i)
  {
    if (readMux(i))
    {
      Serial.print(analogValue);
    }
    delay(1);
  }
  if ( I++ <(count+=2) and (digitalRead(16)==1) ) {  // stop after 25*4 steps (=100) - quarter turn with gearRatio "2:1"
    delay(4095/val+1);
    digitalWrite(Bm,LOW) ;  digitalWrite(Ap,HIGH);
    delay(4095/val+1);
    digitalWrite(Ap,LOW) ;  digitalWrite(Bp,HIGH);
    delay(4095/val+1);
    digitalWrite(Bp,LOW) ;  digitalWrite(Am,HIGH);
    delay(4095/val+1);
    digitalWrite(Am,LOW) ;  digitalWrite(Bm,HIGH);
  } //else while(1); 
  delay(5);
}