void setup() {
  // put your setup code here, to run once:
Serial.begin(9600);
for (int i=4;i<=7;i++){
  pinMode(i,OUTPUT);
  }
}

int quotient = 0;
int x = 0;


void loop(){
  function2();
  encode();
  Serial.println(analogRead(A0));

  }

void function1() {
  // put your main code here, to run repeatedly:
  x=16*millis()/500;
  quotient=x%16;
}

void function2(){
  x=millis()/1000;
  if (x%2==0)
    quotient=15*(millis()%1000)/1000;

  else
    quotient = 15-15*((millis()%1000))/1000;


  }

void encode(){
  for (int i=4;i<=7;i++){
    digitalWrite(i,quotient%2);
    quotient=quotient/2;
    }

  }