https://medium.com/kidstronics/bridging-all-sensors-together-pitbot-ca8803bf9cb

_29_YL70_4_Ch_Line_Tracker_demo_01.ino

/*   Project:  — LEGO Episode # 29
     Bridging All Sensors Together — Pitbot
     Collecting All Codes for the Final Act of Giving Behaviors to Robot

     INO file: _29_YL70_4_Ch_Line_Tracker_demo_01.ino

     date: 9/01/19

    code by: Public Domain
    hardware by: Walfront

    Description: There is no easy way to tell your robot where to go! use this module.

    Visit: https://medium.com/jungletronics

    Tutorial:https://medium.com/kidstronics/bridging-all-sensors-together-pitbot-ca8803bf9cb

    License: CC-SA 3.0, feel free to use this code however you'd like.
    Please improve upon it! Let me know how you've made it better.
*/
void setup()
{
  Serial.begin(9600);
}
void loop()
{
  Serial.print(digitalRead(0));
  Serial.print(" ");
  Serial.print(digitalRead(1));
  Serial.print(" ");
  Serial.print(digitalRead(2));
  Serial.print(" ");
  Serial.println(digitalRead(3));
  delay(500);
}