// https://www.idogendel.com/en/archives/211
const byte SER_PIN = 7;
const byte SRCLK_PIN = 8;

void setup() {
  pinMode(SER_PIN, OUTPUT);
  pinMode(SRCLK_PIN, OUTPUT);
}

void loop() {

  digitalWrite(SRCLK_PIN, LOW);
  digitalWrite(SER_PIN, random(2));
  digitalWrite(SRCLK_PIN, HIGH);  
  delay(200);

}