#define CLK 3
#define DAT 4
#define WAIT 5

void setup()
{
  pinMode(CLK, OUTPUT);
  pinMode(DAT, OUTPUT);
  digitalWrite(CLK, HIGH);
  delay(200);
}

void loop()
{
  for(int i=0; i<256; i++)
  {
    sendByte(i);
    delay(200);
  }
}

void sendByte(uint8_t bt)
{
  digitalWrite(CLK, LOW); //スタートビット
  delay(WAIT);
  digitalWrite(CLK, HIGH);
  delay(WAIT);

  for(int n = 0; n < 8; n++)
  {
    digitalWrite(DAT, (bt >> n) & 1);
    delay(WAIT);
    digitalWrite(CLK, LOW);
    delay(WAIT);
    digitalWrite(CLK, HIGH);
  }
}