Flowing light on a 74HC595 (pins 11, 8 and 12), on an Arduino Uno

// A flowing light: eight LEDs on a 74HC595 fill up one by one.
//
//   74HC595 DS -> pin 11   SH_CP -> pin 8   ST_CP -> pin 12
//   VCC and MR -> 5V   OE and GND -> GND
//   Q0..Q7 -> 220 ohm -> an LED each -> GND
//
// shiftOut() clocks a byte into the chip one bit at a time; the latch pulse
// on ST_CP then puts all eight bits on the outputs at once. Each byte in
// STEPS has one more 1 than the last, so the bar grows from Q0 to Q7.

const int ST_CP = 12;
const int SH_CP = 8;
const int DS = 11;

const byte STEPS[9] = {
  0b00000000, 0b00000001, 0b00000011, 0b00000111, 0b00001111,
  0b00011111, 0b00111111, 0b01111111, 0b11111111,
};

void write595(byte value) {
  digitalWrite(ST_CP, LOW);
  shiftOut(DS, SH_CP, MSBFIRST, value);
  digitalWrite(ST_CP, HIGH);
}

void setup() {
  pinMode(ST_CP, OUTPUT);
  pinMode(SH_CP, OUTPUT);
  pinMode(DS, OUTPUT);
  Serial.begin(9600);
  Serial.println("Mokxi Uno: flowing light on a 74HC595 (DS 11, SH_CP 8, ST_CP 12)");
}

void loop() {
  for (int i = 0; i <= 8; i++) {
    write595(STEPS[i]);
    delay(300);
  }
}