LED bar chaser on an Arduino Uno

// Chaser: eight LEDs, three pins, one 74HC595.
//
// Wiring, shift register to board:
//   DS   (pin 14, serial data)  -> pin 4
//   SHCP (pin 11, shift clock)  -> pin 5
//   STCP (pin 12, latch clock)  -> pin 6
//   MR   (pin 10) to 5 V, OE (pin 13) to GND
//   Q0..Q7 through 220 ohm resistors to eight LEDs to GND
//
// shiftOut with MSBFIRST sends bit 7 first, and the bit sent first ends up
// furthest along the register, so bit n lands on Qn. Q0 is the left-hand LED
// here, which is why a growing bar is (1 << n) - 1 and a running dot is 1 << n.
//
// The latch clock is pulsed only after all eight bits are in, which is the
// whole point of the chip: the outputs sit still while the byte is being
// clocked in and all change together at the end, so nothing flickers through
// the intermediate patterns.

const int DATA_PIN = 4;   // DS
const int SHIFT_PIN = 5;  // SHCP
const int LATCH_PIN = 6;  // STCP

const int BAR_MS = 80;
const int DOT_MS = 70;

static void show(uint8_t bits) {
  shiftOut(DATA_PIN, SHIFT_PIN, MSBFIRST, bits);
  digitalWrite(LATCH_PIN, HIGH);
  digitalWrite(LATCH_PIN, LOW);
}

void setup() {
  pinMode(DATA_PIN, OUTPUT);
  pinMode(SHIFT_PIN, OUTPUT);
  pinMode(LATCH_PIN, OUTPUT);
  digitalWrite(SHIFT_PIN, LOW);
  digitalWrite(LATCH_PIN, LOW);
  Serial.begin(115200);
  Serial.println("Mokxi Arduino Uno: eight LEDs on three pins");
}

void loop() {
  // the bar fills from the left, then empties
  for (int n = 1; n <= 8; n++) {
    show((uint8_t)((1u << n) - 1u));
    delay(BAR_MS);
  }
  for (int n = 7; n >= 0; n--) {
    show((uint8_t)((1u << n) - 1u));
    delay(BAR_MS);
  }
  // then a single dot runs to the right and back
  for (int n = 0; n < 8; n++) {
    show((uint8_t)(1u << n));
    delay(DOT_MS);
  }
  for (int n = 6; n >= 1; n--) {
    show((uint8_t)(1u << n));
    delay(DOT_MS);
  }
}