Count 0 to 9 on an Uno

// 0.56" seven-segment digit driven by a 74HC595 driver board.
//
// Wiring (Arduino Uno R3):
//   Uno 5V  -> board VCC
//   Uno GND -> board GND
//   Uno D8  -> board SER     (data)
//   Uno D11 -> board RCLK    (latch)
//   Uno D12 -> board SRCLK   (shift clock)
//   board A B C D E F G H -> digit A B C D E F G H   (H is the decimal point)
//   digit's two common pins -> GND on a 5161AS, 5V on a 5161BS
//
// Arduino IDE: Tools > Board > Arduino AVR Boards > Arduino Uno
//              Tools > Port  > the port that appears when the board is plugged in
// No library needed.

#define COMMON_ANODE 0   // 0 = 5161AS (commons to GND), 1 = 5161BS (commons to 5V)

const int PIN_SER   = 8;    // data
const int PIN_RCLK  = 11;   // latch
const int PIN_SRCLK = 12;   // shift clock

const int stepDelayMs = 500;

// Bit 0 is segment A, bit 7 the decimal point. Written for a common-cathode
// digit: a 1 lights its segment.
const uint8_t kDigits[10] = {
  0b00111111, // 0
  0b00000110, // 1
  0b01011011, // 2
  0b01001111, // 3
  0b01100110, // 4
  0b01101101, // 5
  0b01111101, // 6
  0b00000111, // 7
  0b01111111, // 8
  0b01101111, // 9
};

// A common-anode digit lights a segment when its pin goes LOW, so the same
// table goes out inverted. One place, so there is only one table to maintain.
static uint8_t segOut(uint8_t raw) {
#if COMMON_ANODE
  return (uint8_t)~raw;
#else
  return raw;
#endif
}

// Nothing lit. Not the same byte on the two kinds of digit.
static uint8_t blankPattern() {
#if COMMON_ANODE
  return 0xFF;
#else
  return 0x00;
#endif
}

// Hold the outputs still, shift eight bits in, then show them all at once.
static void shiftWrite(uint8_t data) {
  digitalWrite(PIN_RCLK, LOW);
  shiftOut(PIN_SER, PIN_SRCLK, MSBFIRST, data);
  digitalWrite(PIN_RCLK, HIGH);
}

void setup() {
  pinMode(PIN_SER, OUTPUT);
  pinMode(PIN_RCLK, OUTPUT);
  pinMode(PIN_SRCLK, OUTPUT);

  shiftWrite(blankPattern());   // start blank, not with whatever was in the register
}

void loop() {
  for (int i = 0; i <= 9; i++) {
    shiftWrite(segOut(kDigits[i]));
    delay(stepDelayMs);
  }
}