7seg_random.ino

#include <SPI.h>

#define PIN_SCK 13
#define PIN_SDI 11
#define PIN_LATCH 10
#define SCROLL_SPEED 50

const byte digits[] PROGMEM = {
  0b11111100,  // 0
  0b01100000,  // 1
  0b11011010,  // 2
  0b11110010,  // 3
  0b01100110,  // 4
  0b10110110,  // 5
  0b10111110,  // 6
  0b11100000,  // 7
  0b11111110,  // 8
  0b11110110,  // 9
};

void setup() {
  randomSeed(analogRead(0));
  pinMode(PIN_LATCH, OUTPUT);
  SPI.begin();
  SPI.setBitOrder(LSBFIRST);
}

void loop() {
  for (int i = 0; i < 10; i++) {
    digitalWrite(PIN_LATCH, LOW);
    SPI.transfer(pgm_read_byte_near(digits + random(0, 9)));
    digitalWrite(PIN_LATCH, HIGH);
    delay(SCROLL_SPEED * random(1, 10));
  }
}