#include <LedControl.h>
const byte dinPin = 7, clockPin = 5, loadPin = 6;
LedControl display(dinPin, clockPin, loadPin, 1);
const byte ok[8] = {0x00, 0x01, 0x03, 0x86, 0xCC, 0x78, 0x30, 0x00};
const byte attention[8] = {0x18, 0x18, 0x18, 0x18, 0x18, 0x00, 0x18, 0x00};
unsigned long changedAt = 0;
bool showingOk = true;

void draw(const byte *rows) {
  for (byte row = 0; row < 8; ++row) display.setRow(0, row, rows[row]);
}

void setup() {
  display.shutdown(0, false);
  display.setIntensity(0, 1);
  display.clearDisplay(0);
  draw(ok);
}

void loop() {
  if (millis() - changedAt >= 2000) {
    changedAt = millis(); showingOk = !showingOk;
    draw(showingOk ? ok : attention);
  }
}