First attempt at Max7219

Max7219.ino

//We always have to include the library
#include "LedControl.h"

// Arduino Pins
int dataPin = 12;
int clockPin = 11;
int loadPin = 10;

LedControl lc = LedControl(dataPin, clockPin, loadPin, 1);

int getNextBlink() {
  return millis() + random(2000, 10000);
}

int getBlinkLength() {
  return random(100, 300);
}

// State
int nextBlink = getNextBlink();
int blinkLength = getBlinkLength();
boolean isBlinking = false;

// Expressions
int forward[4][2] = {
  { 0, B00000000 },
  { 1, B11011101 },
  { 2, B01011101 },
  { 3, B00000000 }
};

int blinking[4][2] = {
  { 0, B00000000 },
  { 1, B10001000 },
  { 2, B00001000 },
  { 3, B00000000 }
};

void writeExpression(int expr[4][2]) {
  for (int i = 0; i < 4; i++) {
    lc.setRow(0, expr[i][0], expr[i][1]);
  }
}

void setup() {
  /*
   The MAX72XX is in power-saving mode on startup,
   we have to do a wakeup call
   */
  lc.shutdown(0, false);
  /* Set the brightness */
  lc.setIntensity(0, 14);
  /* Set the brightness */
  lc.setScanLimit(0, 3);
  /* and clear the display */
  lc.clearDisplay(0);
}

void loop() {
  int now = millis();
  
  if (!isBlinking && now > nextBlink) {
    isBlinking = true;
    writeExpression(blinking);
  }
  
  else if (isBlinking && now > nextBlink + blinkLength) {
    isBlinking = false;
    writeExpression(forward);
    nextBlink = getNextBlink();
    blinkLength = getBlinkLength();
  }
}