MAX7219 8x8 matrix (pins 12, 10 and 11), on an Arduino Uno

// An 8x8 LED matrix on a MAX7219: three faces, one after another.
//
//   MAX7219 DIN -> pin 12    CLK -> pin 10    CS -> pin 11
//   MAX7219 VCC -> 5V        GND -> GND
//
// Sixty-four LEDs would need sixty-four pins driven directly. The MAX7219
// scans the rows itself; the Uno only sends it one byte per row over three
// wires. LedControl does the sending. Its constructor takes DIN, CLK, CS and
// the number of modules chained together.
//
// Each picture is eight bytes, one per row, with the leftmost LED in the top
// bit. Draw your own on squared paper and type it in.

#include <LedControl.h>

LedControl lc = LedControl(12, 10, 11, 1);

const byte SMILE[8] = {0x3C, 0x42, 0xA5, 0x81, 0xA5, 0x99, 0x42, 0x3C};
const byte FROWN[8] = {0x3C, 0x42, 0xA5, 0x81, 0x99, 0xA5, 0x42, 0x3C};
const byte HEART[8] = {0x00, 0x66, 0xFF, 0xFF, 0xFF, 0x7E, 0x3C, 0x18};

void draw(const byte *picture, const char *name) {
  for (int row = 0; row < 8; row++) lc.setRow(0, row, picture[row]);
  Serial.println(name);
}

void setup() {
  lc.shutdown(0, false);  // the module starts asleep
  lc.setIntensity(0, 8);  // 0 to 15
  lc.clearDisplay(0);
  Serial.begin(9600);
  Serial.println("Mokxi Uno: MAX7219 on pins 12 (DIN), 10 (CLK) and 11 (CS)");
}

void loop() {
  draw(SMILE, "smile");
  delay(1000);
  draw(FROWN, "frown");
  delay(1000);
  draw(HEART, "heart");
  delay(1000);
}