#define CLK 13
#define DIN 11
#define CS  10
#define X_SEGMENTS   4
#define Y_SEGMENTS   4
#define NUM_SEGMENTS (X_SEGMENTS * Y_SEGMENTS)

// Framebuffer for the LED matrix
byte fb[8 * NUM_SEGMENTS];

// Pixel data for a 32x32 Rizz Face
const uint8_t rizzFace[32][4] = {
  {0b00000000, 0b00000000, 0b00000000, 0b00000000}, // Row 1
  {0b00000000, 0b00011110, 0b01111000, 0b00000000}, // Row 2
  {0b00000000, 0b00111111, 0b11111100, 0b00000000}, // Row 3
  {0b00000000, 0b01111111, 0b11111110, 0b00000000}, // Row 4
  {0b00000000, 0b01111100, 0b00111110, 0b00000000}, // Row 5
  {0b00000000, 0b01111100, 0b00111110, 0b00000000}, // Row 6
  {0b00000000, 0b01111000, 0b00011110, 0b00000000}, // Row 7
  {0b00000000, 0b01110000, 0b00001110, 0b00000000}, // Row 8
  {0b00000000, 0b01110000, 0b00001110, 0b00000000}, // Row 9
  {0b00000000, 0b01111000, 0b00011110, 0b00000000}, // Row 10
  {0b00000000, 0b00111100, 0b00111100, 0b00000000}, // Row 11
  {0b00000000, 0b00111110, 0b01111100, 0b00000000}, // Row 12
  {0b00000000, 0b00011111, 0b11111100, 0b00000000}, // Row 13
  {0b00000000, 0b00001111, 0b11111000, 0b00000000}, // Row 14
  {0b00000000, 0b00000111, 0b11110000, 0b00000000}, // Row 15
  {0b00000000, 0b00000011, 0b11100000, 0b00000000}, // Row 16
  {0b00000000, 0b00000001, 0b11000000, 0b00000000}, // Row 17
  {0b00000000, 0b00000001, 0b11000000, 0b00000000}, // Row 18
  {0b00000000, 0b00000011, 0b11100000, 0b00000000}, // Row 19
  {0b00000000, 0b00000111, 0b11110000, 0b00000000}, // Row 20
  {0b00000000, 0b00001111, 0b11111000, 0b00000000}, // Row 21
  {0b00000000, 0b00011111, 0b11111100, 0b00000000}, // Row 22
  {0b00000000, 0b00111110, 0b01111110, 0b00000000}, // Row 23
  {0b00000000, 0b01111100, 0b00111110, 0b00000000}, // Row 24
  {0b00000000, 0b01111000, 0b00011110, 0b00000000}, // Row 25
  {0b00000000, 0b01110000, 0b00001110, 0b00000000}, // Row 26
  {0b00000000, 0b01110000, 0b00001110, 0b00000000}, // Row 27
  {0b00000000, 0b01111000, 0b00011110, 0b00000000}, // Row 28
  {0b00000000, 0b00111100, 0b00111100, 0b00000000}, // Row 29
  {0b00000000, 0b00011110, 0b01111000, 0b00000000}, // Row 30
  {0b00000000, 0b00001111, 0b11110000, 0b00000000}, // Row 31
  {0b00000000, 0b00000000, 0b00000000, 0b00000000}  // Row 32
};

void shiftAll(byte send_to_address, byte send_this_data) {
  digitalWrite(CS, LOW);
  for (int i = 0; i < NUM_SEGMENTS; i++) {
    shiftOut(DIN, CLK, MSBFIRST, send_to_address);
    shiftOut(DIN, CLK, MSBFIRST, send_this_data);
  }
  digitalWrite(CS, HIGH);
}

void setup() {
  pinMode(CLK, OUTPUT);
  pinMode(DIN, OUTPUT);
  pinMode(CS, OUTPUT);

  shiftAll(0x0f, 0x00); // Display test register - test mode off
  shiftAll(0x0b, 0x07); // Scan limit register - display digits 0 to 7
  shiftAll(0x0c, 0x01); // Shutdown register - normal operation
  shiftAll(0x0a, 0x08); // Intensity register - medium brightness
  shiftAll(0x09, 0x00); // Decode mode register - no decode
}

void loop() {
  displayRizzFace();
  delay(500);
}

void displayRizzFace() {
  for (int row = 0; row < 32; row++) {
    for (int segment = 0; segment < X_SEGMENTS; segment++) {
      byte data = rizzFace[row][segment];
      digitalWrite(CS, LOW);
      for (int i = 0; i < NUM_SEGMENTS; i++) {
        if (i / X_SEGMENTS == row / 8 && i % X_SEGMENTS == segment) {
          shiftOut(DIN, CLK, MSBFIRST, row % 8 + 1);
          shiftOut(DIN, CLK, MSBFIRST, data);
        } else {
          shiftOut(DIN, CLK, MSBFIRST, 0);
          shiftOut(DIN, CLK, MSBFIRST, 0);
        }
      }
      digitalWrite(CS, HIGH);
    }
  }
}