Arduino LED Matrix Emojis — Heart ❤️ and Smile 😊!

My Arduino UNO R4 WiFi has a built-in 12×8 LED matrix. Today I used it to show two of my favorite emojis:

❤️ Heart 😊 Smiley face

They blink one after another, like a tiny digital locket! 💝

What you need

• Arduino UNO R4 WiFi
• USB cable

Still zero extra components! 🙌

The code

/*
  Arduino UNO R4 WiFi LED Matrix — Heart and Smile
  Shows a heart emoji (❤️) and a smiley face (😊) on the built-in 12x8 LED matrix.
*/

#include "Arduino_LED_Matrix.h"

ArduinoLEDMatrix matrix;

// 8 rows x 12 columns, values: 0 = off, 255 = full brightness
uint8_t frame[8][12];

// Heart shape frame
uint8_t heart[8][12] = {
  {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
  {0, 0, 0, 255, 255, 0, 0, 255, 255, 0, 0, 0},
  {0, 0, 255, 255, 255, 255, 255, 255, 255, 255, 0, 0},
  {0, 0, 255, 255, 255, 255, 255, 255, 255, 255, 0, 0},
  {0, 0, 0, 255, 255, 255, 255, 255, 255, 0, 0, 0},
  {0, 0, 0, 0, 255, 255, 255, 255, 0, 0, 0, 0},
  {0, 0, 0, 0, 0, 255, 255, 0, 0, 0, 0, 0},
  {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
};

// Smiley face frame
uint8_t smiley[8][12] = {
  {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
  {0, 0, 0, 255, 255, 0, 0, 255, 255, 0, 0, 0},
  {0, 0, 0, 255, 255, 0, 0, 255, 255, 0, 0, 0},
  {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
  {0, 0, 255, 0, 0, 0, 0, 0, 0, 255, 0, 0},
  {0, 0, 255, 0, 0, 0, 0, 0, 0, 255, 0, 0},
  {0, 0, 0, 255, 255, 255, 255, 255, 255, 0, 0, 0},
  {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
};

void setup() {
  Serial.begin(9600);
  matrix.begin();
  Serial.println("Heart and Smile LED Matrix started!");
}

void loop() {
  // Show heart for 1.5 seconds
  memcpy(frame, heart, sizeof(heart));
  matrix.loadPixels(&frame[0][0], 8 * 12);
  delay(1500);

  // Show smiley for 1.5 seconds
  memcpy(frame, smiley, sizeof(smiley));
  matrix.loadPixels(&frame[0][0], 8 * 12);
  delay(1500);
}

How I uploaded it

arduino-cli board list
arduino-cli compile --fqbn arduino:renesas_uno:unor4wifi MatrixEmoji
arduino-cli upload -p /dev/cu.usbmodem9888E00970202 --fqbn arduino:renesas_uno:unor4wifi MatrixEmoji

On Windows, your port will look like COM3 or COM4.

How it works

Part	What it does
matrix.begin()	Starts the LED matrix
heart[8][12]	Stores the heart picture as 96 brightness values
smiley[8][12]	Stores the smiley picture as 96 brightness values
memcpy(frame, heart, ...)	Copies the picture into the active frame
matrix.loadPixels(&frame[0][0], 8 * 12)	Sends the picture to the matrix

Try changing it!

• Swap the emojis — show a star ⭐ or music note 🎵
• Make them fade in and out using PWM-style brightness values
• Add a third emoji like a thumbs up 👍
• Make the heart beat faster by changing the delay times

What’s next?

I want to try scrolling text next — maybe my name “NITVI” moving across the matrix! Or maybe a tiny reaction meter that shows different emojis based on sensor input.

See my other LED matrix post:

• Arduino LED Matrix — Smiley Face & Bouncing Dot!