LED Matrix WebServer

Overview

The LED Matrix WebServer system is a fully configurable LED display solution for home networks. It is based on the NodeMCU-32S ESP32 with up to 12 cascaded MAX7219 8x8 LED modules. Using a simple REST API, messages can be displayed, animations controlled, and sensor data queried. Six units are deployed across the apartment, each serving as an information display in its room.

🎯 Easy to use

Web-based control

Control your LED matrix via HTTP REST API from anywhere in the network

🌐 WiFi integrated

Fritz!Box Mesh compatible

Automatic WiFi connection and reconnect

📡 OTA updates

Update firmware wirelessly

Update your firmware without a USB connection

🌡️ Sensors

DHT22 integrated

Read temperature and humidity

🔊 Buzzer sounds

Tone sequences

Predefined melodies for alarms and notifications

📦 Extensible

Analog inputs

GPIO 34/35/36 available for external sensors

Use Cases

The LED Matrix is a receiver — what you send to it is entirely up to you. Here are some examples of how I use the displays across the apartment.

🕐

Date & Time

Always-on clock and date display in each room

🌤️

Weather Data

Current temperature and conditions from indoor sensors

📊

Sensor Readings

Live temperature and humidity from the on-board DHT22 sensor, stored in InfluxDB via MQTT

🔔

Status Messages

Notifications like "washing machine done" triggered via MQTT and Tasmota energy monitoring

🌐

Custom Messages

Any text or scrolling message via the REST API

Installation

Six LED Matrix units are deployed across the apartment, each mounted in its respective room. Every unit consists of an ESP32 board with cascaded MAX7219 LED modules and a DHT22 sensor, connected via SPI. The displays are powered through micro-USB or directly via the 5V pins.

Red Installation

LED Matrix with red backlight on iMac

AnyCubic Printer Setup

LED Matrix installation above 3D printer

Green-yellow Installation

LED Matrix with green/yellow LED configuration

Green Close-up

Detailed view of a green LED Matrix with wiring

Blue Installation

LED Matrix with blue brightness
Many pixels defective

Cyan Installation

Multiple modules with cyan-colored lighting
Some pixels defective

Feature Overview

📱

REST API

HTTP-based control of all functions from anywhere in the network

🎬

Animations

MD_Parola Library with various scroll modes

💾

EEPROM Storage

Persistently save and load messages

🔄

Asynchronous Web Engine

Non-blocking AsyncWebServer for reliable performance

🌡️

Sensor Integration

DHT22 read every 60 seconds

🔊

Sounds & Alarms

4 predefined melodies: Error, Done, Warning, Completed

Hardware Components

Component	Model / Type	Features
Microcontroller	NodeMCU-32S ESP32	32-Bit Dual-Core 240MHz, WiFi + Bluetooth
LED Display	12× MAX7219 8x8 Module	cascaded
Sensor	DHT22 (AM2302)	Temperature ±0.5°C, Humidity ±2%
Buzzer	Passive Buzzer	GPIO 16 PWM controlled via NPN transistor
Power Supply	Micro USB or direct 5V pin	5V for MAX7219, 3.3V internal for logic

Pin Configuration

GPIO Pin Assignment

LedMatrix Software V1.08
NodeMCU-32S ESP32 (USB powered)

POWER SUPPLY:
  Micro USB ──→ ESP32 (5V regulator generates 3.3V internal)
  or: 5V Pin ──→ ESP32 5V (bypassing USB regulator)

SPI SIGNALS (MAX7219):
  VIN 5V  ──→ MAX7219 VCC
  GND     ──→ MAX7219 GND
  GPIO 5  ──→ MAX7219 CS  (Chip Select)
  GPIO 18 ──→ MAX7219 CLK (Clock)
  GPIO 23 ──→ MAX7219 DIN (Data In)
  Modul 1 DOUT → Modul 2 DIN → Modul 3 DIN

DHT22 SENSOR:
  GPIO 27 ──→ DHT22 Data
  3V3    ──→ DHT22 VCC
  GND     ──→ DHT22 GND

BUZZER:
  GPIO 16 ──→ Buzzer Control (via transistor)
  GPIO 16 ──1kΩ── NPN Transistor BASE
                    NPN Transistor COLLECTOR ──→ Buzzer +
                    NPN Transistor EMITTER ──→ GND
  Buzzer - ──→ GND (ESP32)

ANALOG INPUTS (optional):
  GPIO 34 ──→ Analog Sensor 1
  GPIO 35 ──→ Analog Sensor 2
  GPIO 36 ──→ Analog Sensor 3

REST API Documentation

All endpoints are accessible via HTTP. The LED Matrix is recognized as ledmatrix.fritz.box in the network.

Base Endpoints

Welcome Page HTML

GET /
Response: HTML Welcome Page with menu

Firmware Version

GET /version
Response: v1.08 (dht)

Message & Display

Display message (static)

GET /print?text=Hallo%20Welt
Displays a static message on the LED matrix (max 75 characters)

Message with scroll animation

GET /scroll?text=Scrolling%20Text
Text scrolls from left to right across the matrix
Switches back to the last print message afterwards

Test display

GET /test
Displays "Hello world" on the LED matrix

Change LED brightness

GET /set?intensity=8
Value: 0 (dark) to 15 (bright)

Turn off display

GET /off
Turns off the LED matrix (power saving)

Sensor Data

Read temperature

GET /temperature
Response: "23.5" (degrees Celsius)

Read humidity

GET /humidity
Response: "65.2" (percent relative humidity)

Read analog inputs

GET /analog34
GET /analog35
GET /analog36
Response: Value between 0-4095

GET /analogvalues
Response: "1234,2345,3456" (comma-separated values)

Sounds & Buzzer

Done melody

GET /sound/erledigt
Plays positive tone sequence

Warning melody

GET /sound/warnung
Plays warning tone sequence

Error melody

GET /sound/fehler
Plays error tone sequence

Completed melody

GET /sound/abgeschlossen
Plays completed tone sequence

Control & System

Restart system

GET /restart
ESP32 will be restarted (with display shutdown)

curl Examples

curl: display text

curl "http://ledmatrix.fritz.box/print?text=Hallo%20Welt"

curl: text with scroll

curl "http://ledmatrix.fritz.box/scroll?text=Breaking%20News"

curl: read temperature

curl "http://ledmatrix.fritz.box/temperature"

curl: play sound

curl "http://ledmatrix.fritz.box/sound/erledigt"

curl: set brightness

curl "http://ledmatrix.fritz.box/set?intensity=10"

Technical Specifications

Property	Value	Notes
Firmware Version	v1.08 (DHT)	January 2026
Power Supply	Micro USB 5V or direct 5V pin	~500mA for logic
WiFi Standard	802.11 b/g/n	2.4GHz
LED Display	12× 8x8 Module (96×8 Pixel)
DHT22 Range	-40°C to +80°C	Humidity 0-100% RH
Update Method	OTA (AsyncElegantOTA)	Wireless via HTTP
DHT22 Update Interval	60 seconds	Minimum read interval
Message Buffer	75 characters	Max. length of a message