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WiFi LED Matrix Billboard

Schematik

Published June 21, 2026 · Updated July 18, 2026

ESP32Beginner45 minutes2 components5 assembly steps
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Photo of WiFi LED Matrix Billboard

Build a WiFi-controlled LED matrix billboard that displays scrolling text and animations. The ESP32 microcontroller connects to a four-module MAX7219 LED matrix display via a 74AHCT125 logic buffer, which safely translates the ESP32's 3.3V signals to the 5V logic levels the matrix requires. The guide includes a complete wiring diagram, parts list, and step-by-step assembly instructions for connecting power, ground, and the three SPI signal lines.

The included firmware turns the billboard into a web server that broadcasts its own WiFi network. Connect any device to the network, open a browser, and send custom messages with adjustable text effects (scroll, wipe, slice, open, close), brightness levels, and animation speeds. Perfect for signs, notifications, or creative displays that respond to network commands.

Wiring diagram

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Wiring diagram for WiFi LED Matrix Billboard

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Parts list

Bill of materials
ComponentQtyNotes
MAX7219 LED Matrix Display4 × FC-16 chained modules (32 × 8)1Serial LED matrix / 7-segment display driver IC module. Drives one 8x8 LED matrix or up to eight 7-segment digits. Cascadable for multi-digit or multi-matrix displays. Uses a 5V supply with segment current set by an external RSET resistor. Communicates with DIN, CLK, and LOAD/CS; when powered at 5V the datasheet logic-high threshold is 3.5V, so use level shifting for strict 3.3V hosts.
74AHCT125 Quad Buffer / Level ShifterSN74AHCT125N or 74AHCT125 breakout1Quad non-inverting buffer/line driver with 3-state outputs and active-low output-enable pins. In 5 V AHCT/HCT designs, 3.3 V MCU outputs are high enough for the TTL-level inputs, making it a common one-way 3.3 V to 5 V level shifter for WS2812/NeoPixel data and other fast digital lines.

Assembly

5 steps

  1. Arrange the compact billboard

    Place the four FC-16 modules edge-to-edge in their factory daisy-chain order, with the input connector (marked DIN, CLK, CS/LOAD, VCC, GND) facing the ESP32-S2 Mini. Treat the whole chain as one 32×8 display; do not connect to a DOUT connector.

    • Tip: Keep the display’s IN end accessible: DIN must enter the first module, not the far end.
    • Tip: A small stand or enclosure may hold the 32×8 strip; no breadboard is required.

  2. Make the shared 5 V power and ground connections

    Plug USB-C into the LOLIN/WEMOS S2 Mini. Run its 5V/VIN pin to FC-16 VCC and to the 74AHCT125 VCC. Run the S2 Mini GND pin to FC-16 GND and to 74AHCT125 GND.

    • Tip: Use short, reasonably thick power leads for the matrix.
    • Tip: This is a common-ground circuit: the ESP32-S2 Mini, the 74AHCT125, and the FC-16 must all share GND.
    • ⚠ Do not connect the FC-16 VCC to the ESP32 3V3 pin. The FC-16/MAX7219 display is a 5 V load.
    • ⚠ Use a USB supply capable of at least 1 A for reliable bright operation.

  3. Enable the logic buffer

    Tie 1OE, 2OE, and 3OE of the 74AHCT125 to GND. Leave the unused fourth buffer disconnected (or follow the breakout board’s unused-channel guidance).

    • Tip: OE means output enable; on this chip it is active-low, so ground keeps each used channel enabled.
    • ⚠ Do not leave the three used OE inputs floating.

  4. Wire the three billboard signals

    Connect ESP32-S2 GPIO11 (MOSI) to 74AHCT125 1A, then 1Y to FC-16 DIN. Connect GPIO7 (SCK) to 2A, then 2Y to FC-16 CLK. Connect GPIO12 (SS) to 3A, then 3Y to FC-16 CS/LOAD.

    • Tip: Keep each signal label consistent along its two wire segments: GPIO11/MOSI → DIN, GPIO7/SCK → CLK, and GPIO12/SS → CS/LOAD.
    • Tip: The 74AHCT125 is non-inverting, so it preserves all signal meanings while changing 3.3 V logic to 5 V logic.
    • ⚠ Connect DIN only at the matrix chain’s IN end. Reversing the chain will prevent correct text display.

  5. Power and use the WiFi billboard

    With the wiring checked, power the S2 Mini through USB-C. The firmware creates the S2-Billboard WiFi access point and hosts its text, brightness, scroll-speed, and effect controls at 192.168.4.1.

    • Tip: Use Schematik’s Deploy button to compile and flash the firmware.
    • Tip: The default WiFi password is billboard.
    • ⚠ Disconnect USB-C power before changing wiring.

Pin assignments

Board wiring reference
PinConnectionType
5Vmatrix_32x8 VCCpower
GNDmatrix_32x8 GNDground
5Vlogic_buffer VCCpower
GNDlogic_buffer GNDground
GPIO 11logic_buffer 1Adigital
EXTlogic_buffer 1Y → MAX7219 LED Matrix Display DINdigital
GNDlogic_buffer 1OEground
GPIO 7logic_buffer 2Adigital
EXTlogic_buffer 2Y → MAX7219 LED Matrix Display CLKdigital
GNDlogic_buffer 2OEground
GPIO 12logic_buffer 3Adigital
EXTlogic_buffer 3Y → MAX7219 LED Matrix Display CSdigital
GNDlogic_buffer 3OEground

Firmware

ESP32
firmware.cppDeploy to device
#include <Arduino.h>
#include <WiFi.h>
#include <WebServer.h>
#include <SPI.h>
#include <MD_Parola.h>
#include <MD_MAX72xx.h>

// FC-16 4-module matrix: ESP32-S2 -> 74AHCT125 -> matrix input.
#define MOSI_PIN 11
#define SCK_PIN 7
#define CS_PIN 12
#define MAX_DEVICES 4
#define HARDWARE_TYPE MD_MAX72XX::FC16_HW


// Hoisted type definitions
typedef textEffect_t TextEffect;


// Forward declarations
TextEffect selectedEffect();
String htmlEscape(const String &input);
void startAnimation();
void handleRoot();
void handleSet();

const char *AP_SSID = "S2-Billboard";
const char *AP_PASSWORD = "billboard";

MD_Parola matrix = MD_Parola(HARDWARE_TYPE, CS_PIN, MAX_DEVICES);
WebServer server(80);

String message = "HELLO!";
uint8_t brightness = 4;
uint16_t scrollSpeed = 45;
String effectName = "scroll";



TextEffect selectedEffect()
{
  if (effectName == "wipe") return PA_WIPE;
  if (effectName == "slice") return PA_SLICE;
  if (effectName == "open") return PA_OPENING;
  if (effectName == "close") return PA_CLOSING;
  return PA_SCROLL_LEFT;
}

String htmlEscape(const String &input)
{
  String result;
  for (size_t i = 0; i < input.length(); ++i)
  {
    char c = input[i];
    if (c == '&') result += "&amp;";
    else if (c == '<') result += "&lt;";
    else if (c == '>') result += "&gt;";
    else if (c == '"') result += "&quot;";
    else result += c;
  }
  return result;
}

void startAnimation()
{
  matrix.displayClear();
  matrix.setIntensity(brightness);
  matrix.displayText(message.c_str(), PA_CENTER, scrollSpeed, 0, selectedEffect(), selectedEffect());
  matrix.displayReset();
}

void handleRoot()
{
  String page = F("<!doctype html><html><head><meta name='viewport' content='width=device-width,initial-scale=1'>"
                  "<style>body{font-family:Arial,sans-serif;max-width:520px;margin:28px auto;padding:0 16px;background:#101318;color:#f4f7fb}"
                  "h1{font-size:1.45rem}label{display:block;margin-top:16px}input,select,button{box-sizing:border-box;width:100%;padding:11px;margin-top:6px;border-radius:7px;border:1px solid #52606f;font-size:1rem}button{background:#35b778;color:#07150e;border:0;font-weight:bold}.hint{color:#b6c3d1;font-size:.9rem}</style></head><body>"
                  "<h1>32x8 WiFi Billboard</h1><p class='hint'>Connected to the S2-Billboard access point. Changes apply immediately.</p>"
                  "<form action='/set' method='get'><label>Text<input name='text' maxlength='80' value='");
  page += htmlEscape(message);
  page += F("'></label><label>Brightness (0 = dim, 15 = brightest)<input name='brightness' type='number' min='0' max='15' value='");
  page += String(brightness);
  page += F("'></label><label>Scroll speed (milliseconds; lower is faster)<input name='speed' type='number' min='10' max='250' value='");
  page += String(scrollSpeed);
  page += F("'></label><label>Effect<select name='effect'>");
  const char *effects[] = {"scroll", "wipe", "slice", "open", "close"};
  for (const char *effect : effects)
  {
    page += "<option value='" + String(effect) + "'";
    if (effectName == effect) page += " selected";
    page += ">" + String(effect) + "</option>";
  }
  page += F("</select></label><button type='submit'>Update billboard</button></form>"
            "<p class='hint'>WiFi network: <b>S2-Billboard</b> &nbsp; Password: <b>billboard</b><br>Open <b>192.168.4.1</b> after connecting.</p>"
            "</body></html>");
  server.send(200, "text/html", page);
}

void handleSet()
{
  if (server.hasArg("text"))
  {
    message = server.arg("text");
    message.trim();
    if (message.length() == 0) message = " ";
  }
  if (server.hasArg("brightness")) brightness = constrain(server.arg("brightness").toInt(), 0, 15);
  if (server.hasArg("speed")) scrollSpeed = constrain(server.arg("speed").toInt(), 10, 250);
  if (server.hasArg("effect")) effectName = server.arg("effect");
  startAnimation();
  server.sendHeader("Location", "/");
  server.send(303, "text/plain", "Updated");
}

void setup()
{
  // Route ESP32-S2 SPI onto the requested FC-16 signal pins before MD_Parola starts.
  SPI.begin(SCK_PIN, -1, MOSI_PIN, CS_PIN);
  matrix.begin();
  startAnimation();

  WiFi.mode(WIFI_AP);
  WiFi.softAP(AP_SSID, AP_PASSWORD);
  server.on("/", HTTP_GET, handleRoot);
  server.on("/set", HTTP_GET, handleSet);
  server.begin();
}

void loop()
{
  server.handleClient();
  if (matrix.displayAnimate()) matrix.displayReset();
}

“Deploy to device” opens this project in Schematik, where you can flash it to your board over USB.

Project files

Shared by the author
stlbackBillboard.stl479 KBstlfrontBillboard.stl552 KB

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