WiFi Button Status Monitor, a ESP32 project

This project turns an ESP32 into a WiFi-connected button status monitor. A push button wired to the microcontroller broadcasts its state over a local web interface, making it easy to check whether the button is pressed or released from any device on the network.

The guide includes a complete wiring diagram, parts list, and ready-to-flash firmware with debouncing logic to ensure reliable button detection. Assembly takes just a few minutes: connect the button to the ESP32, power it up, and open the status page in a web browser to see real-time button state updates.

Wiring diagram

Gather all the parts

Qty	Component
1	Push Button Momentary, normally open Momentary push button switch

Assemble it in 3 steps

1. Power off the ESP32

Disconnect the ESP32 DevKit v1 from USB before placing or wiring the button.

Use a normally-open momentary push button or the two switch terminals of a tactile button.
Do not connect GPIO21 to 3.3 V for this design; the firmware uses the ESP32's internal pull-up resistor.

2. Wire the button

Connect one button terminal to ESP32 GPIO21. Connect the opposite button terminal to an ESP32 GND pin. The button is active low: pressing it joins GPIO21 to ground.

For a 4-leg tactile switch, the two legs on each side are internally paired; use one leg from each opposite side.
No external resistor is required because INPUT_PULLUP is enabled in firmware.
Ensure the button connection is only between GPIO21 and GND.

3. Power and open the status page

Reconnect USB to power the ESP32. After deploying the firmware, connect a phone or computer to Wi-Fi network ESP32-Button using password pressrelease, then browse to http://192.168.4.1/.

The page refreshes once per second and displays either Button pressed or Button released.
This is a local ESP32 Wi-Fi network, not your home Wi-Fi.

Review all connections

1. Connections between "button_1" and "ESP32"

Function	button_1	ESP32
`digital`	SIGNAL	GPIO 21
`ground`	GND	GND

Deploy the firmware

main.cppOpen in Schematik

#include <Arduino.h>
#include <WiFi.h>
#include <WebServer.h>


// Forward declarations
void handleRoot();
void handleState();
void updateButton();

constexpr int BUTTON_PIN = 21;
const char *AP_SSID = "ESP32-Button";
const char *AP_PASSWORD = "pressrelease";

WebServer server(80);

bool stablePressed = false;
bool lastRawPressed = false;
unsigned long rawChangedAt = 0;
constexpr unsigned long DEBOUNCE_MS = 30;

const char PAGE[] PROGMEM = R"HTML(
<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <meta http-equiv="refresh" content="1">
  <title>ESP32 Button</title>
  <style>
    body { font-family: system-ui, sans-serif; max-width: 34rem; margin: 15vh auto; padding: 1rem; text-align: center; }
    .state { font-size: 2rem; font-weight: 700; padding: 1.2rem; border-radius: .6rem; }
    .pressed { color: #fff; background: #167a36; }
    .released { color: #2600e4ff; background: #303683ff; }
    small { display: block; margin-top: 1rem; color: #555; }
  </style>
</head>
<body>
  <h1>ESP32 Button</h1>
  <div id="state" class="state released">Loading…</div>
  <small>This page refreshes once per second.</small>
  <script>
    fetch('/state').then(r => r.json()).then(s => {
      const box = document.getElementById('state');
      box.textContent = s.pressed ? 'Button pressed' : 'Button released';
      box.className = 'state ' + (s.pressed ? 'pressed' : 'released');
    }).catch(() => {
      document.getElementById('state').textContent = 'Connection error';
    });
  </script>
</body>
</html>
)HTML";

void handleRoot() {
  server.send_P(200, "text/html", PAGE);
}

void handleState() {
  server.send(200, "application/json", stablePressed ? "{\"pressed\":true}" : "{\"pressed\":false}");
}

void updateButton() {
  const bool rawPressed = digitalRead(BUTTON_PIN) == LOW;
  const unsigned long now = millis();

  if (rawPressed != lastRawPressed) {
    lastRawPressed = rawPressed;
    rawChangedAt = now;
  }

  if (now - rawChangedAt >= DEBOUNCE_MS && stablePressed != rawPressed) {
    stablePressed = rawPressed;
  }
}

void setup() {
  pinMode(BUTTON_PIN, INPUT_PULLUP);
  stablePressed = digitalRead(BUTTON_PIN) == LOW;
  lastRawPressed = stablePressed;
  rawChangedAt = millis();

  WiFi.mode(WIFI_AP);
  WiFi.softAP(AP_SSID, AP_PASSWORD);

  server.on("/", HTTP_GET, handleRoot);
  server.on("/state", HTTP_GET, handleState);
  server.begin();
}

void loop() {
  updateButton();
  server.handleClient();
}