Portable Bluetooth Hotkey Button, a ESP32 project

This project builds a portable Bluetooth hotkey button that sends a customizable keyboard shortcut (Ctrl+Alt+F9 by default) to any connected device. The single arcade button is housed in a compact enclosure and powered by a protected 18650 battery, making it ideal for triggering emergency functions, application shortcuts, or accessibility commands from anywhere within Bluetooth range.

The guide provides a complete wiring diagram, parts list, and step-by-step assembly instructions for integrating the ESP32 microcontroller, charging circuit, and power regulation. Customizable firmware handles debouncing, Bluetooth connectivity status indication via the button's LED, and reliable hotkey transmission with connection checking.

Wiring diagram

Gather all the parts

Qty	Component
1	Mini LED Arcade Button - 24mm Translucent Clear red, normally-open 24 mm translucent clear arcade button with integrated LED, requiring a 24 mm mounting hole. Normally-open momentary switch with separate LED contacts.
1	18650 Li-ion Cell 3.7 V, 2500 mAh protected 18650 lithium-ion cell, nominal 3.7 V, ~2500 mAh. Common for higher-capacity portable / battery-bank style projects; needs a holder and protection / charger circuit.
1	TP4056 Li-Ion/LiPo charger module with protection single-cell Li-ion with protection TP4056 single-cell Li-Ion/LiPo linear charger module, 5V USB input, 1A charge current (programmable). Common variants ship with DW01 protection. Pair with battery_lipo_storage for the cell.
1	3.3v Buck Boost 3.3 V regulated TI TPS63030/TPS63031 high-efficiency single-inductor buck-boost converter family with 1A switches. Used to hold a regulated rail when battery voltage crosses above and below the target output.

Assemble it in 4 steps

1. Prepare the enclosure and button

Make the mounting hole required by your chosen large red normally-open arcade button (24 mm for the selected catalog style). Fit the button and tighten its retaining nut; keep the switch terminals and LED terminals identifiable.

Choose a red button whose LED section is rated for 3.3 V or has an internal resistor.
Use an enclosure that cannot let the battery terminals or power-board solder joints touch metal.
Do not use a latching on/off switch as the hotkey button; it must be a momentary, normally-open switch.

2. Wire the button

Connect button SW1 to ESP32 GPIO27 and SW2 to an ESP32 GND pin. Connect LED+ to GPIO13 and LED- to ESP32 GND. The firmware uses GPIO27’s internal pull-up, so no extra switch resistor is needed.

Keep these wires short and strain-relieved.
GPIO13 turns the button light on only after the PC has connected over Bluetooth.
Do not connect the switch contact to 3.3 V; it is wired between GPIO27 and ground.

3. Build the protected battery and regulator chain

Install a protected 18650 cell in its holder. Connect battery +V to charger B+ and battery GND to charger B-. Connect charger OUT+ to regulator VIN and charger OUT- to regulator GND. Set the regulator output to exactly 3.3 V with a multimeter before connecting the ESP32.

Use the charger module’s protected OUT+/OUT- terminals for the load, not B+/B-.
A 2500 mAh cell is estimated at roughly 16 hours of active use; actual time depends heavily on Bluetooth connection activity and regulator efficiency.
Never short, puncture, reverse, or charge an 18650 cell without protection.
Do not connect the 4.2 V battery/charger output directly to the ESP32 3V3 pin.
Use only the TP4056 module’s 5 V USB input for charging.

4. Power the ESP32

Connect regulator VOUT to the ESP32 3V3 pin. Ensure regulator GND, charger OUT-, and the ESP32 GND pins are all common ground. Mount and insulate the boards so they cannot short against the enclosure or battery holder.

Verify 3.3 V again between ESP32 3V3 and GND before installing the ESP32.
Use a separate accessible USB opening for the TP4056 charging connector.
Do not feed the regulator’s 3.3 V output into ESP32 VIN/5V.
Disconnect battery power before changing wiring.

Review all connections

1. Connections between "button_1" and "ESP32"

Function	button_1	ESP32
`digital`	SW1	GPIO 27
`ground`	SW2	GND
`digital`	LED+	GPIO 13
`ground`	LED-	GND

2. Connections between "battery_1" and "ESP32"

Function	battery_1	ESP32
`power`	+V → TP4056 Li-Ion/LiPo charger module with protection B+	EXT
`ground`	GND → TP4056 Li-Ion/LiPo charger module with protection B-	EXT

3. Connections between "charger_1" and "ESP32"

Function	charger_1	ESP32
`power`	IN+ → 5 V USB charging supply	EXT
`ground`	IN- → USB charging supply ground	EXT
`power`	OUT+ → 3.3v Buck Boost VIN	EXT
`ground`	OUT- → 3.3v Buck Boost GND	EXT

4. Connections between "regulator_1" and "ESP32"

Function	regulator_1	ESP32
`power`	VOUT	3V3

Deploy the firmware

main.cppOpen in Schematik

#include <Arduino.h>
#include <BleKeyboard.h>


// Forward declarations
void sendHotkey();

constexpr uint8_t BUTTON_PIN = 27;
constexpr uint8_t BUTTON_LED_PIN = 13;
constexpr uint32_t DEBOUNCE_MS = 35;
constexpr uint32_t KEY_HOLD_MS = 40;

BleKeyboard bleKeyboard("Emergency Hotkey Button", "Schematik", 100);

bool rawLast = HIGH;
bool stableState = HIGH;
uint32_t rawChangedAt = 0;

void sendHotkey() {
  if (!bleKeyboard.isConnected()) {
    return;
  }

  bleKeyboard.press(KEY_LEFT_CTRL);
  bleKeyboard.press(KEY_LEFT_ALT);
  bleKeyboard.press(KEY_F9);
  delay(KEY_HOLD_MS);
  bleKeyboard.releaseAll();
}

void setup() {
  pinMode(BUTTON_PIN, INPUT_PULLUP);
  pinMode(BUTTON_LED_PIN, OUTPUT);
  digitalWrite(BUTTON_LED_PIN, LOW);
  bleKeyboard.begin();
}

void loop() {
  const bool connected = bleKeyboard.isConnected();
  digitalWrite(BUTTON_LED_PIN, connected ? HIGH : LOW);

  const bool rawNow = digitalRead(BUTTON_PIN);
  const uint32_t now = millis();

  if (rawNow != rawLast) {
    rawLast = rawNow;
    rawChangedAt = now;
  }

  if ((now - rawChangedAt) >= DEBOUNCE_MS && rawNow != stableState) {
    stableState = rawNow;
    if (stableState == LOW) {
      sendHotkey();
    }
  }

  delay(2);
}

Wiring diagram

Gather all the parts

Assemble it in 4 steps

1. Prepare the enclosure and button

2. Wire the button

3. Build the protected battery and regulator chain

4. Power the ESP32

Review all connections

1. Connections between "button_1" and "ESP32"

2. Connections between "battery_1" and "ESP32"

3. Connections between "charger_1" and "ESP32"

4. Connections between "regulator_1" and "ESP32"

Deploy the firmware

Make it yours in one click

Related projects

Create A Complete Electrical Schematic Esp32 Sma

ESP32 Kare Ekran Projeleri

Component Qty --------------------------- ------

ESP32 Stabilized Mini Drone