Tools, APP Software Used etc.

	KiCad 9.0
	PlatformIO PlatformIO Labs
	Autodesk Fusion 360 Autodesk

Description

ESP32-C3 BLE Keyboard - Battery Powered with USB-C Charging

## Project Motivation

While working, I often needed a simple Bluetooth keyboard with customizable shortcut keys.

Instead of buying an expensive commercial product, I decided to create my own compact

2-key BLE keyboard using ESP32-C3.

## Key Features

This project successfully achieves the following:

✅ **2-Key Bluetooth HID Keyboard** - Works as a standard Bluetooth keyboard with any PC/Mac

✅ **Battery Powered** - Fully portable with integrated Li-ion battery support

✅ **USB Type-C Charging** - Convenient charging with built-in charging circuit

✅ **Safe Operation** - Protection IC prevents overcurrent and overvoltage

✅ **Auto Programming** - No need to press BOOT/EN buttons during firmware upload

✅ **Compact Design** - Small PCB footprint, easy to carry

## Technical Details

### Power Management

- **Charging IC**: TP4056 with protection IC

- **Battery**: Single-cell Li-ion battery (3.7V)

- **Voltage Regulation**: Stable 3.3V output for ESP32-C3

- **USB Type-C**: Charging and power supply with proper CC pin configuration

### Programming Interface

- **USB-UART Bridge**: FT231XS (or CH340/CP2102) for serial communication

- **Auto-Reset Circuit**: DTR/RTS controlled BOOT/EN pins for automatic programming

- **Manual Override**: Physical BOOT and EN buttons included for troubleshooting

### Bluetooth Operation

- **BLE HID Profile**: Standard Bluetooth Low Energy keyboard implementation

- **Key Assignment**: 2 programmable keys (fully customizable via firmware)

- **Low Power**: BLE enables extended battery life

- **Wide Compatibility**: Works with Windows, macOS, Linux, Android, iOS

## How It Works

1. **Connect via Bluetooth**: Pair with any device supporting BLE keyboards

2. **Assign Keys**: Program your preferred shortcuts (Enter, Space, Ctrl+C, etc.)

3. **Use Wirelessly**: Press keys to send commands to your computer

4. **Recharge Easily**: Plug in USB-C cable when battery runs low

## Use Cases

- Quick access to frequently used shortcuts during work

- Custom macro pad for video editing, CAD, or programming

- Minimalist desk setup with wireless control

- Educational project for learning ESP32 BLE programming

Code

2-Key BLE Keyboard Firmware for ESP32-C3

C/C++

#include <Arduino.h>

/*
 * ESP32-C3 2キーBluetoothキーボード（セキュリティ設定修正版）
 * GPIO1: ENTERキー
 * GPIO3: スペースキー
 * 
 * 必要なライブラリ:
 * - ESP32-BLE-Keyboard by T-vK
 *   Arduino IDEのライブラリマネージャーからインストール可能
 * 
 * 配線:
 * - タクトスイッチ1の片側: GPIO1
 * - タクトスイッチ1のもう片側: GND
 * - タクトスイッチ2の片側: GPIO3
 * - タクトスイッチ2のもう片側: GND
 * - ESP32-C3の3V3とGNDに電源を供給
 */

#include <BleKeyboard.h>
#include <NimBLEDevice.h>

// ピン設定
const int BUTTON_ENTER_PIN = 1;  // ENTERキー用タクトスイッチ
const int BUTTON_SPACE_PIN = 3;  // スペースキー用タクトスイッチ

// チャタリング防止用の設定
const unsigned long DEBOUNCE_DELAY = 50;  // 50ミリ秒

// ENTER用のチャタリング管理
unsigned long lastDebounceTimeEnter = 0;
int lastButtonStateEnter = HIGH;
int buttonStateEnter = HIGH;

// スペース用のチャタリング管理
unsigned long lastDebounceTimeSpace = 0;
int lastButtonStateSpace = HIGH;
int buttonStateSpace = HIGH;

// BLEキーボードの初期化
BleKeyboard bleKeyboard("ESP32 Keyboard", "Espressif", 100);

void setup() {
  // シリアル通信の初期化（デバッグ用）
  Serial.begin(115200);
  delay(1000);
  Serial.println("ESP32-C3 2-Key BLE Keyboard Starting...");
  
  // ボタンピンの設定（内部プルアップ抵抗を有効化）
  pinMode(BUTTON_ENTER_PIN, INPUT_PULLUP);
  pinMode(BUTTON_SPACE_PIN, INPUT_PULLUP);
  
  // BLEセキュリティ設定を変更（ペアリング簡易化）
  Serial.println("Configuring BLE Security (No PIN required)...");
  
  // NimBLEのセキュリティ設定を変更
  NimBLEDevice::setSecurityAuth(false, false, true);  // bonding=false, mitm=false, sc=true
  NimBLEDevice::setSecurityIOCap(BLE_HS_IO_NO_INPUT_OUTPUT);  // PIN入力なし
  
  // BLEキーボードの開始
  Serial.println("Initializing BLE Keyboard...");
  bleKeyboard.begin();
  
  Serial.println("Ready! Waiting for Bluetooth connection...");
  Serial.println("Please pair from your device's Bluetooth settings.");
  Serial.println("No PIN required!");
}

void loop() {
  // BLE接続状態の確認
  if(bleKeyboard.isConnected()) {
    
    // ========== ENTERキーの処理 ==========
    int readingEnter = digitalRead(BUTTON_ENTER_PIN);
    
    if (readingEnter != lastButtonStateEnter) {
      lastDebounceTimeEnter = millis();
    }
    
    if ((millis() - lastDebounceTimeEnter) > DEBOUNCE_DELAY) {
      if (readingEnter != buttonStateEnter) {
        buttonStateEnter = readingEnter;
        
        if (buttonStateEnter == LOW) {
          Serial.println("ENTER key pressed!");
          bleKeyboard.write(KEY_RETURN);
          delay(100);
        }
      }
    }
    
    lastButtonStateEnter = readingEnter;
    
    // ========== スペースキーの処理 ==========
    int readingSpace = digitalRead(BUTTON_SPACE_PIN);
    
    if (readingSpace != lastButtonStateSpace) {
      lastDebounceTimeSpace = millis();
    }
    
    if ((millis() - lastDebounceTimeSpace) > DEBOUNCE_DELAY) {
      if (readingSpace != buttonStateSpace) {
        buttonStateSpace = readingSpace;
        
        if (buttonStateSpace == LOW) {
          Serial.println("SPACE key pressed!");
          bleKeyboard.write(' ');  // スペースキー
          delay(100);
        }
      }
    }
    
    lastButtonStateSpace = readingSpace;
    
  } else {
    // 接続待ち状態
    static unsigned long lastPrintTime = 0;
    if (millis() - lastPrintTime > 5000) {
      Serial.println("Waiting for Bluetooth connection...");
      lastPrintTime = millis();
    }
  }
  
  // CPU負荷を下げるための短い待機時間
  delay(10);
}

Schematic and Layout

2-Key BLE Keyboard for ESP32-C3

Schematic.pdf

CAD-Custom parts and enclosures

3D Printable Enclosure for ESP32-C3 2-Key Keyboard

3D.step

Download Gerbers Download BOM(Bill of materials)

Dec 28,2025

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ESP32-C3 BLE Keyboard - Battery Powered with USB-C Charging

Compact ESP32-C3 with 2-key BLE keyboard, USB-C charging, and Li-ion battery. Ideal for custom macro pads and portable devices.

Published: Dec 28,2025

Standard PCB

Download Gerber file 0

BOM(Bill of materials)

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