ESP32C3 BLE Keyboard library

This library allows you to make the ESP32C3 act as a Bluetooth Keyboard and control what it does.
You might also be interested in:

• ESP32-BLE-Mouse
• ESP32-BLE-Gamepad

Features

• Send key strokes
• Send text
• Press/release individual keys
• Media keys are supported
• Read Numlock/Capslock/Scrolllock state
• Set battery level (basically works, but doesn't show up in Android's status bar)
• Compatible with Android
• Compatible with Windows
• Compatible with Linux
• Compatible with MacOS X (not stable, some people have issues, doesn't work with old devices)
• Compatible with iOS (not stable, some people have issues, doesn't work with old devices)
• For Seeed Studio XIAO ESP32C3
• セキュリティの関係でNimBLE-ArduinoがヘッダーでOnになっています

Installation

• (Make sure you can use the ESP32 with the Arduino IDE. Instructions can be found here.)
• Download the latest release of this library from this page.
• In the Arduino IDE go to "Sketch" -> "Include Library" -> "Add .ZIP Library..." and select the file you just downloaded.
• You can now go to "File" -> "Examples" -> "ESP32C3 BLE Keyboard" and select any of the examples to get started.

Example

/**
 * This example turns the ESP32 into a Bluetooth LE keyboard that presses a media key
 * https://github.com/T-vK/ESP32-BLE-Keyboardを改変しESP32C3でのメディアコントロールに特化したやつ
 * NimBLE-Arduinoをライブラリマネージャからダウンロードしてください
 */
#include <BleKeyboard.h>

BleKeyboard bleKeyboard("ESP32 Media Keybord","Mendako Lab",50);

void setup() {
  Serial.begin(115200);
  Serial.println("Starting BLE work!");
  bleKeyboard.begin();
  
  // 使えるメディア制御コマンド
  // keyIDの実装参考
  // https://www.usb.org/document-library/hid-usage-tables-14
  /*
  KEY_MEDIA_NEXT_TRACK
  KEY_MEDIA_PREVIOUS_TRACK
  KEY_MEDIA_STOP 
  KEY_MEDIA_PLAY
  KEY_MEDIA_PAUSE
  KEY_MEDIA_MUTE
  KEY_MEDIA_VOLUME_UP
  KEY_MEDIA_VOLUME_DOWN
  */
  
  // 入力ピンの設定
  // D6,8,9はめんどくさいので使わない
  // 詳細は → https://lab.seeed.co.jp/entry/2023/04/03/120000
  pinMode(D0,INPUT_PULLUP);    //GPIO0(BOOT)をプルアップ付き入力設定
  pinMode(D1,INPUT_PULLUP);    //GPIO0(BOOT)をプルアップ付き入力設定
  pinMode(D2,INPUT_PULLUP);    //GPIO0(BOOT)をプルアップ付き入力設定
  pinMode(D3,INPUT_PULLUP);    //GPIO0(BOOT)をプルアップ付き入力設定
  pinMode(D4,INPUT_PULLUP);    //GPIO0(BOOT)をプルアップ付き入力設定
  pinMode(D5,INPUT_PULLUP);    //GPIO0(BOOT)をプルアップ付き入力設定
  pinMode(D7,INPUT_PULLUP);    //GPIO0(BOOT)をプルアップ付き入力設定
  pinMode(D10,INPUT_PULLUP);    //GPIO0(BOOT)をプルアップ付き入力設定

}

void loop() {
  // 長押し判定用のフラグ
  static bool flag_KEY_MEDIA_NEXT_TRACK = false;
  static bool flag_KEY_MEDIA_PREVIOUS_TRACK = false;
  if(bleKeyboard.isConnected()) {
    if(digitalRead(D0) == LOW && flag_KEY_MEDIA_NEXT_TRACK == false){
      Serial.println("Sending Scan Next Track media key...");
      flag_KEY_MEDIA_NEXT_TRACK = true;
      bleKeyboard.press(KEY_MEDIA_NEXT_TRACK);
    }
    else if(digitalRead(D0) == HIGH && flag_KEY_MEDIA_NEXT_TRACK == true){
      flag_KEY_MEDIA_NEXT_TRACK = false;
      bleKeyboard.release(KEY_MEDIA_NEXT_TRACK);
    }
    if(digitalRead(D1) == LOW && flag_KEY_MEDIA_PREVIOUS_TRACK == false){
      Serial.println("Sending Scan Previous Track media key...");
      flag_KEY_MEDIA_PREVIOUS_TRACK = true;
      bleKeyboard.press(KEY_MEDIA_PREVIOUS_TRACK);
    }
    else if(digitalRead(D1) == HIGH && flag_KEY_MEDIA_PREVIOUS_TRACK == true){
      flag_KEY_MEDIA_PREVIOUS_TRACK = false;
      bleKeyboard.release(KEY_MEDIA_PREVIOUS_TRACK);
    }
    if(digitalRead(D2) == LOW){
      Serial.println("Sending Stop media key...");
      bleKeyboard.write(KEY_MEDIA_STOP);
      delay(200);
    }
    if(digitalRead(D3) == LOW){
      Serial.println("Sending Play media key...");
      bleKeyboard.write(KEY_MEDIA_PLAY);
      delay(200);
    }
    if(digitalRead(D4) == LOW){
      Serial.println("Sending Pause media key...");
      bleKeyboard.write(KEY_MEDIA_PAUSE);
      delay(200);
    }
    if(digitalRead(D5) == LOW){
      Serial.println("Sending Mute media key...");
      bleKeyboard.write(KEY_MEDIA_MUTE);
      delay(200);
    }
    if(digitalRead(D7) == LOW){
      Serial.println("Sending Volume Increment media key...");
      bleKeyboard.write(KEY_MEDIA_VOLUME_UP);
      delay(50);
    }
    if(digitalRead(D10) == LOW){
      Serial.println("Sending Volume Decrement media key...");
      bleKeyboard.write(KEY_MEDIA_VOLUME_DOWN);
      delay(50);
    }
  }
}

API docs

The BleKeyboard interface is almost identical to the Keyboard Interface, so you can use documentation right here: https://www.arduino.cc/reference/en/language/functions/usb/keyboard/

Just remember that you have to use bleKeyboard instead of just Keyboard and you need these two lines at the top of your script:

#include <BleKeyboard.h>
BleKeyboard bleKeyboard;

In addition to that you can send media keys (which is not possible with the USB keyboard library). Supported are the following:

• KEY_MEDIA_NEXT_TRACK
• KEY_MEDIA_PREVIOUS_TRACK
• KEY_MEDIA_STOP
• KEY_MEDIA_PLAY_PAUSE
• KEY_MEDIA_MUTE
• KEY_MEDIA_VOLUME_UP
• KEY_MEDIA_VOLUME_DOWN
• KEY_MEDIA_WWW_HOME
• KEY_MEDIA_LOCAL_MACHINE_BROWSER // Opens "My Computer" on Windows
• KEY_MEDIA_CALCULATOR
• KEY_MEDIA_WWW_BOOKMARKS
• KEY_MEDIA_WWW_SEARCH
• KEY_MEDIA_WWW_STOP
• KEY_MEDIA_WWW_BACK
• KEY_MEDIA_CONSUMER_CONTROL_CONFIGURATION // Media Selection
• KEY_MEDIA_EMAIL_READER

There is also Bluetooth specific information that you can set (optional): Instead of BleKeyboard bleKeyboard; you can do BleKeyboard bleKeyboard("Bluetooth Device Name", "Bluetooth Device Manufacturer", 100);. (Max lenght is 15 characters, anything beyond that will be truncated.)
The third parameter is the initial battery level of your device. To adjust the battery level later on you can simply call e.g. bleKeyboard.setBatteryLevel(50) (set battery level to 50%).
By default the battery level will be set to 100%, the device name will be ESP32 Bluetooth Keyboard and the manufacturer will be Espressif.
There is also a setDelay method to set a delay between each key event. E.g. bleKeyboard.setDelay(10) (10 milliseconds). The default is 8.
This feature is meant to compensate for some applications and devices that can't handle fast input and will skip letters if too many keys are sent in a small time frame.

NimBLE-Mode

The NimBLE mode enables a significant saving of RAM and FLASH memory.

Comparison (SendKeyStrokes.ino at compile-time)

Standard

RAM:   [=         ]   9.3% (used 30548 bytes from 327680 bytes)
Flash: [========  ]  75.8% (used 994120 bytes from 1310720 bytes)

NimBLE mode

RAM:   [=         ]   8.3% (used 27180 bytes from 327680 bytes)
Flash: [====      ]  44.2% (used 579158 bytes from 1310720 bytes)

Comparison (SendKeyStrokes.ino at run-time)

	Standard	NimBLE mode	difference
ESP.getHeapSize()	296.804	321.252	+ 24.448
ESP.getFreeHeap()	143.572	260.764	+ 117.192
ESP.getSketchSize()	994.224	579.264	- 414.960

How to activate NimBLE mode?

ArduinoIDE:

Uncomment the first line in BleKeyboard.h

#define USE_NIMBLE

PlatformIO:

Change your platformio.ini to the following settings

lib_deps = 
  NimBLE-Arduino

build_flags = 
  -D USE_NIMBLE

Credits

Credits to chegewara and the authors of the USB keyboard library as this project is heavily based on their work!
Also, credits to duke2421 who helped a lot with testing, debugging and fixing the device descriptor! And credits to sivar2311 for adding NimBLE support, greatly reducing the memory footprint, fixing advertising issues and for adding the setDelay method.