CH32X035 USB HID Keyboard Library

A high-performance, efficient USB HID Keyboard library tailored for the WCH CH32X035 RISC-V microcontroller series.

This library leverages the hardware USBFS peripheral and synchronized interrupts to provide a robust, ultra-fast keyboard emulation interface. It allows your CH32X035 to type into any computer (Windows, macOS, Linux, Android) just like a standard physical keyboard, with no drivers required.

Features

• Class Compliant: Works natively as a standard USB Keyboard on all major operating systems.
• Hardware Synchronization: Uses interrupt flags to synchronize data transfer with the USB host, preventing data loss during high-speed typing.
• High Performance: Capable of sending keystrokes at maximum USB polling speed (up to 500 chars/sec in raw mode).
• Compatibility Mode: Includes an adjustable delay mechanism (setDelay) to ensure reliability with slower GUI aplicaciones.
• Full Modifier Support: Easy access to Ctrl, Shift, Alt, and GUI (Windows/Command) keys.

API Overview

The library adheres to the standard Arduino Keyboard API conventions while adding specific enhancements for the CH32X035 architecture.

Function	Description
Keyboard.begin()	Initializes the USB stack and enumerates the device.
Keyboard.print("text")	Types a string of characters.
Keyboard.println("text")	Types a string followed by a newline (Enter).
Keyboard.write(key)	Presses and immediately releases a single key.
Keyboard.press(key)	Holds a key down (useful for combos like Ctrl+C).
Keyboard.release(key)	Releases a specific key.
Keyboard.releaseAll()	Releases all currently held keys.
Keyboard.setDelay(ms)	New: Adds a safety delay (in ms) between keystrokes to prevent errors in slow apps.

Supported Special Keys

The library defines standard constants for non-printing keys:

Key Constant	Description	Key Constant	Description
KEY_LEFT_CTRL	Left Control	KEY_RETURN	Enter
KEY_LEFT_SHIFT	Left Shift	KEY_ESC	Escape
KEY_LEFT_ALT	Left Alt	KEY_BACKSPACE	Backspace
KEY_LEFT_GUI	Windows / Command	KEY_TAB	Tab
KEY_UP_ARROW	Up Arrow	KEY_CAPS_LOCK	Caps Lock
KEY_DOWN_ARROW	Down Arrow	KEY_F1 - KEY_F12	Function Keys

Installation

1. Download this repository as a ZIP file.
2. Open the Arduino IDE.
3. Go to Sketch -> Include Library -> Add .ZIP Library...
4. Select the downloaded ZIP file.
5. Restart the IDE.

Usage Guide

1. Basic Setup

Include the library and initialize it in setup().

#include <USBHIDKeyboard.h>

void setup() {
    // Initialize USB Keyboard stack
    Keyboard.begin();
    
    // Recommended: Give the host OS time to enumerate
    delay(2000);
}

void loop() {
    // Your logic here
}

2. Typing Text & Compatibility

If you are typing into a fast application, you can use the default speed. For apps like Notepad on Windows, it's safer to add a small delay.

void setup() {
    Keyboard.begin();
    // Add a 10ms delay between keystrokes for compatibility
    Keyboard.setDelay(10); 
    delay(2000);
}

void loop() {
    Keyboard.println("Hello from CH32X035!");
    delay(5000);
}

3. Key Combinations (Shortcuts)

Use press() and releaseAll() for complex shortcuts.

void openTaskManager() {
    Keyboard.press(KEY_LEFT_CTRL);
    Keyboard.press(KEY_LEFT_SHIFT);
    Keyboard.press(KEY_ESC);
    delay(50);
    Keyboard.releaseAll();
}

void copy() {
    Keyboard.press(KEY_LEFT_CTRL);
    Keyboard.press('c');
    delay(50);
    Keyboard.releaseAll();
}

Credits & Acknowledgements

This library was developed by NoNamedCat.

It is architecturally inspired by and built upon the CH32X035_USBSerial library.

Special thanks to jobitjoseph for his excellent work on the CH32X035 USB CDC implementation, which provided the essential foundation for the low-level USBFS initialization and endpoint management used in this project.

License

This project is licensed under the MIT License - see the LICENSE file for details.