CH32X035 USB MIDI Library

A comprehensive and efficient USB MIDI device library tailored for the WCH CH32X035 RISC-V microcontroller series.

This library leverages the hardware USBFS peripheral to provide a low-latency, class-compliant MIDI interface. No drivers are needed on host operating systems (Windows, macOS, Linux, Android, iOS).

Features

• Class Compliant: Works natively without drivers on all major operating systems.
• Bi-directional Communication: Send and receive MIDI messages seamlessly.
• Event-Driven Architecture: Register efficient C++ callbacks to handle specific incoming messages (Note On/Off, Control Change, etc.), avoiding complex parsing in your main loop.
• Full Standard Support: Supports the entire range of standard channel voice messages and real-time system messages.
• Hardware Optimized: Built on top of the CH32X035 USBFS for minimal overhead.

Supported MIDI Messages

This library supports sending and receiving the following MIDI specifications:

Message Type	Send	Receive (Callback)	Description
Note On	✅	✅	Trigger a note
Note Off	✅	✅	Stop a note
Control Change (CC)	✅	✅	Knobs, faders, pedals
Program Change (PC)	✅	✅	Change instrument/preset
Pitch Bend	✅	✅	14-bit pitch modification
Aftertouch (Channel)	✅	✅	Global pressure
Poly Pressure	✅	✅	Per-key pressure
Real-Time Messages	✅	✅	Clock, Start, Stop, Continue

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(). Crucial: You must call USBMIDI.poll() inside your loop() to process USB events.

#include <USBMIDI.h>

void setup() {
    // Initialize USB MIDI stack
    USBMIDI.begin();
}

void loop() {
    // Must be called frequently to handle USB traffic
    USBMIDI.poll();
}

2. Sending MIDI Data

It is recommended to avoid delay() so that USBMIDI.poll() runs continuously. Here is a non-blocking example using millis():

unsigned long lastTime = 0;
bool noteOn = false;

void loop() {
    // 1. ALWAYS poll USB first
    USBMIDI.poll();

    // 2. Non-blocking timer logic
    unsigned long now = millis();
    if (now - lastTime >= 500) {
        lastTime = now;

        if (!noteOn) {
            USBMIDI.sendNoteOn(0, 60, 127); // Note On
            noteOn = true;
        } else {
            USBMIDI.sendNoteOff(0, 60, 0);  // Note Off
            noteOn = false;
        }
    }
}

3. Receiving MIDI Data (Callbacks)

Instead of checking buffers manually, define functions that will be called automatically when a message arrives.

// Define callback functions
void handleNoteOn(uint8_t channel, uint8_t note, uint8_t velocity) {
    // Toggle an LED or play a sound
}

void handleControlChange(uint8_t channel, uint8_t controller, uint8_t value) {
    // Update internal parameters
}

void handleSystemRealTime(uint8_t realtimebyte) {
    if (realtimebyte == 0xF8) {
        // MIDI Clock tick
    }
}

void setup() {
    USBMIDI.begin();

    // Register callbacks
    USBMIDI.setHandleNoteOn(handleNoteOn);
    USBMIDI.setHandleControlChange(handleControlChange);
    USBMIDI.setHandleRealTime(handleSystemRealTime);
}

void loop() {
    USBMIDI.poll();
}

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.