REGOLO

REGOLO is a 10-channel USB control surface designed for software-based audio volume control.

Its purpose is to provide direct physical control over system and application audio, such as:

• master system output
• main microphone
• secondary microphone
• browser audio
• music playback
• voice chat
• DAW / creative software
• virtual buses or per-application outputs

REGOLO is not intended to be an analog audio mixer. It is a hardware controller for software-side audio mixing.

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Project goal

REGOLO is designed to make everyday audio routing faster and more intuitive by providing dedicated physical controls for tasks like:

• raising or lowering an application's volume without switching windows
• muting a specific channel instantly
• getting clear visual feedback about channel state
• assigning each channel to a different audio source or destination

A typical use case is a desktop, streaming, or studio setup where multiple audio sources coexist: system output, microphones, browser audio, media players, communication apps, and creative tools.

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How it works

The intended architecture is simple:

1. The hardware exposes 10 independent physical channels.
2. Each channel provides the microcontroller with:
   • an analog potentiometer position
   • a digital mute switch state
   • a status LED control line
3. The firmware reads the inputs and sends events to the computer over USB.
4. Host software maps those events to system or per-application volume and mute controls.

This means the actual audio logic lives on the host computer, while REGOLO acts as a dedicated physical interface.

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Main features

• 10 independent channels
• Continuous physical control for each channel via potentiometer
• Dedicated mute per channel
• Status LED for visual feedback
• USB-C connectivity
• CH32V203 microcontroller with integrated full-speed USB
• Hardware designed in KiCad
• Planned firmware development with WCH Fun

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Current hardware architecture

Based on the current repository state, the hardware is organized as follows.

Channels

Each channel is replicated as the same building block and exposes:

• A_OUT: analog output from the volume control
• mute: mute switch state
• status: LED control line

In the PCB project, each channel includes:

• one potentiometer (RS301111A01G local footprint)
• one DPDT switch (XKB5858-Z-TP)
• one status LED with supporting passive components

MCU

The device is built around a WCH CH32V203, used to:

• sample the 10 analog signals (ADC_[1..10])
• read the 10 switches (SW_[1..10])
• drive the 10 LEDs (LED_[1..10])
• communicate with the host over USB

The schematic also includes programming and debug-related signals such as:

• SWDIO
• SWCLK
• RST
• BOOT0
• BOOT1

USB and power

The current USB section includes:

• USB-C USB 2.0 connector
• USBLC6-2P6 ESD protection on the data lines
• polyfuse on USB power input
• AZ1117CH2-3.3 regulator for the 3.3V rail

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Current status

The repository currently focuses on the hardware design of the device.

Present

• PCB project in pcb/mobo/
• modular schematics for:
  • channel
  • MCU
  • USB
• local KiCad symbols and footprints in pcb/components/

Not yet included

• device firmware (firmware/ is currently empty)
• host-side software to map hardware controls to actual system/application volumes

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Project structure

regolo/
├── firmware/          # Device firmware (to be developed)
├── pcb/
│   ├── components/    # Local KiCad symbols and footprints
│   └── mobo/          # Main board project
│       ├── mobo.kicad_pro
│       ├── mobo.kicad_sch
│       ├── mobo.kicad_pcb
│       ├── channel.kicad_sch
│       ├── mcu.kicad_sch
│       └── usb.kicad_sch
├── LICENSE
└── README.md

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Opening the hardware project

To inspect or modify the PCB design:

1. install KiCad 10 or a compatible version
2. open:

pcb/mobo/mobo.kicad_pro

The project uses local libraries stored in:

pcb/components/

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Firmware

The firmware is planned around WCH Fun.

WCH Fun is a lightweight framework well suited for WCH microcontrollers and fits the goals of the project:

• direct low-level control
• small and simple firmware architecture
• straightforward USB and peripheral handling
• good fit for a dedicated embedded control device

The firmware side is expected to handle:

• sampling the 10 potentiometers
• reading the 10 mute switches
• updating the LEDs
• exposing the controller state to the host over USB

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Expected use cases

Example 10-channel assignments:

1. system master output
2. main microphone
3. secondary microphone
4. browser
5. music
6. Discord / voice chat
7. game audio
8. DAW
9. monitoring / recording bus
10. virtual output / streaming bus

The channel mapping is expected to be software-configurable.

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Important note

As the current design suggests, REGOLO is a control surface, not a board that directly processes analog audio signals. Volume control is performed in software, with the operating system or a host application responsible for managing the actual audio levels.

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License

REGOLO uses a split licensing model that matches the different nature of its hardware and software sources.

Hardware design

The hardware design files are licensed under the CERN Open Hardware Licence Version 2 - Strongly Reciprocal (CERN-OHL-S-2.0).

This applies to the open hardware sources in the repository, including for example:

• schematics
• PCB layout files
• KiCad symbols
• KiCad footprints

The full hardware license text is available in LICENSE.

Firmware

The firmware in firmware/ is licensed under the MIT License.

The firmware license text is available in firmware/LICENSE.

This gives the embedded software side a simple and widely used open source license, while keeping the hardware design under a proper open hardware license.

Unless otherwise noted:

• hardware design files are provided under CERN-OHL-S-2.0
• firmware source code is provided under MIT

If host-side software is added to the repository in the future, it may follow the same MIT license or be licensed separately where appropriate.