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2 layers94 × 67 mmSpectre, the printed circuit board in 3D

Spectre

guardianep/espectrum

A USB audio mixer PCB with per-app volume control. Link any three applications to physical sliders and control their volume on the fly without tabbing out.

Open in PCBKitView on GitHub.kicad_pcb
Size
94 × 67 mm
Copper layers
2
Thickness
1.6 mm
Parts
39
Nets
52
Pads
183
Tracks, vias
486, 27
Routed
Yes
KiCad
KiCad 10.0 (file 20260206)
Created
5 Oct 2026
Updated
11 Oct 2026

Overview

Spectre is an open-source printed circuit board by guardianep, from the guardianep/espectrum repository on GitHub. It is a 2-layer board of 94 × 67 mm with 39 parts on 52 nets, routed with 486 tracks and 27 vias.

It is built around the ESP32-C3-DEVKITM-1 and SK6812MINI-E. Its parts include 30 diodes, 3 resistors, 2 ICs and 1 capacitor. It belongs with the ESP32 and RISC-V boards of this library.

Main components

2

README

README.md

Spectre Audio Mixer

A USB audio mixer PCB with per-app volume control. Link any three applications to physical sliders and control their volume on the fly without tabbing out.

Features

  • Link any three apps to individual volume sliders
  • Seamless app-to-slider mapping via desktop controller
  • LED level indicators (1-10) showing current volume per slider
  • OLED display showing active app mappings
  • Reactive LED indicators synced to system volume
  • Works in games without alt-tabbing

Hardware Design

KiCad files available in hardware/kicad/:

  • Schematic: Spectre.kicad_sch
  • PCB Layout: Spectre.kicad_pcb

Spectre PCB final rendering

Microcontroller:

  • ESP32-C3-DevKitM-1

Sensors & Controls:

  • 3x Potentiometer sliders (10kΩ)
  • GPIO pins 3, 4, 5 for analog input

Output:

  • 30x SK6812MINI-E addressable RGB LEDs (10 per slider)
  • SSD1306 OLED display (128x64) via I2C
  • 5V and 3.3V power rails with 220µF decoupling capacitor
  • 360Ω series resistors on LED data lines

Power:

  • USB-C (5V from ESP32)
  • Separate 5V rail for LEDs, 3.3V for logic

Software

Desktop Controller (Python):

  • Tkinter GUI for app selection
  • Serial communication at 115200 baud
  • Sends config format: S1:Chrome|S2:Spotify|S3:Discord

Firmware (ESP32-C3):

  • Arduino framework with PlatformIO
  • Adafruit NeoPixel library for LED control
  • Adafruit SSD1306 library for OLED display
  • Serial parsing for configuration updates

Setup

Hardware Assembly

  1. Solder SK6812MINI-E LEDs to GPIO 0, 1, 2 (10 each)
  2. Connect potentiometers to GPIO 3, 4, 5
  3. Wire SSD1306 OLED via I2C (SDA, SCL)
  4. Add 220µF capacitor across 5V/GND rails
  5. Add 360Ω resistors on LED data lines

Firmware

  1. Install PlatformIO
  2. Build and upload to ESP32-C3
  3. Connect via USB (COM3 on Windows)

Desktop App

bash
pip install pyserial psutil
python spectre_controller.py

Usage

  1. Run desktop controller
  2. Select apps from dropdown menus (Slider 1, 2, 3)
  3. Click "Save Configuration"
  4. OLED displays active app mappings
  5. Move sliders to control individual app volumes
  6. LED bars show volume level (1-10 LEDs lit)

Status

  • Firmware: Complete (Steps 1-4 done)
  • Desktop Controller: BETA (app selection refinement in progress)
  • Hardware: PCB designed, awaiting fabrication

Parts

39
QtyValueFootprintReferences
30SK6812MINI-Enew fixed models:SK6812MINI-E_fixed_fixedD1, D2, D10, D11, D12, D13, D14, D15, D16, D17, D18, D19, D20, D21, D22, D23 +14
3330Resistor_THT:R_Axial_DIN0207_L6.3mm_D2.5mm_P2.54mm_VerticalR1, R2, R3
3R_Potentiometernew fixed models:Potentiometer_Bourns_PTA3043_Single_SlideRV1, RV2, RV3
1100Capacitor_THT:CP_Radial_D5.0mm_P2.00mmC1
1ER_OLEDM0.91_1x-I2Cnew fixed models:ER_OLEDM0.91_1x-I2C-new-newserU2
1ESP32-C3-DevKitM-1new fixed models:ESP32-C3-DevKitM-1-3U1

Questions

How big is the Spectre PCB?

It measures 94 × 67 mm and has 2 copper layers, 1.6 mm thick.

What parts does the Spectre use?

39 parts, built around the ESP32-C3-DEVKITM-1 and SK6812MINI-E. The full list of its parts is on this page, with links to each part's symbol and footprint where PCBKit's library has them.

Where can I download the Spectre KiCad files?

From the guardianep/espectrum repository on GitHub, at the commit this page was made from: the board is Hardware/kicad/Spectre.kicad_pcb and its schematic Hardware/kicad/Spectre.kicad_sch. PCBKit opens the board in the browser, with nothing to install.

Can I use the Spectre design in my own project?

Its repository states no licence, so its author keeps all rights: ask guardianep before reusing the design.

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