Open Pedalboard Mainboard

Mainboard for processing audio and/or MIDI data on a pedalboard.

Open Source Hardware	OSHWA Certification

This PCB is designed with KiCad 8

Design Goals

• Visual Feedback with RGB LED Rings
• Modular Design:
  • The device can be used:
    1. MIDI controller only (Low Cost)
    2. both for MIDI and Audio, communication between the modules is done via MIDI.
  • MIDI Module has independent microcontroller and firmware with immediate startup
  • Optional Power supply module if no USB Power is available on the board.
• Maker friendly
  • Use of existing modules for the heavy lifting
  • Use of common components
• Flat design: target for case height: 30mm

Modules

Audio Processing

• Raspberry Pi Compute Module 4
  • Flexible memory options for cost optimisation
  • (optional) WiFi
  • Very low latency (around 2ms when using ELK Audio OS)
• Pedalboard Soundcard DAC ADC (under construction)
  • Two channel Differential input/output
• or HiFiBerry DAC+ ADC PRO
  • Hiqh Quality Stereo Input/Output
• USB A Host
• Mini USB Device mode (for firmware update)

MIDI and Control Surface

• 200mm x 100mm control surface. Still not too large but can hold 6 buttons.
• Raspberry RP-2040 processor with a custom firmware that can be updated via USB or also from the audio module via WLAN.
• 6 Buttons supporting to trigger on push, on release, long and short presses
• 2 Rotary Encoders with additional push button
• 2 Inputs for Expression Pedal
• 2 RGB Leds
• 8 RGB LED-rings around each foot button.
• (Optional) RGB Matrix: in a Matrix of RGB Pins even more information can be expressed and readable from a large distance. For example the current preset number or a db meter value.
• STEMMA I2C connector for 2 OLED displays
• I2C EEPROM for config storage
• Flexibile MIDI I/O
  • DIN 5 Plug
  • or 3.5mm Mini TRS Plug
  • and/or Header Pins for wiring off-board plug
  • USB Midi

Power Supply

Flexible power supply options

• 6-28V Power input to connect to usual pedalboard power supply units.
  • 3A DC-DC buck converter
  • Also powers MIDI module
• MIDI module can also be powered with USB power.
  • Supports ORing with the onboard PSU.

Generated Hardware Documentation

Interactive KiCanvas viewer.

Downloadable Assets are generated with KiBot

Fabrication

• Generated iBOM
• Digi-Key shared list
• PCBWay manifacturing
• For detailed build instruction follow the wiki

3D Views

Mechanical Parts

3D printable parts can be found in the pedalboard-case project.

References

• HifiBerry DAC/ADC+
• PIHat Mechanical Spec

How to release

see Release Procedure