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

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)

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

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.

Modules