Drumboy Main

Drumboy Pro

📖 Developer Wiki — full hardware specs, schematics walkthrough, firmware architecture, DSP internals, and memory map.

An open-source hardware groovebox — sequencer, sampler, and DSP effects engine built around an STM32H723 (Cortex-M7 @ 550 MHz), with a 540×960 touch-free color display, 42 keys, 8 rotary encoders, and full MIDI/Sync I/O.

This repository holds the complete hardware design (KiCad) and firmware (STM32CubeIDE / C++) for Drumboy Pro, released by Randomwaves as an open hardware/software project.

Overview

The MCU sits at the center of six subsystems: an NT35510 display driven over a 16-bit parallel GPIO bus, 16 MB of external SDRAM for sample streaming, an SGTL5000 audio codec over I2S/I2C, a microSD card for storage, a control surface fanned out over six MCP23017 I/O expanders, and external connectivity (MIDI, Sync, USB-C power).

Features

• 10 sample layers, each independently modulated by a 10-slot LFO matrix (sample-and-hold at note-trigger time)
• Per-layer routing into a shared DSP chain: parametric EQ → 2× multimode filter → 2× send effect → stereo reverb
• 9 effect types per send slot: Delay, Chorus, Flanger, Phaser, Compressor, Expander, Overdrive, Distortion, Bitcrusher
• Freeverb/Schroeder-Moorer style reverb with pre-delay and stereo surround derivation
• Sequencer with 5 song banks per layer, 64 beats per bank, and algorithmic complex-fill generation (timing alignment × level curve templates)
• MIDI In/Out (opto-isolated input) and Sync In/Out for external clock/gate sync
• SD-card firmware updates via a dedicated bootloader with CRC-32 verified staged writes
• Fully open hardware (KiCad) and firmware (C/C++ against the STM32 HAL) — no CMSIS-DSP or external DSP library, all hand-rolled biquad/delay-line DSP on the Cortex-M7 FPU

Repository structure

01 Hardware/
  Main/       KiCad project — main board (Drumboy_Main)
  Top/        KiCad project — top/control-surface board (Drumboy_Top)
  Drawing/    Mechanical drawings, enclosure models, graphics, fonts

02 Software/
  Drumboy-Pro-Boot-H723/   Bootloader — STM32CubeIDE project (own repo, linked below)
  Drumboy-Pro-App-H723/    Application firmware — STM32CubeIDE project (own repo, linked below)
  Firmware/                 Prebuilt firmware binaries
  Sd Card/                  Reference SD card contents (samples, presets, drumkits, system data)

Related repositories

Firmware is split into two independently-built projects that share one flash device — a bad application build can never brick the update path:

Hardware

Designed in KiCad 7. Open 01 Hardware/Main/Drumboy_Main.kicad_pro for the main board, or 01 Hardware/Top/Drumboy_Top.kicad_pro for the control-surface board. All third-party symbols, footprints, and 3D models are vendored under each project's Library/ folder.

Mechanical design (enclosure and 3D model) lives in 01 Hardware/Drawing/ as Rhinoceros 8 files — Drumboy Pro 2D.3dm and Drumboy Pro 3D.zip (zipped to keep it under GitHub's file size limit; unzip to get the .3dm).

A full BOM is generated from KiCad at production/bom.csv. See the wiki for the annotated schematic walkthrough, clock tree, power-domain isolation scheme, and key component reference.

Firmware

Built with STM32CubeIDE, written in C/C++ against the STM32 HAL.

• Bootloader owns flash sector 0 (0x08000000–0x0801FFFF)
• Application owns sectors 1–7 (0x08020000–0x080FFFFF), with the vector table relocated at startup

To flash over SWD, wire an ST-Link V2 to the board's SWDIO (PA13), SWCLK (PA14), and GND pins, then build and flash from STM32CubeIDE. See the wiki's Build, Flash & Debug section for details.

License

Released under the MIT License.

Community

• 💬 Discord community — join the discussion
• 🌐 randomwaves.io
• ✉️ hello@randomwaves.io