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smk37-firmware-custom-mod

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M-VAVE SMK-37 Pro Custom Firmware Mods (Woovebox 3.0 BLE-MIDI & Low-Latency DAW Fixes), Flasher Tools, and Dedicated ASIO Driver

smk37-firmware-custom-mod is custom firmware for the M-VAVE SMK-37 Pro and M-VAVE SMK-37 Elite, by @amalahama. Open source under MIT, latest release v022 (October 2026), 11 stars on GitHub.

forM-VAVE SMK-37 Pro,M-VAVE SMK-37 Elite·by@amalahama

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Download v022

SMK-37_Pro_custom_022.fwsc· 689 KB· +3 files

MIT· amalahama/smk37-firmware-custom-mod·downloads come from the creator’s GitHub releases

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M-VAVE SMK-37 Pro Custom Firmware & BLE/ASIO Mods

Release License: MIT

Custom firmware modifications, architecture documentation, Windows flasher tool, and dedicated ASIO driver for the M-VAVE SMK-37 Pro MIDI controller keyboard (JieLi AC791N SoC).

🚀 Quick Start / Flashing v022

To update your SMK-37 Pro to custom firmware v022 (resolves Woovebox 3.0 BLE-MIDI pairing/notes and DAW stability):

  1. Download the latest release package: SMK-37_Pro_custom_v022_flasher.zip
  2. Extract the ZIP folder.
  3. Connect your SMK-37 Pro to your PC via USB cable and close all DAWs/MIDI software.
  4. Run flash_v022.bat (or run python smk_ota_win.py flash SMK-37_Pro_custom_022.fwsc).

1. Project Objectives

  1. BLE MIDI Stability with Woovebox 3.0: Enable Woovebox 3.0 (ESP32-based hardware synthesizer in hoSt bLE / 4/Ar mode) to reliably discover, pair, and maintain a rock-solid, low-latency BLE-MIDI connection with the SMK-37 Pro, transmitting notes continuously without dropouts or frozen states.
  2. Dedicated Low-Latency Windows ASIO Driver: Optimize the SMK-37 Pro as a USB Audio Class 1.0 (UAC1) interface and MIDI controller on Windows, achieving true low latency (< 4-6 ms roundtrip) via a dedicated ASIO driver with a circular FIFO ring buffer that eliminates buffer overruns and DAW crashes (CTD).

2. Technical Diagnostics & Root Cause Analysis

  • Hardware Platform: JieLi AC791N / WL82 SoC (Dual-Core pi32v2 CPU @ 240-320MHz).
  • Base Firmware: Stock image SMK-37_Pro_016.fwsc (version 1.16).
  • JLFS Encryption: JieLi SFC cipher with chipkey 0x980F (38927) and header key 0xFFFF.
  • Root Causes of Incompatibility with Woovebox 3.0 (ESP32 Host):
    1. Concurrent Secondary Advertising: When the host subscribed to BLE-MIDI notifications (CCCD 0x2902), the stock firmware launched secondary advertising bursts on RF channels 37/38/39, confusing the ESP32 host scanner and causing connection loops.
    2. Rigid Supervision Timeout: The stock 1,000 ms supervision timeout dropped connections upon minor RF jitter or FreeRTOS task scheduling delays on the ESP32.
    3. SMP Authentication Rejection: The stock stack demanded MITM / Passkey Display pairing, causing headless embedded hosts without displays or keypads to time out.
    4. CCCD Gate on Note Dispatch: Routine 0x02000AD4 silently dropped MIDI note packets if the host didn't re-write CCCD 0x2902 upon reconnecting to an already bonded link.
    5. NVS Stale Bond Cache Collision: The keyboard cached its static MAC address in flash VM key 102. If the host retained a broken or incomplete security record for that address, reconnects hung indefinitely.
  • Complete Solution: Custom Firmware v022 surgically patches these 5 architectural flaws at the pi32v2 machine code level while preserving 100% backward compatibility with USB MIDI, desktop DAWs, and the official M-VAVE mobile app.

3. Repository Structure

  • release/: Flashable binaries, batch scripts, and the pre-packaged SMK-37_Pro_custom_v022_flasher.zip.
  • tools/:
    • repack_smk.py: Automated unpacker, patcher, and SFC re-encryptor for .fwsc containers.
    • unpack_smk.py: De-interleaves 36-block extended containers and extracts JLFS/UFW components.
    • smk_ota_win.py: Zero-dependency Windows USB-MIDI SysEx OTA flasher.
    • jltech/: Self-contained JieLi encryption, CRC, and cipher package.
  • stock_firmware/: Reference stock firmware v016 (SMK-37_Pro_016.fwsc).
  • firmware_work/: Verified custom firmware builds (v017 through v022).
  • BLE_EXTENDED_PATCH.txt: Complete technical specification and assembly-level reference for all applied BLE patches.
  • driver_asio/: Dedicated 64-bit native Windows ASIO COM driver (SMK37Pro_ASIO.dll), control panel GUI (SMK37Pro_ControlPanel.exe), automated tests, and installation scripts.
  • docs/: In-depth firmware architecture, reverse-engineered function maps, and Woovebox setup guides.
  • PLAN.md: Milestone progress roadmap.

4. Current Development Status

✅ Custom Firmware v022 (Verified & Fully Functional with Woovebox 3.0)

  • Production Binary: firmware_work/SMK-37_Pro_custom_022.fwsc (SHA-256: fe51c1c6eba90dc9aabe40900457aa1c1ddb3d9c32391335b1aceaded1d2035f).
  • Surgical Assembly Patches Applied:
    1. Secondary Advertising Suppression (Offset 0x0013D2): Unconditional jump bypassing multi-slot advertising triggers during active connections.
    2. Connection Parameters Relaxation (Offset 0x05839E): Increased supervision timeout to 4,000 ms with flexible intervals (7.5-20 ms / 15-30 ms).
    3. SMP "Just Works" Bonding (Offsets 0x087446, 0x08758A, 0x0875C4): Configured auth_req = 0x01 (Bonding without MITM), IO_CAP = 3 (NoInputNoOutput), and removed mandatory Secure Connections for full BLE 4.0/4.2 compatibility.
    4. Unconditional BLE-MIDI Notifications (Offset 0x000AEE): NOPs the CCCD check, guaranteeing MIDI note packets are transmitted even if the host Central skips re-writing descriptor 0x2902.
    5. Clean Unique MAC Generation (Offsets 0x0035CE, 0x003668): Redirects Flash VM MAC key from 102 to 108, generating a fresh Bluetooth address to clear stale host bond records.
    6. Version Bump to v022 & Checksum Integrity: Recalculated all JLFS/UFW CRC16s, re-encrypted with SFC chipkey 0x980F, and updated container trailer markers.
  • Full Architecture Guide: BLE_EXTENDED_PATCH.txt.

✅ USB MIDI Subsystem & DAW Integration (Verified)

  • Direct WinMM Verification: Dynamic velocity response (25-93) verified across all 37 keys with clean Note On (0x90) and Note Off (0x80) on Channel 1 without stuck notes or dropped packets.
  • DAW Compatibility: Verified with Ableton Live, Reaper, FL Studio, and Logic Pro.

✅ Dedicated Ultra-Low Latency ASIO Driver (driver_asio)

  • Architecture: User-mode COM InProc server (SMK37Pro_ASIO.dll, CLSID {7C38B80E-5AED-4B33-A751-6CE34EC4C701}).
  • Circular FIFO Ring Buffer: Prevents buffer underruns and DAW crashes (CTD), ensuring pristine, continuous audio playback.
  • WASAPI Exclusive Engine: Direct communication with USB Audio Class 1.0 endpoints (2-in / 2-out, 24-bit PCM, 44.1 kHz), bypassing the Windows audio engine.
  • Ultra-Low Latency: Configurable buffer sizes from 32 samples (0.73 ms) to 2048 samples (46.4 ms).
  • Real-Time MMCSS Thread: MMCSS "Pro Audio" scheduling with ping-pong double buffering.
  • Control Panel: Native Win32 GUI accessible directly via DAW Hardware Setup / Control Panel buttons or as a standalone executable (bin/SMK37Pro_ControlPanel.exe).