S1Vave — 8-Voice Virtual Analog Tweak Synth for M-VAVE FM-1

S1Vave is an open-source firmware that transforms the portable M-VAVE FM-1 synthesizer hardware (JieLi AC791N 32-bit RISC MCU) into an 8-voice virtual analog tweak synth modeled after the classic SH-101 and S-1 architecture.

Every aspect—from the classic oscillator core and sub-oscillator waveshapes, to the cascaded 4-pole filter with self-oscillation, calibrated ADSR envelope curves, unique OSC DRAW and OSC CHOP sound manipulation, multi-waveform LFO with audio-rate Fast mode, stereo effects suite, and 1:1 MIDI CC implementation—has been modeled and calibrated to provide complete sound engine parity.

S1Vave on the M-VAVE FM-1: PTN 1-01, PERFORM page with CUTOFF, RESO, ENV AMT, PORTA T, real-time scope, 7-segment display, and 8-voice LEDs

Highlights & Features

1. Classic SH-101 Voice Architecture & Tweak Innovations

Polyphony & Voicing Modes (8-Voice Engine):
- MONO: True SH-101 monosynth with legato glide (auto-portamento).
- UNISON: 8-voice stacked unison with massive analog lead and bass presence.
- POLY: 8-voice dynamic polyphony for rich chords and lush pads.
- CHORD: Programmable chord memory with independent voice shifts (-12 to +12 semitones).
Oscillator Core:
- Sawtooth: PolyBLEP anti-aliased classic saw.
- Square / Pulse: Wide-range Pulse Width Modulation (PWM) from 50% square down to ~5% needle pulse. Modulated via Manual duty cycle, Envelope sweep, or LFO.
- Sub-Oscillator: 3 authentic octave types:
  - -2o.A: 2 octaves below, 25% asymmetric duty cycle (signature SH-101 growl).
  - -2oc: 2 octaves below, 50% symmetric square wave.
  - -1oc: 1 octave below, 50% symmetric square wave.
- Noise Generator: Calibrated Pink Noise (analog 12 dB/oct roll-off above 1.8 kHz) and White Noise.
Unique Wave-Shaping Features:
- OSC DRAW: 16-step wavetable drawing (STEP mode for raw digital textures or SLOPE for smooth interpolated waves), with a 1.0x to 32.0x frequency multiplier.
- OSC CHOP: Harmonic comb slicing (1.0 to 32.0 repetitions) with overtone depth control (0–200, $>100$ phase inverted) to create metallic overtones and bell-like timbres.
- Riser / Downer: Built-in performance transition sweep generator (SYNC, QUIV, and QV.PAN modes) for sweeping rises, risers, and dropouts.

2. Cascaded 4-Pole Filter & Calibrated Envelopes

4-Pole (24 dB/oct) Cascaded State-Variable Filter:
- Full $20\text{ Hz} \dots 20\text{ kHz}$ calibrated cutoff curve matching the S-1 hardware pot response.
- Smooth analog resonance with self-oscillation and bass retention.
- Keyboard tracking ($0% \dots 100%$) and bipolar filter envelope modulation.
- Dual filter character modes: S-1 Clean Roland ACB and Warm Midnight soft-knee drive.
Calibrated ADSR Envelopes:
- Precise exponential analog RC attack, decay, sustain, and release curves measured from the Roland S-1 hardware.
- Envelope trigger modes: GATE, GATE+TRIG (re-triggers on overlapping notes), and LFO (cyclic re-triggering).
- Amp envelope mode: Instant GATE (organ style) or dynamic ENV (ADSR shaped).

3. Modulation & Effects

Versatile LFO Engine:
- 6 Waveforms: Sawtooth, Inverted Sawtooth, Triangle, Square, Random (S&H), and Noise.
- Speed range: $0.05\text{ Hz} \dots 30\text{ Hz}$ in Normal mode, and up to $\sim 100\text{ Hz}$ in Fast audio-rate mode.
- Tempo Sync: Locked to MIDI clock across 31 musical note divisions ($8/1$ to $1/128$ triplets/dotted).
- Key Trigger: Option to reset LFO phase on note-on.
Stereo FX Suite:
- Stereo Chorus: 4 chorus models (Type 1–4) with Hermite-interpolated delay lines.
- Tempo-Synced Delay: Stereo ping-pong delay with analog tape slewing when changing delay time and feedback tone filtering.
- Plate Reverb: High-density Dattorro figure-of-8 reverberator running at the full 44.1 kHz sample rate (7 room types: Ambient, Room, Hall 1, Hall 2, Plate, Spring, Mod).

4. Sequencer, Presets & USB Connectivity

Dual-Track 64-Step Sequencer:
- Two polyphonic tracks (A and B) sharing 256 steps with independent length, clock division, swing, and transpose for complex polymeters.
- Step entry with piano roll view, live recording, sub-step ratchets (1–4), per-step probability, and motion recording.
- 8 pattern slots saved directly in flash memory.
99 Presets & Instant Recall:
- Programs 1–64 come pre-loaded with authentic factory sounds and patterns; slots 65–99 are available for user programs.
- Startup recall sequence preserves custom OSC DRAW wavetables and OSC CHOP comb masks.
- Direct bidirectional SysEx patch dump & restore support over USB-MIDI.
Enhanced Arpeggiator & Hold:
- Press and hold ARP button (450 ms) to toggle HOLD latch mode instantly.
- Dedicated Arp page (Mode, Hold, Type, Rate) and Arp Config page (Note Priority: Low / Last).
- Seamless key release and retrigger behavior in latch/hold mode.
Dynamic Battery Level Monitoring:
- Real-time SARADC battery tracking with 4-bar hysteresis and visual low-voltage blinking alert in the status bar header.
S-1 Parity Velocity & Key Follow:
- Dynamic velocity sensitivity scaling for VCA amplitude (~18 dB musical dynamic range).
- True 1V/oct chromatic filter keyboard tracking (scaled to Q8 semitones).
USB-Audio & Class-Compliant USB-MIDI:
- 44.1 kHz / 16-bit stereo USB Audio with zero-glitch ring buffering.
- Complete 1:1 MIDI Control Change implementation chart.

Hardware Panel Controls (M-VAVE FM-1)

The M-VAVE FM-1 has 4 push-encoders (K1–K4), 8 function buttons, and 16 step keys. Tapping any button brings up its page:

Page / Button	KNOB 1 (`K1`)	KNOB 2 (`K2`)	KNOB 3 (`K3`)	KNOB 4 (`K4`)
HOME (PERFORM)	Cutoff (FREQ) `[CC 74]`	Resonance (RESO) `[CC 71]`	Env Depth (ENV) `[CC 24]`	Portamento Time `[CC 5]`
EDIT (OSC CORE)	Range (64'..2') `[CC 14]`	Square Level `[CC 19]`	Saw Level `[CC 20]`	Sub Level `[CC 21]`
EDIT (PWM)	PWM Source `[CC 16]`	Pulse Width / Duty `[CC 15]`	Square Level `[CC 19]`	Sub Octave Type `[CC 22]`
EDIT (SUB/NOISE)	Sub Type (`-2o.A`, `-2oc`, `-1oc`)	Noise Level `[CC 23]`	Noise Mode (Pink/White)	Fine Tune `[CC 76]`
EDIT (OSC DRAW)	Draw Switch (Off/Step/Slope)	Multiply (1.0x–32.0x)	PWM Source `[CC 16]`	Pulse Width `[CC 15]`
EDIT (OSC CHOP)	Chop Overtone (0–200) `[CC 103]`	Chop Comb (1.0–32.0) `[CC 104]`	—	—
EDIT (FILTER)	Filter Cutoff `[CC 74]`	Filter Resonance `[CC 71]`	Filter LFO Depth `[CC 25]`	Key Follow (0–100%) `[CC 26]`
ENV (ADSR)	Attack `[CC 73]`	Decay `[CC 75]`	Sustain `[CC 30]`	Release `[CC 72]`
ENV (TRIG/AMP)	Env Trigger Mode `[CC 29]`	Amp Mode (Gate/Env) `[CC 28]`	PWM Source `[CC 16]`	PWM Depth `[CC 15]`
LFO (CORE)	LFO Rate `[CC 3]`	Waveform `[CC 12]`	Tempo Sync `[CC 106]`	Fast Mode `[CC 79]`
LFO (ROUTING)	Pitch LFO Depth `[CC 13]`	Filter LFO Depth `[CC 25]`	PWM Depth `[CC 15]`	Key Trigger `[CC 105]`
LFO (RISER)	Riser Mode (Sync/Quiv/Pan)	Riser Resonance	Riser Shape	Riser Level
FX (MIX)	Chorus Mode `[CC 93]`	Delay Level `[CC 92]`	Reverb Level `[CC 91]`	Delay Time `[CC 90]`
FX (DELAY)	Delay Level `[CC 92]`	Delay Time `[CC 90]`	Delay Feedback	Delay Tempo Sync
FX (REVERB)	Reverb Level `[CC 91]`	Reverb Time `[CC 89]`	Reverb Type (Plate..Mod)	Chorus Mode `[CC 93]`
GLO (VOICE)	Poly Mode (Mono..Chord) `[CC 80]`	Portamento Mode `[CC 31]`	Transpose `[CC 77]`	Master Volume `[CC 7]`

For the full button layer combinations, arpeggiator operations, and step sequencer instructions, see the Hardware Panel Guide.

Complete MIDI CC Implementation

S1Vave maps parameters 1:1 to the S-1 MIDI specification:

CC 1: Mod Wheel (LFO Depth)
CC 3: LFO Rate
CC 5: Portamento Time
CC 12: LFO Waveform
CC 13: OSC Pitch LFO Depth
CC 14: OSC Range (64'..2')
CC 15: PWM Depth / Pulse Width
CC 16: PWM Source (0=ENV, 1=MAN, 2=LFO)
CC 19: Square/Pulse Level
CC 20: Saw Level
CC 21: Sub Level
CC 22: Sub Octave Type (0=-2o.A, 1=-2oc, 2=-1oc)
CC 23: Noise Level
CC 24: Filter Env Depth
CC 25: Filter LFO Depth
CC 26: Filter Key Tracking
CC 28: Amp Env Mode (0=Gate, 1=Env)
CC 29: Env Trigger Mode (0=LFO, 1=Gate, 2=Gate+Trig)
CC 30: Envelope Sustain
CC 31: Portamento Mode (0=Off, 1=On, 2=Auto)
CC 71: Filter Resonance
CC 72: Envelope Release
CC 73: Envelope Attack
CC 74: Filter Cutoff Frequency
CC 75: Envelope Decay
CC 76: Fine Tune
CC 77: Key Transpose
CC 78: Noise Mode (0=Pink, 1=White) / Riser Mode
CC 79: LFO Speed Mode (0=Normal, 1=Fast)
CC 80: Poly Mode (0=Mono, 1=Unison, 2=Poly, 3=Chord)
CC 89: Reverb Time
CC 90: Delay Time
CC 91: Reverb Level
CC 92: Delay Level
CC 93: Chorus Mode (0=Off, 1..4=Type 1..4)
CC 102: OSC DRAW Multiply (1.0x–32.0x)
CC 103: OSC CHOP Overtone (0–200)
CC 104: OSC CHOP Comb (1.0–32.0)
CC 105: LFO Key Trigger (0=Off, 1=On)
CC 106: LFO Tempo Sync (0=Off, 1=On)
CC 107: OSC DRAW Switch (0=Off, 1=Step, 2=Slope)

For the comprehensive MIDI CC list and value ranges, see the MIDI CC Implementation Guide.

Flashing & Installation

Option 1: Quick Install via Python (Recommended)

Connect your M-VAVE FM-1 via USB-C to your computer:

python tools/fm1_install.py build/s1vave-1.1.fwsc --yes

The script communicates over USB HID, validates checksums, flashes the firmware sector by sector (~2 minutes), and automatically reboots the hardware into S1Vave.

Option 2: Web Installer

You can also install S1Vave with one click via WebUSB / WebMIDI on thefirmwarehub.com.

Browser Simulator & Web Calibration Studio

Experience the firmware directly in your web browser with the WebAssembly simulation:

Build the WebAssembly binary:
```
sh web/sim/build.sh
```

Start the local server:

python3 -m http.server 8737 -d docs/sim

Open http://localhost:8737/ to interact with the virtual LCD, encoders, buttons, and play notes from your computer or MIDI keyboard.
Open http://localhost:8737/editor/ to access the Dual Synth Calibration Studio for side-by-side A/B acoustic comparisons.

Building from Source (Linux / WSL2)

1. Prerequisites

sudo apt update
sudo apt install -y python3 python3-pip git build-essential pipewire alsa-utils
pip3 install Pillow mido python-rtmidi

2. Download Toolchain

cd s1vave-main
./tools/get_toolchain.sh

3. Clone JieLi AC79 SDK

git clone --depth 1 --branch AC79NN_SDK_V1.2.1_2023-12-13 https://gitee.com/Jieli-Tech/fw-AC79_AIoT_SDK.git ~/fw-AC79_AIoT_SDK

4. Compile Firmware Package

./build.sh --release 1.1

The build pipeline enforces strict JieLi AC791N hardware rules (integer-only fixed-point DSP, prohibition of 64-bit software divisions, and ROM collision prevention). The resulting .fwsc firmware binary will be placed at build/s1vave-1.1.fwsc.

Documentation Links

Technical Handover & Calibration Guide: Deep dive into the DSP equations, fixed-point math, acoustic calibration measurements, volume staging, and USB audio buffer watermarks.
Hardware Panel & Navigation Guide: Complete guide to all physical knobs, buttons, layers, and sequencer views.
MIDI CC Implementation Chart: Complete reference of all supported MIDI Control Changes.
JieLi AC791N Hardware Rules: Architectural and compiler rules for developing firmware on the AC791N RISC MCU.
Licensing & Credits: Upstream credits, contributors, and open-source licenses.

Credits & License

S1Vave is free software released under the GNU General Public License v3.0 (GPL-3.0-only). See LICENSE and LICENSING.md.

Parity Sound Engine, DSP Calibration & Visual Branding: Andrew GG
OberVave Synthesizer & Dinghy Platform: zvenson (original OberVave codebase and Dinghy platform wiring)
Felucca Base Platform: Leo Kuroshita (@kurogedelic), Hügelton Instruments
SLOOP Platform Contributions: isod89
SMK-37 Port: M. Geisler

Roland, AIRA, AIRA Compact, S-1, and SH-101 are trademarks of Roland Corporation. M-VAVE, FM-1, and SMK-37 are trademarks of Shenzhen Sincoo Technology Co., Ltd. S1Vave is an independent community project and is not affiliated with or endorsed by Roland Corporation or Shenzhen Sincoo Technology Co., Ltd.