Digital Oscillators • Modular Patching • Low-Cost DSP Platform
This project transforms three Arduino UNO boards into a fully modular digital synthesizer, powered by the Mozzi audio synthesis library. The goal was to explore lo-fi digital sound, microcontroller DSP, and modular patchability — all with accessible hardware.
System Concept
Each Arduino serves as a separate synth module, each with its own dedicated voice function:
| Module | Function | Outputs |
|---|---|---|
| UNO #1 | Main VCO + Sub-Oscillator | Audio, Sync |
| UNO #2 | LFO + Envelope Generator | CV Modulation |
| UNO #3 | Digital Filter + FX Stage | Audio Out |
Data and modulation signals are shared through analog CV lines, allowing real patching between modules — just like Eurorack, but on DIY microcontrollers.
Mozzi DSP Core
All audio and modulation is generated in real-time using Mozzi, running at 16 kHz sample rate.
Features include:
- PWM audio output → analog filtered
- Wavetable + FM oscillators
- Envelope shaping
- Mod routing with lookup tables
Custom waveforms were loaded for gritty digital tones:
- Saw / Square / Triangle / Noise
- Experimental bit-crushed waves
- Detuned dual-osc mode
Control & Interface
Each board includes:
- 3–5 CV-responsive parameters
- 2–3 Potentiometers on the panel
- Patchable CV In / CV Out mini jacks
- An Audio Out with RC filtering
Manual controls + CV = hybrid performance workflow.
Modular Patchability
Signals can be cross-patched:
- VCO → Digital Filter → FX
- LFO → Pitch / Cutoff / PWM
- EG → Volume / FM Depth
The system behaves like a small desktop modular — knobs, patch cables, LEDs animating with the sound.
Extra Touches
- Interrupt-based timing for tight oscillation
- Quantized pitch tables for melodic patterns
- Low-latency control smoothing to reduce stepping
- Panel designed with a clean micro-modular layout
Sound Character
✨ Raw digital texture with analog shaping
✅ Great FM, chiptune leads, rhythmic modulation artifacts
💥 Filters add unstable, musical distortion at high resonance
The imperfections of a small microcontroller become part of the sound — noisy, punchy, expressive.