A compact polyphonic synthesizer built on the ESP32-S3 platform.
It combines a dedicated Input chip for UI and MIDI handling, and an Audio chip for real-time voice synthesis and audio output.

---

System Architecture

🟢 Audio Chip — ESP32-S3

The Audio chip is responsible for generating sound.
It receives MIDI and control events via I²C from the Input chip, synthesizes voices, and outputs audio via I²S to a PCM5102 DAC.

Main components:

• Voices (3):
  Each voice has:
  • Oscillators (Sine, Square, Triangle, Noise)
  • ADSR envelope
  • Filter with cutoff/resonance
  • Modulation: Pitch LFO and Amp LFO
• Render loop: Combines all voices and applies modulation
• Mix + I²S output to PCM5102 DAC
• Master volume knob and noise filtering stage on analog output

---

🟣 Input Chip — ESP32-S3

The Input chip handles user interaction, display, and incoming MIDI, and sends events over I²C to the Audio chip.

Main components:

• Knob + Button: User input for menu navigation and voice settings
• Display: Shows menus and settings
• USB MIDI In: Receives external MIDI notes and clock
• BPM counter: Generates BPM events from MIDI clock
• I²C Sender: Sends voice settings, BPM events, and MIDI notes to the Audio chip

---

Signal Flow

Control path:
Knob/Button → Menu/Settings → I²C → Audio Chip

MIDI path:
USB MIDI → BPM counter + MIDI events → I²C → Audio Chip

Audio path:
Voices → Render loop → Mix → I²S → PCM5102 → Analog Output

---

Status

This is an active work-in-progress project.
Follow development on GitHub: esp32-audio-synth