ESP32 Multi-Track MIDI Breadboard Instrument

An embedded polyphonic buzzer synthesizer and OLED visualizer running on a dual-core ESP32 (ESP-IDF v5.2.2, FreeRTOS). Melodies are parsed from standard .mid files using a Python run-length encoding script (scripts/midi_to_c.py) into C struct arrays stored in flash.

Hardware Pinout

Component	ESP32 GPIO	Notes
Passive Buzzer (Melody)	GPIO 25	Driven by hardware LEDC PWM timer
Active Buzzer 1 (Kick)	GPIO 26	Percussion trigger output
Active Buzzer 2 (Hi-Hat)	GPIO 27	Percussion trigger output
LED 1 (Kick Indicator)	GPIO 21	Active on kick trigger
LED 2 (Hi-Hat Indicator)	GPIO 22	Active on hi-hat trigger
Rotary Encoder CLK / DT / SW	GPIO 32 / 33 / 16	Hardware PCNT quadrature decoding; button toggles volume/tempo mode
Play / Pause Button	GPIO 13	Active-low input with internal pull-up
Next Track Button	GPIO 14	Cycles through the 16-track array
1.3" SPI OLED (SH1106)	CS: 5, DC: 2, RES: 4, MOSI: 23, SCK: 18	128x64 display rendered from Core 0

Software Structure

• main/mmcontroller.c — FreeRTOS application splitting UI rendering (oled_visualizer_task on Core 0) and audio timing (buzzer_sequence_task on Core 1).
• scripts/midi_to_c.py — Python utility (mido) that converts MIDI note events into C SequenceStep arrays ({frequency, duration, kick_drum, hi_hat}).
• images/ — Breadboard wiring and OLED operation photos.

Building and Flashing

source ~/esp/esp-idf/export.sh
idf.py set-target esp32
idf.py build
idf.py -p /dev/ttyUSB0 flash monitor

To convert a MIDI file into a C array:

python3 scripts/midi_to_c.py scripts/midillis/Alla_Turca/Alla_Turca.mid > track_output.h