Hardware

The firmware runs on any ESP32-S3 board with at least 4 MB of Octal PSRAM. The reference build targets the ESP32-S3-WROOM-1-N16R8 dev kit.

Bill of materials

Component	Part	Notes
MCU	ESP32-S3-WROOM-1-N16R8	16 MB flash, 8 MB Octal PSRAM
DAC	PCM5102A	I²S stereo DAC (we feed L=R mono)
Mic	INMP441	I²S MEMS mic, left channel
Display	2.4″ TFT ILI9341	240×320, SPI
Buttons	23× 6 mm tact	16 in a 4×4 scan matrix + 7 PO-33 modifiers
Status LEDs	2× 3 mm LED	REC + PLAY indicators
Power	USB-C 5 V	Or single-cell LiPo + TP4056
Optional amp	MAX98357A	I²S class-D amp for built-in speaker

Pin map

All pins below are configured in main/config.h. Edit there if your board differs.

Audio (PCM5102A + INMP441)

DAC BCLK	GPIO9
DAC LRCK	GPIO10
DAC DIN	GPIO8
Mic BCLK	GPIO15
Mic LRCK	GPIO16
Mic DOUT	GPIO17

2.4″ TFT (ILI9341 SPI)

MOSI	GPIO6
SCK	GPIO7
CS	GPIO5
DC	GPIO4
RST	GPIO48
BL (PWM)	GPIO47

Buttons — matrix + modifiers

23 buttons: 16 step buttons on a 4×4 scan matrix (btn_id = BTN_STEP1 + row × 4 + col) plus 7 PO-33 modifier keys on their own GPIOs. Internal pull-ups everywhere.

Matrix rows	GPIO35, 36, 37, 38
Matrix cols	GPIO33, 34, 39, 40
SOUND	GPIO11
PATTERN	GPIO44
BPM	GPIO13
REC	GPIO41
FX	GPIO12
PLAY	GPIO42
WRITE	GPIO43

Knobs (ADC)

Two 10 kΩ linear pots, read on ADC1 and debounced in software.

Knob A	GPIO20 / ADC1_CH9
Knob B	GPIO46 / ADC1_CH5

Sync + LEDs

Sync OUT	GPIO18
Sync IN	GPIO19
LED REC	GPIO21
LED PLAY	GPIO14

Power

The firmware draws ~10 µA in deep sleep, so a 1500 mAh LiPo will last ~6 months on standby. Active power depends on which voice engine is running; expect 60–120 mA at moderate polyphony.

The 5-minute idle timer drops the chip into deep sleep automatically. Any button press wakes it back up — via a GPIO interrupt on the matrix column pins or on any of the seven modifier GPIOs.