lucky-cat/docs/gpio-map.md

ESP32-S3 GPIO Map

This document defines the active firmware GPIO assignments for the current battery-sensing ESP32-S3 board revision. Signal direction is described from the MCU's perspective. Older 2026-07-24 drawings assigned GPIO9 to a legacy power hold net; that assignment is not valid for the current board.

GPIO Table

U5 Pin	GPIO	Net	Direction	Connection / Function	Notes
1	GND	GND	N/A	Ground reference	Ground reference
2	3V3	3V3	Power	3.3 V supply rail	Power rail
3	EN/RST	EN	Input	Chip enable and reset input	Reset and enable
4	GPIO4	TP_INT	Bidirectional	Optional touch interrupt / reusable IO	Not connected by the 8-wire LCD adapter
5	GPIO5	TP_SDA	Bidirectional	Optional touch I2C SDA / reusable IO	Not connected by the 8-wire LCD adapter
6	GPIO6	TP_SCL	Input	Rocker microswitch / original SW2 function	Reuses the touch-clock contact left open by the 8-wire LCD adapter; active-low with internal pull-up
7	GPIO7	BLK	Output	LCD adapter backlight control	Active-high firmware default
8	GPIO15	CS	Output	ST7789P3 SPI chip select	Active low
9	GPIO16	DC	Output	ST7789P3 data/command select	Also named A0 by the panel specification
10	GPIO17	RES	Output	ST7789P3 hardware reset	Active low
11	GPIO18	MOSI	Output	ST7789P3 SPI data / SDA	4-line SPI write data
12	GPIO8	CLK / Swing	Output	ST7789P3 SPI clock	Do not drive the Swing function while the LCD is connected
13	GPIO19	ESP_D_N	Bidirectional	USB D-	Type-C
14	GPIO20	ESP_D_P	Bidirectional	USB D+	Type-C
15	GPIO3	touch	Input	TTP223 touch-button output	Present on the board but not consumed by the current input policy
16	GPIO46	UNASSIGNED	N/A	No connection assigned	Reserved; no signal assigned
17	GPIO9	Power_t	Analog input	Battery voltage sense	R17=100 kOhm from VBAT and R18=100 kOhm to GND; ADC voltage is one half of VBAT
18	GPIO10	Charge	Input	TP4057 charger status	Active-low while charging; high means full or external power absent
19	GPIO11	PA_CTRL	Output	Audio power-amplifier enable	Amplifier control
20	GPIO12	SW1	Input	Button 1 / turntable calibration switch	External 10 kOhm pull-up; active low
21	GPIO13	SW2	Input	Button 2 / K2 push-to-talk input	External 10 kOhm pull-up; active low
22	GPIO14	UNASSIGNED	N/A	No connection assigned	Reserved; no signal assigned
23	GPIO21	IN4	Output	ULN2003 IN4	Stepper motor phase control
24	GPIO47	IN3	Output	ULN2003 IN3	Stepper motor phase control
25	GPIO48	IN2	Output	ULN2003 IN2	Stepper motor phase control
26	GPIO45	IN1	Output	ULN2003 IN1	Stepper motor phase control
27	GPIO0	BOOT	Input	Boot/download switch	10 kOhm pull-up to 3V3
28	GPIO35	UNASSIGNED	N/A	No connection assigned	Reserved; no signal assigned
29	GPIO36	UNASSIGNED	N/A	No connection assigned	Reserved; no signal assigned
30	GPIO37	UNASSIGNED	N/A	No connection assigned	Reserved; no signal assigned
31	GPIO38	I2S_MCLK	Output	ES8311 MCLK	Audio interface
32	GPIO39	I2S_SCLK	Output	ES8311 SCLK	Audio interface
33	GPIO40	I2S_DSDIN	Output	ES8311 DSDIN	Audio interface
34	GPIO41	I2S_LRCK	Output	ES8311 LRCK	Audio interface
35	GPIO42	I2S_ASDOUT	Input	ES8311 ASDOUT	Audio interface
36	RXD0	esp_tx	Input	Debug UART	Routed to J2
37	TXD0	esp_rx	Output	Debug UART	Routed to J2
38	GPIO2	IO2_I2C_SCL	Bidirectional	ES8311 control interface SCL	Audio codec
39	GPIO1	IO1_I2C_SDA	Bidirectional	ES8311 control interface SDA	Audio codec
40	GND	GND	N/A	Ground reference	Ground reference
41	GND	GND	N/A	Ground reference	Ground reference