Boardm5stack

M5Stack AtomS3

M5Stack AtomS3 (C123): a 24x24 mm ESP32-S3 board with a 0.85-inch GC9107 LCD (MOSI G21, SCK G17, CS G15, RS G33, RST G34, BL G16), an MPU6886 IMU at 0x68 sharing the I2C bus on IO38=SDA / IO39=SCL, two bottom edge columns (J3 left: 3V3/G5/G6/G7/G8; J4 right: G39/G38/5V/GND) and one HY2.0-4P port (J6).

Assembly & compatibility

Main chip: ESP32-S3

Revisions

Current production board — Single current revision; v1 is an internal ordering id. · M5Stack AtomS3 product documentation (pin map tables, schematics PDF, datasheet) · Sch_M5_AtomS3_v1.0.pdf

Pinout

power · ground · GPIO / signal · onboard LED

Bottom edge, left device-pad column (official PinMap orientation): 3V3 / G5 / G6 / G7 / G8 (5 pins)

The page text says 'The bottom reserves 6 GPIO and power pins for easy expansion'; the image pins the order. · Source: M5Stack AtomS3 product documentation (pin map tables, schematics PDF, datasheet) · M5Stack AtomS3 official PinMap image, bottom edge left column; schematic connector J3

No.	Name	Type	GPIO	Function
1	3V3	P		3.3 V output
2	G5	I/O	5	Free GPIO
3	G6	I/O	6	Free GPIO
4	G7	I/O	7	Free GPIO
5	G8	I/O	8	Free GPIO

Bottom edge, right device-pad column (official PinMap orientation): G39 / G38 / 5V / GND (4 pins)

G39/G38 double as the MPU6886 I2C bus: page text 'The I2C pins on the back share the same bus IO38 SDA IO39 SCL'. · Source: M5Stack AtomS3 product documentation (pin map tables, schematics PDF, datasheet) · M5Stack AtomS3 official PinMap image, bottom edge right column; schematic connector J4

No.	Name	Type	GPIO	Function
1	G39	I/O	39	Free GPIO; shares the IMU I2C bus as SCL
2	G38	I/O	38	Free GPIO; shares the IMU I2C bus as SDA
3	5V	P		5 V from USB
4	GND	G		Ground

HY2.0-4P port (PORT.C / BLACK), schematic connector J6, schematic pin order 1-4 = G1 / G2 / 5V / GND (4 pins)

Table numbers are the schematic pin positions. Reading the mating wire side (plug key up, left to right) the colors run White = G1 (J6.1), Yellow = G2 (J6.2), Red = 5V (J6.3), Black = GND (J6.4) - the same pins in mirrored order · Source: M5Stack AtomS3 product documentation (pin map tables, schematics PDF, datasheet) · docs.m5stack.com/en/core/AtomS3 pin map table (HY2.0-4P / PORT.CUSTOM row)

No.	Name	Type	GPIO	Function
1	G1	I/O	1	GPIO1; PORT.C black-shell signal 1
2	G2	I/O	2	GPIO2; PORT.C black-shell signal 2
3	5V	P		5 V supply
4	GND	G		Ground

The AtomS3 (SKU C123) is M5Stack's 24 x 24 mm ESP32-S3 square: a 0.85-inch 128x128 GC9107 LCD on the top face, an MPU6886 IMU (I2C 0x68) underneath, one HY2.0-4P connector (Black GND / Red 5V / Yellow G2 / White G1) and a USB-C port. The screen is why this board's GPIO budget is unusual: MOSI=G21, SCK=G17, CS=G15, RS=G33, RST=G34 and backlight=G16 are all occupied by the LCD.

Count the rest in two groups. Exclusively free: G5, G6, G7, G8 on the bottom edge (left column, top-to-bottom 3V3 / G5 / G6 / G7 / G8 per the official PinMap image) and G1 / G2 on the HY2.0-4P port — the port and the edge pads are two separate contact groups. Shared: the right edge column reads G39 / G38 / 5V / GND top-to-bottom, and G38/G39 are the IMU's I2C bus — the page states the back-side pins share one bus, IO38=SDA and IO39=SCL, so use them as GPIO or your own I2C only with the IMU traffic in mind. Exactly which pins are yours is answered in What is actually free on the AtomS3?.

This page renders the MCUID data record: the edge columns (J3 left: 3V3/G5/G6/G7/G8; J4 right: G39/G38/5V/GND), the HY2.0-4P port (schematic connector J6, pin order G1/G2/5V/GND — the wire side reads mirrored), the LCD and free-GPIO tables, and each fact tied to the M5Stack documentation.