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M5Stack-ATOMS3
A compact ESP32-S3 development kit by M5Stack, suitable for rapid prototyping and IoT applications.
24 × 24 mm
ESP32-S3
MCU
240MHz
clock
8MB
flash
512KB
SRAM
21· Two 12-bit, 20 Channels ADC
GPIO
BLE 5.0+ WiFi
radio
Pinout
22 pins
| Pin | GPIO | Labels | Status | Capabilities | Notes |
|---|---|---|---|---|---|
| 1 | 0 | G0 | strapping | - | |
| 2 | 1 | TXD2G1PWM | safe | - | |
| 3 | 2 | RXD2G2PWM | safe | - | |
| 4 | 3 | G3PWM | strapping | - | |
| 5 | 4 | G4PWM | safe | - | |
| 6 | 5 | G5PWM | safe | - | |
| 7 | 6 | G6PWM | safe | - | |
| 8 | 7 | G7ADC1PWM | safe | - | |
| 9 | 8 | G8ADC2PWM | safe | - | |
| 10 | 15 | SSPWM | safe | spi | |
| 11 | 17 | SCKPWM | safe | spi | |
| 12 | 21 | MOSIPWM | safe | spi | |
| 13 | 36 | G36PWM | strapping | - | |
| 14 | 37 | G37PWM | strapping | - | |
| 15 | 38 | SDAG38PWM | strapping | i2c | |
| 16 | 39 | SCLG39PWM | strapping | i2c | |
| 17 | 40 | G40PWM | strapping | - | |
| 18 | 42 | G42PWM | strapping | - | |
| 19 | 43 | TXPWM | strapping | uart | |
| 20 | 44 | RXPWM | strapping | uart | |
| 21 | 48 | LED_BUILTIN | strapping | - | |
| 22 | - | MISO | safe | spi |
Start with these
10 pins with no boot or system involvementTXD2G1RXD2G2G4PWMG5PWMG6PWMG7ADC1G8ADC2SSPWMSCKPWMMOSIPWM
Freely assignable - no strapping, flash, USB or JTAG duties. Ideal first picks for buttons, sensors and LEDs.
Fine - with a little care
sampled at boot or shared with debug/serial| Pin | Label | What to know | Role |
|---|---|---|---|
| G0 | GPIO0 | Must be pulled high (default) or low (to enter UART download mode) at reset. Using it for other functions can interfere with boot mode configuration. | Strapping |
| G3 | GPIO3 | Sampled at reset to select JTAG interface (USB Serial/JTAG controller vs. external pins). Improper use can disable external JTAG or alter debug interface. | Strapping |
| SCL | MTCK (GPIO39) | Default JTAG debugging TCK pin. If JTAG is needed, this pin must be free; it may also be used internally for PSRAM chip select on certain modules, so avoid repurposing it. | Other |
| G40 | MTDO (GPIO40) | Default JTAG TDO output for debugging. Using it as GPIO will interfere with JTAG debugging functionality. | Other |
| G42 | MTMS (GPIO42) | Default JTAG TMS signal for debugging. Using this pin for other purposes will disable the JTAG interface (unless JTAG is rerouted to USB). | Other |
| TX | U0TXD (GPIO43) | Used for bootloader output and UART console logs. If repurposed, you will lose the default serial output (and programming via UART0). | Other |
| RX | U0RXD (GPIO44) | Used for bootloader input (download mode via serial). If repurposed, you cannot use the default UART0 download mode for programming the chip. | Other |
Only if you know the tricks
wired to flash or USB - expect a fight| Pin | Label | What to know | Role |
|---|---|---|---|
| G36 | FSPICLK / PSRAM_CLK | In modules with octal PSRAM, this pin drives the PSRAM clock. It must be dedicated to the memory interface, not used as a regular GPIO when that interface is in use. | Flash |
| G37 | FSPIQ / PSRAM_DQS | In modules with octal PSRAM, this pin is connected to the PSRAM’s DQS signal. It cannot be repurposed without disrupting the PSRAM/flash communication. | Flash |
| SDA | FSPIWP | On flash-equipped chips, this pin is tied to the flash’s WP# (or D3) line. It should be avoided for other use, as it’s needed for flash operations. | Flash |
| LED_BUILTIN | SPICLK_N | Used only on variants with Octal SPI interface, as the negative leg of the differential clock&. On such chips it operates at 1.8 V; it should be avoided for GPIO to prevent conflicts with the octal flash/PSRAM clock. | Flash |
These are recommendations, not hard rules - with the right pull-ups, timing and boot-state awareness most pins can be made to work. When in doubt, start green.
Pinout notes The M5Stack-ATOMS3 pinout brings out 22 pins - 21 usable GPIO. For peripherals, I²C is mapped to SDA on GPIO38 and SCL on GPIO39; the SPI bus ( MOSI , MISO ,…
The M5Stack-ATOMS3 pinout brings out 22 pins - 21 usable GPIO.
For peripherals, I²C is mapped to SDA on GPIO38 and SCL on GPIO39; the SPI bus (MOSI, MISO, SCK, SS) is broken out in full; TX/RX on GPIO43 and GPIO44 cover serial logging and flashing.
If you want zero surprises, TXD2, RXD2, G4, G5 and 6 more are free of any such role - the safest first picks. 7 of the exposed pins carry boot-time or system duties on the ESP32-S3 (G0, G3, SCL and 4 more).
Getting started
flash your first firmware in ~2 minutes1
Connect over USB
Native USB - shows up as a port right away, no driver needed. Not detected? Hold BOOT while plugging in.
2
Match & flash
Set the Tools options shown, then click Upload.
3
Verify it runs
The onboard LED on GPIO1 blinks - swap the pin if your board's LED differs.
Set these in Tools · leave everything else at default
Arduino IDE 2.x — Tools Copy
Board: "ESP32S3 Dev Module"▸
USB CDC On Boot: "Enabled"▸
Flash Size: "8MB (64Mb)"▸
Flash Mode: "DIO"▸
PSRAM: "QSPI PSRAM"▸
Partition Scheme: "8M with spiffs (3MB APP / 1.5MB SPIFFS)" (default)▸
Upload Speed: "921600"▸
▸ every other Tools option — leave at default
Board: ESP32S3 Dev Module USB CDC On Boot: Enabled Flash Size: 8MB (64Mb) Flash Mode: DIO PSRAM: QSPI PSRAM Partition Scheme: 8M with spiffs (3MB APP / 1.5MB SPIFFS) Upload Speed: 921600
Find it: Tools ▸ Board ▸ ESP32 Arduino ▸ ESP32S3 Dev Module
// blink the onboard LED
void setup() {
pinMode(1, OUTPUT);
}
void loop() {
digitalWrite(1, HIGH); delay(500);
digitalWrite(1, LOW); delay(500);
}board to selectesp32-s3-devkitc-1⧉ copy
[env:m5stack-atoms3]
platform = espressif32
board = esp32-s3-devkitc-1
framework = arduino
monitor_speed = 115200
upload_speed = 921600
board_build.arduino.memory_type = qio_qspi
build_flags = -DBOARD_HAS_PSRAMFind it: PlatformIO Home ▸ Boards, search
esp32-s3-devkitc-1 — or type it after board =.board to selectesp32-s3-devkitc-1⧉ copy
esp32:
board: esp32-s3-devkitc-1
variant: m5stack_atoms3
framework:
type: esp-idf
psram:
mode: quad
speed: 80MHz
# blink - GPIO1
output:
- platform: gpio
pin: 1
id: led_out
light:
- platform: binary
name: "LED"
output: led_outFind it: search ESPHome's board list for
esp32-s3-devkitc-1 (same ids as PlatformIO).esptool doesn't pick board settings — a prebuilt .bin already has them baked in. This is just the raw flash command.
esptool.py --chip esp32s3 --port /dev/ttyACM0 \
--baud 921600 write_flash 0x0 firmware.bin--port = your /dev/tty* (macOS/Linux) or COMx (Windows).Build details: sketch space 1310720 B · data 327680 B · DIO
Specifications
ESP32-S3 · 24 × 24 mmCompute
MCU
ESP32-S3
Clock
240 MHz
SRAM · Flash
512 KB · 8MB
Radio
Wi-Fi
802.11 b/g/n
Bluetooth
5.0 LE
Antenna
3D
I/O
GPIO · ADC
21 · Two 12-bit, 20 Channels
UART · I²C · SPI
3 · 2 · 4
PWM
8 channels
Power
USB
USB-C
Serial
Native (CDC)
Boot address
0x0
Display
Screen
IPS LCD · 0.85" · 128x128
Driver
GC9107
Touch
No
Flashing
Upload · OTA
esptool_py · esp_ota
Flash · Boot mode
DIO · QIO
Sketch · Data
1.25 MB · 320 KB
24 × 24 mm
The M5Stack-ATOMS3 uses esptool_py for firmware uploads, esp_ota for over-the-air (OTA) updates. Flash mode is DIO with QIO boot mode. The maximum sketch size is 1.25 MB with 320 KB available for data.
About this board
At its core is the ESP32-S3 - a dual-core Xtensa with vector extensions suited to AI workloads.
Expect to pay about $15.50 - less than the ~$30 most ESP32-S3 boards go for.
Onboard you'll find an IPS LCD 0.85" 128x128 display, a Grove connector, an MPU6886 IMU, an IR transceiver and Screen buttons.
It flashes over native USB - no serial-converter driver needed, which isn't a given among ESP32-S3 boards.
Where to buy
prices are typical street pricesResources
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