M5Stack-ATOM
Ultra-compact ESP32 board with RGB LED and button - ideal for simple wireless triggers and automation nodes.
M5Stack-ATOM Pinout
19 pins
| Pin | GPIO | Labels | Status | Capabilities | Notes |
|---|---|---|---|---|---|
| 1 | 0 | G0 | strapping | - | |
| 2 | 1 | TXPWM | uart | uart | |
| 3 | 3 | RXPWM | uart | uart | |
| 4 | 9 | G9PWM | strapping | - | |
| 5 | 10 | G10PWM | strapping | - | |
| 6 | 12 | G12PWM | strapping | - | |
| 7 | 19 | G19SSPWM | safe | spi | |
| 8 | 21 | G21PWM | safe | - | |
| 9 | 22 | G22SCKPWM | safe | spi | |
| 10 | 23 | G23MISOPWM | safe | spi | |
| 11 | 25 | G25DAC1PWM | safe | dac | |
| 12 | 26 | RXD2SDAG26DAC2PWM | safe | i2c · dac | |
| 13 | 27 | G27PWM | safe | - | |
| 14 | 32 | TXD2SCLG32PWM | safe | i2c | |
| 15 | 33 | G33MOSIPWM | safe | spi | |
| 16 | 35 | ADC1 | strapping | - | |
| 17 | 36 | G36ADC2 | strapping | - | |
| 18 | 37 | G37 | strapping | - | |
| 19 | 39 | G39 | strapping | - |
Start with these
9 pins with no boot or system involvementFreely assignable - no strapping, flash, USB or JTAG duties. Ideal first picks for buttons, sensors and LEDs.
Fine - with a little care
8 pins · 6 things to knowG0GPIO0 Bootstrapping pin (enter bootloader when low); internal pull-up. Strapping
Must be HIGH during boot for normal startup; if held LOW on reset, forces flash programming mode.
TXGPIO1 Default UART0 TX pin for USB-serial programming and console. UART
Connected to on-board USB-UART for uploading and logs; drives serial output at boot, so using as GPIO can disrupt programming or console.
RXGPIO3 Default UART0 RX pin for USB-serial programming (console input). UART
Used for receiving data from USB-UART (programming); also pulled HIGH at boot for console communication, so using as GPIO can disrupt uploads.
G12GPIO12 Bootstrapping pin; JTAG TDI; sets flash voltage (VDD_SDIO); also HSPIQ (flash data line). Strapping
Keep LOW during boot (internal PD); pulling HIGH at reset selects 1.8V flash mode, causing flash brownout if 3.3V flash is used.
ADC1GPIO35G37GPIO37G39GPIO39 Input-only GPIOs with ADC1 channels - no output driver Other
Cannot be used as output; only suitable for input.
- ADC1Input-only GPIO (no output driver); ADC1 channel 7.
- G37Input-only GPIO (no output); ADC1 channel 1.
- G39Input-only GPIO (no output); ADC1 channel 3, Hall sensor VN.
G36GPIO36 Input-only GPIO (no output); ADC1 channel 0, Hall sensor VP. Other
Cannot be used as output; only suitable for input (e.g., analog read).
Only if you know the tricks
2 pins · 1 thing to knowG9GPIO9G10GPIO10 SPI flash/PSRAM data lines SD2 and SD3 (flash HOLD and WP) Flash
Used by internal flash/PSRAM; typically not exposed on modules, avoid using as GPIO.
- G9Connected to SPI flash/PSRAM data 2 (SD2, flash HOLD).
- G10Connected to SPI flash/PSRAM data 3 (SD3, flash WP).
The M5Stack-ATOM pinout brings out 19 GPIO pins - every one of them usable in your project.
For peripherals, I²C is mapped to SDA on GPIO26 and SCL on GPIO32; the SPI bus (MOSI, MISO, SCK, SS) is broken out in full; TX/RX on GPIO1 and GPIO3 cover serial logging and flashing.
On the analog side there are 2 true DAC outputs.
If you want zero surprises, G19, G21, G22, G23 and 5 more are free of any such role - the safest first picks. 8 of the exposed pins carry boot-time or system duties on the ESP32 (G0, TX, RX and 5 more).
Getting started
flash your first firmware in ~2 minutesBoard: ESP32 Dev Module Flash Size: 4MB (32Mb) Flash Mode: DIO Partition Scheme: Default 4MB with spiffs (1.2MB APP/1.5MB SPIFFS) Upload Speed: 921600
// toggle GPIO19 - wire an LED and resistor to it
void setup() {
pinMode(19, OUTPUT);
}
void loop() {
digitalWrite(19, HIGH); delay(500);
digitalWrite(19, LOW); delay(500);
}[env:m5stack-atom]
platform = espressif32
board = esp32dev
framework = arduino
monitor_speed = 115200
upload_speed = 921600esp32dev - or type it after board =.esp32:
board: esp32dev
variant: esp32
framework:
type: esp-idf
# blink - GPIO19
output:
- platform: gpio
pin: 19
id: led_out
light:
- platform: binary
name: "LED"
output: led_outesp32dev (same ids as PlatformIO).esptool.py --chip esp32 --port /dev/ttyACM0 \
--baud 921600 write_flash 0x1000 firmware.bin--port = your /dev/tty* (macOS/Linux) or COMx (Windows).Specifications
ESP32 · 24 × 24 mm · vs other ESP32 chips →Dimensions
About this board
At its core is the ESP32 - a dual-core Xtensa with both Bluetooth Classic and BLE.
Expect to pay about $7.50 - less than the ~$20 most ESP32 boards go for.
Only 19 GPIO are broken out, where most ESP32 boards manage about 24 - worth checking the pinout covers what you need.
Onboard you'll find a Grove connector, an addressable RGB LED (GPIO27), an IR transceiver and User buttons.
Where to buy
prices are typical street pricesResources
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