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ATMegaZero ESP32-S2
Raspberry Pi Zero–style ESP32-S2 board - ideal for Linux-style form factor with secure IoT power.
65 × 30 mm
ESP32-S2
MCU
240MHz
clock
16MB
flash
320KB
SRAM
24· 6 ADC
GPIO
Wi-Fi
radio
Pinout
24 pins · 2.54 mm pitch| Pin | GPIO | Labels | Status | Capabilities | Notes |
|---|---|---|---|---|---|
| 1 | 0 | PD5 | strapping | - | |
| 2 | 1 | T1PWM | safe | touch | |
| 3 | 2 | T2PWM | safe | touch | |
| 4 | 3 | A5T3PWM | safe | adc · touch | |
| 5 | 4 | T4PWM | safe | touch | |
| 6 | 5 | T5PWM | safe | touch | |
| 7 | 6 | A4T6PWM | safe | adc · touch | |
| 8 | 7 | T7PWM | safe | touch | |
| 9 | 8 | SDAT8PWM | safe | touch · i2c | |
| 10 | 9 | SCLT9PWM | strapping | touch · i2c | |
| 11 | 10 | T10PWM | strapping | touch | |
| 12 | 11 | T11PWM | strapping | touch | |
| 13 | 12 | A3T12PWM | strapping | adc · touch | |
| 14 | 13 | A2T13PWM | strapping | adc · touch | |
| 15 | 14 | T14PWM | strapping | touch | |
| 16 | 17 | A0DAC1PWM | safe | adc · dac | |
| 17 | 18 | A1DAC2PWM | safe | adc · dac | |
| 18 | 35 | MOSIPWM | strapping | spi | |
| 19 | 36 | SCKPWM | strapping | spi | |
| 20 | 37 | MISOPWM | strapping | spi | |
| 21 | 38 | SSPWM | strapping | spi | |
| 22 | 40 | NEOPIXELPWM | strapping | - | |
| 23 | 43 | TXPWM | uart | uart | |
| 24 | 44 | RXPWM | uart | uart |
Start with these
12 pins with no boot or system involvementT1PWMT2PWMA5T3T4PWMT5PWMA4T6T7PWMSDAT8A0DAC1A1DAC2TXPWMRXPWM
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 |
|---|---|---|---|
| PD5 | GPIO0 | Must be pulled high for normal boot; pulling low at reset enters bootloader (download mode). Also serves as SPI flash data-in (SPID) line when using external flash memory. | Strapping |
| NEOPIXEL | MTDO | Part of JTAG interface (TDO); should be avoided as GPIO if JTAG debugging is needed. | Other |
Only if you know the tricks
wired to flash or USB - expect a fight| Pin | Label | What to know | Role |
|---|---|---|---|
| SCL | FSPIHD | Typically used as flash/PSRAM IO line in certain configurations; avoid using as GPIO if flash or PSRAM is present. | Flash |
| T10 | FSPICS0 | Often used as flash chip select in some designs; not available for GPIO when controlling flash. | Flash |
| T11 | FSPID | Used for flash data transfer in certain configurations; should be avoided for general use if flash is connected. | Flash |
| A3 | FSPICLK | Used as flash clock line in some boards; not free for GPIO if driving flash. | Flash |
| A2 | FSPIQ | Used for flash data output in certain configurations; avoid using as GPIO if connected to flash. | Flash |
| T14 | FSPIWP | Used as flash write-protect/data line on some modules; not recommended for other usage. | Flash |
| MOSI | FSPID | Used by internal flash/PSRAM on some ESP32-S2 variants; avoid using as GPIO to prevent conflicts. | Flash |
| SCK | FSPICLK | May be connected to internal flash or used for high-speed SPI; not intended for general GPIO use. | Flash |
| MISO | FSPIQ | Used for internal flash/PSRAM data in some models; should not be repurposed for GPIO. | Flash |
| SS | FSPIWP | Reserved for flash/PSRAM in ESP32-S2 modules with internal memory; not recommended for general I/O. | 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 ATMegaZero ESP32-S2 pinout brings out 24 GPIO pins at a 2.54 mm pitch - every one of them usable in your project. For peripherals, I²C is mapped to SDA on…
The ATMegaZero ESP32-S2 pinout brings out 24 GPIO pins at a 2.54 mm pitch - every one of them usable in your project.
For peripherals, I²C is mapped to SDA on GPIO8 and SCL on GPIO9; the SPI bus (MOSI, MISO, SCK, SS) is broken out in full; TX/RX on GPIO43 and GPIO44 cover serial logging and flashing.
On the analog side there are 6 ADC-capable pins for sensors and battery monitoring, 14 capacitive-touch inputs and 2 true DAC outputs.
If you want zero surprises, T1, T2, A5, T4 and 8 more are free of any such role - the safest first picks. 2 of the exposed pins carry boot-time or system duties on the ESP32-S2 (PD5 and NEOPIXEL).
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: "ESP32S2 Dev Module"▸
USB CDC On Boot: "Enabled"▸
Flash Size: "16MB (128Mb)"▸
Flash Mode: "QIO"▸
PSRAM: "QSPI PSRAM"▸
Partition Scheme: "16M Flash (3MB APP / 9.9MB FATFS)" (default)▸
Upload Speed: "921600"▸
▸ every other Tools option — leave at default
Board: ESP32S2 Dev Module USB CDC On Boot: Enabled Flash Size: 16MB (128Mb) Flash Mode: QIO PSRAM: QSPI PSRAM Partition Scheme: 16M Flash (3MB APP / 9.9MB FATFS) Upload Speed: 921600
Find it: Tools ▸ Board ▸ ESP32 Arduino ▸ ESP32S2 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-s2-saola-1⧉ copy
[env:atmegazero_esp32s2]
platform = espressif32
board = esp32-s2-saola-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-s2-saola-1 — or type it after board =.board to selectesp32-s2-saola-1⧉ copy
esp32:
board: esp32-s2-saola-1
variant: atmegazero_esp32s2
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-s2-saola-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 esp32s2 --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 · QIO
Specifications
ESP32-S2 · 65 × 30 mmCompute
MCU
ESP32-S2
Clock
240 MHz
SRAM · Flash
320 KB · 16MB · 8MB (QSPI) PSRAM
Radio
Wi-Fi
802.11 b/g/n 2.4 GHz
Bluetooth
-
Antenna
PCB
I/O
GPIO · ADC
24 · 6
UART · I²C · SPI
2 · 1 · 4
PWM
8 channels
Power
USB
Micro-USB (native) · Micro-USB (native)
Serial
Native (CDC)
Boot address
0x1000
Flashing
Upload · OTA
esptool_py · esp_ota
Flash · Boot mode
QIO · QIO
Sketch · Data
1.25 MB · 320 KB
65 × 30 mm · pin pitch 2.54 mm
The ATMegaZero ESP32-S2 uses esptool_py for firmware uploads, esp_ota for over-the-air (OTA) updates. Flash mode is QIO 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-S2 - a single-core Xtensa with native USB-OTG and no Bluetooth.
Expect to pay about $24.99 - above the ~$20 typical for ESP32-S2 boards.
Onboard you'll find 8MB (QSPI) PSRAM, a microSD slot, an addressable RGB LED (GPIO40) and Reset buttons.
It flashes over native USB - no serial-converter driver needed, which isn't a given among ESP32-S2 boards.
- Raspberry Pi Zero form factor with 40-pin GPIO header
- 30-pin FPC OLED display port for SSD1306/SH1106 displays (not included)
- 3D antenna for 2.4GHz Wi-Fi
- 4x onboard status LEDs
Where to buy
prices are typical street pricesATMegaZero ESP32-S2
$24.99per unit, typical
Resources
ESP32-S2 datasheet espressif.com↗ ATMegaZero official site atmegazero.com↗ATMegaZero ESP32-S2 on GroupGets (specs & pricing) archive.groupgets.com↗ATMegaZero ESP32-S2 board supports OLED displays (CNX Software) cnx-software.com↗ATMegaZero ESP32-S2 CircuitPython board circuitpython.org↗arduino-esp32 atmegazero_esp32s2 variant github.com↗
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