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LOLIN S2 Mini
Compact ESP32-S2 board by Wemos with USB-C in a small castellated form factor - great for space-saving embedded builds.
34.3 × 25.4 mm
ESP32-S2
MCU
240MHz
clock
4MB
flash
320KB
SRAM
27· 14 ADC
GPIO
Wi-Fi
radio
Pinout
30 pins · 2.54 mm pitch
| Pin | GPIO | Labels | Status | Capabilities | Notes |
|---|---|---|---|---|---|
| 1 | - | 5V | power | - | 5V power input for the board |
| 2 | - | GND | ground | - | Ground connection |
| 3 | - | 3V33.3V | power | - | 3.3V power output |
| 4 | 1 | IO1GPIO1 | safe | - | GPIO |
| 5 | 2 | IO2GPIO2 | safe | adc | GPIO, ADC |
| 6 | 3 | IO3GPIO3 | safe | - | GPIO |
| 7 | 4 | IO4GPIO4 | safe | adc | GPIO, ADC |
| 8 | 5 | IO5GPIO5 | safe | - | GPIO |
| 9 | 6 | IO6GPIO5 | safe | - | GPIO |
| 10 | 7 | IO7GPIO5 | safe | - | GPIO |
| 11 | 8 | IO8GPIO5 | safe | - | GPIO |
| 12 | 9 | IO9GPIO5 | strapping | - | GPIO |
| 13 | 10 | IO10GPIO5 | strapping | - | GPIO |
| 14 | 11 | IO11GPIO5 | strapping | - | GPIO |
| 15 | 12 | IO12GPIO12 | strapping | adc | GPIO, ADC |
| 16 | 13 | IO13GPIO13 | strapping | adc | GPIO, ADC |
| 17 | 14 | IO14GPIO14 | strapping | adc | GPIO, ADC |
| 18 | 15 | IO15GPIO15 | strapping | adc | GPIO, ADC |
| 19 | 16 | IO16GPIO16 | strapping | - | GPIO |
| 20 | 17 | IO17GPIO17 | safe | - | GPIO |
| 21 | 18 | IO18GPIO18 | safe | - | GPIO |
| 22 | 21 | IO21GPIO21 | safe | - | GPIO |
| 23 | 33 | IO33GPIO33 | strapping | adc | GPIO, ADC |
| 24 | 34 | IO34GPIO34 | strapping | adc | GPIO, ADC |
| 25 | 35 | IO35GPIO35 | strapping | adc | GPIO, ADC |
| 26 | 36 | IO36GPIO36 | strapping | adc | GPIO, ADC |
| 27 | 37 | IO37GPIO37 | strapping | adc | GPIO, ADC |
| 28 | 38 | IO38GPIO38 | safe | adc | GPIO, ADC |
| 29 | 39 | IO39GPIO39 | strapping | adc | GPIO, ADC |
| 30 | 40 | IO40GPIO40 | strapping | adc | GPIO, ADC |
Start with these
12 pins with no boot or system involvementIO1GPIO1IO2GPIO2IO3GPIO3IO4GPIO4IO5GPIO5IO6GPIO5IO7GPIO5IO8GPIO5IO17GPIO17IO18GPIO18IO21GPIO21IO38GPIO38
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 |
|---|---|---|---|
| IO9 | FSPIHD | IO MUX pin of the general-purpose SPI2 (FSPI) bus, not of the in-package flash - that sits on GPIO26-32. The datasheet does not restrict it, so it is only taken if your board wires flash, an SD card or a display to FSPI. | Other |
| IO10 | FSPICS0 | IO MUX pin of the general-purpose SPI2 (FSPI) bus, not of the in-package flash - that sits on GPIO26-32. The datasheet does not restrict it, so it is only taken if your board wires flash, an SD card or a display to FSPI. | Other |
| IO11 | FSPID | IO MUX pin of the general-purpose SPI2 (FSPI) bus, not of the in-package flash - that sits on GPIO26-32. The datasheet does not restrict it, so it is only taken if your board wires flash, an SD card or a display to FSPI. | Other |
| IO12 | FSPICLK | IO MUX pin of the general-purpose SPI2 (FSPI) bus, not of the in-package flash - that sits on GPIO26-32. The datasheet does not restrict it, so it is only taken if your board wires flash, an SD card or a display to FSPI. | Other |
| IO13 | FSPIQ | IO MUX pin of the general-purpose SPI2 (FSPI) bus, not of the in-package flash - that sits on GPIO26-32. The datasheet does not restrict it, so it is only taken if your board wires flash, an SD card or a display to FSPI. | Other |
| IO14 | FSPIWP | IO MUX pin of the general-purpose SPI2 (FSPI) bus, not of the in-package flash - that sits on GPIO26-32. The datasheet does not restrict it, so it is only taken if your board wires flash, an SD card or a display to FSPI. | Other |
| IO15 | XTAL_32K_P | If an external 32 kHz crystal is used for RTC, this pin is dedicated to the crystal and cannot be used as GPIO. | Other |
| IO16 | XTAL_32K_N | If using an external 32 kHz crystal, this pin is connected to the crystal and should not be used as general I/O. | Other |
| IO39 | MTCK | Used for JTAG debugging interface; using this pin for other purposes will disable JTAG clock input. | Other |
| IO40 | 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 |
|---|---|---|---|
| IO33 | SPIIO4 (GPIO33) | The datasheet keeps GPIO33-37 for "the higher 4 bits data line interface and DQS interface for the SPI0/1 interface in 8-line SPI mode, and can be GPIO pins if the chip is not connected to flash or PSRAM in 8-line SPI mode". Quad-SPI parts leave it free. | Flash |
| IO34 | SPIIO5 (GPIO34) | The datasheet keeps GPIO33-37 for "the higher 4 bits data line interface and DQS interface for the SPI0/1 interface in 8-line SPI mode, and can be GPIO pins if the chip is not connected to flash or PSRAM in 8-line SPI mode". Quad-SPI parts leave it free. | Flash |
| IO35 | SPIIO6 (GPIO35) | The datasheet keeps GPIO33-37 for "the higher 4 bits data line interface and DQS interface for the SPI0/1 interface in 8-line SPI mode, and can be GPIO pins if the chip is not connected to flash or PSRAM in 8-line SPI mode". Quad-SPI parts leave it free. | Flash |
| IO36 | SPIIO7 (GPIO36) | The datasheet keeps GPIO33-37 for "the higher 4 bits data line interface and DQS interface for the SPI0/1 interface in 8-line SPI mode, and can be GPIO pins if the chip is not connected to flash or PSRAM in 8-line SPI mode". Quad-SPI parts leave it free. | Flash |
| IO37 | SPIDQS (GPIO37) | The datasheet keeps GPIO33-37 for "the higher 4 bits data line interface and DQS interface for the SPI0/1 interface in 8-line SPI mode, and can be GPIO pins if the chip is not connected to flash or PSRAM in 8-line SPI mode". Quad-SPI parts leave it free. | 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 LOLIN S2 Mini pinout brings out 30 pins at a 2.54 mm pitch - 27 usable GPIO alongside the 5V, GND and 3V3 power rails. On the analog side there are 14…
The LOLIN S2 Mini pinout brings out 30 pins at a 2.54 mm pitch - 27 usable GPIO alongside the 5V, GND and 3V3 power rails.
On the analog side there are 14 ADC-capable pins for sensors and battery monitoring.
If you want zero surprises, IO1, IO2, IO3, IO4 and 8 more are free of any such role - the safest first picks. 10 of the exposed pins carry boot-time or system duties on the ESP32-S2 (IO9, IO10, IO11 and 7 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
GPIO1 toggles - wire an LED and resistor to it, or change the pin to your board's own LED.
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: "4MB (32Mb)"▸
Flash Mode: "DIO"▸
PSRAM: "QSPI PSRAM"▸
Partition Scheme: "Default 4MB with spiffs (1.2MB APP/1.5MB SPIFFS)" (default)▸
Upload Speed: "921600"▸
▸ every other Tools option - leave at default
Board: ESP32S2 Dev Module USB CDC On Boot: Enabled Flash Size: 4MB (32Mb) Flash Mode: DIO PSRAM: QSPI PSRAM Partition Scheme: Default 4MB with spiffs (1.2MB APP/1.5MB SPIFFS) Upload Speed: 921600
Find it: Tools ▸ Board ▸ ESP32 Arduino ▸ ESP32S2 Dev Module
// toggle GPIO1 - wire an LED and resistor to it
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:lolin_s2_mini]
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: 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 0x1000 firmware.bin--port = your /dev/tty* (macOS/Linux) or COMx (Windows).Build details: sketch space 1310720 B · data 327680 B · DIO
Specifications
ESP32-S2 · 34.3 × 25.4 mm · vs other ESP32 chips →Compute
MCU
ESP32-S2
Clock
240 MHz
SRAM · Flash
320 KB · 4MB · 2MB PSRAM
Radio
Wi-Fi
802.11 b/g/n 2.4 GHz
Bluetooth
-
Antenna
PCB
I/O
GPIO · ADC
27 · 14
UART · I²C · SPI
2 · 2 · 2
PWM
8 channels
Power
USB
USB-C
Serial
Native (CDC)
Boot address
0x1000
Electrical
Input
-
Consumption
-
Regulator
ME6211C33
Flashing
Upload · OTA
esptool_py · esp_ota
Flash · Boot mode
DIO · QIO
Sketch · Data
1.25 MB · 320 KB
34.3 × 25.4 mm · pin pitch 2.54 mm
The LOLIN S2 Mini 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-S2 - a single-core Xtensa with native USB-OTG and no Bluetooth.
Expect to pay about $5.00 - less than the ~$20 most ESP32-S2 boards go for.
Onboard you'll find 2MB PSRAM, status LEDs (Blue (GPIO15)) and Reset/Button (GPIO0) buttons.
It flashes over native USB - no serial-converter driver needed, which isn't a given among ESP32-S2 boards.
Where to buy
prices are typical street pricesAs an Amazon Associate, ESPboards earns from qualifying purchases.
Resources
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