No
No
N/A
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 | strapping | adc | GPIO, ADC |
| 29 | 39 | IO39GPIO39 | strapping | adc | GPIO, ADC |
| 30 | 40 | IO40GPIO40 | strapping | adc | GPIO, ADC |
Start with these
11 pins with no boot or system involvementIO1GPIO1IO2GPIO2IO3GPIO3IO4GPIO4IO5GPIO5IO6GPIO5IO7GPIO5IO8GPIO5IO17GPIO17IO18GPIO18IO21GPIO21
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 |
|---|---|---|---|
| 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 |
|---|---|---|---|
| IO9 | FSPIHD | Typically used as flash/PSRAM IO line in certain configurations; avoid using as GPIO if flash or PSRAM is present. | Flash |
| IO10 | FSPICS0 | Often used as flash chip select in some designs; not available for GPIO when controlling flash. | Flash |
| IO11 | FSPID | Used for flash data transfer in certain configurations; should be avoided for general use if flash is connected. | Flash |
| IO12 | FSPICLK | Used as flash clock line in some boards; not free for GPIO if driving flash. | Flash |
| IO13 | FSPIQ | Used for flash data output in certain configurations; avoid using as GPIO if connected to flash. | Flash |
| IO14 | FSPIWP | Used as flash write-protect/data line on some modules; not recommended for other usage. | Flash |
| IO33 | SPIHD | Connected to SPI flash (hold/data line); not available for general-purpose use. | Flash |
| IO34 | SPIWP | Connected to SPI flash (write-protect/data line); not recommended for other use. | Flash |
| IO35 | FSPID | Used by internal flash/PSRAM on some ESP32-S2 variants; avoid using as GPIO to prevent conflicts. | Flash |
| IO36 | FSPICLK | May be connected to internal flash or used for high-speed SPI; not intended for general GPIO use. | Flash |
| IO37 | FSPIQ | Used for internal flash/PSRAM data in some models; should not be repurposed for GPIO. | Flash |
| IO38 | 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 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 7 more are free of any such role - the safest first picks. 4 of the exposed pins carry boot-time or system duties on the ESP32-S2 (IO15, IO16, IO39 and 1 more).
Getting started
flash your first firmware in ~2 minutes1
Connect over USB
Native USB - no driver, no serial chip. Not detected? Hold BOOT while plugging in.
2
Flash with your tool
Arduino IDE, PlatformIO, ESPHome or esptool - copy the settings on the right.
3
Verify it runs
The blink example uses GPIO1 - swap for your board's LED pin if different.
Board: Lolin S2 Mini
USB CDC On Boot: Enabled
Flash Size: 4MB · DIO
Upload Speed: 921600
// blink
pinMode(1, OUTPUT);
digitalWrite(1, LOW); // on (often inverted)[env:lolin_s2_mini]
platform = espressif32
board = esp32-s2-saola-1
framework = arduino
monitor_speed = 115200
upload_speed = 921600esp32:
board: esp32-s2-saola-1
variant: lolin_s2_mini
framework:
type: esp-idf
# blink - GPIO1
output:
- platform: gpio
pin: 1
id: led_out
light:
- platform: binary
name: "LED"
output: led_outesptool.py --chip esp32s2 --port /dev/ttyACM0 \
write_flash 0x0 firmware.binBuild details: sketch space 1310720 B · data 327680 B · DIO
Specifications
ESP32-S2 · 34.3 × 25.4 mmCompute
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 · 1 · 4
PWM
8 channels
Power
USB
USB-C
Serial
Native (CDC)
Boot address
0x1000
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
Similar boards
