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LOLIN S3
A development board by Wemos based on the ESP32-S3-WROOM-1, featuring dual USB-C ports and compatibility with MicroPython and Arduino.
65.3 × 25.4 mm
ESP32-S3
MCU
240MHz
clock
16MB
flash
512KB
SRAM
23· 18 ADC
GPIO
BLE 5.0+ WiFi
radio
Pinout
23 pins · 2.54 mm pitch
| Pin | GPIO | Labels | Status | Capabilities | Notes |
|---|---|---|---|---|---|
| 1 | 1 | A0T1PWM | safe | adc · touch | |
| 2 | 2 | A1T2PWM | safe | adc · touch | |
| 3 | 3 | A2T3PWM | strapping | adc · touch | |
| 4 | 4 | A3T4PWM | safe | adc · touch | |
| 5 | 5 | A4T5PWM | safe | adc · touch | |
| 6 | 6 | A5T6PWM | safe | adc · touch | |
| 7 | 7 | A6T7PWM | safe | adc · touch | |
| 8 | 8 | A7T8PWM | safe | adc · touch | |
| 9 | 9 | A8T9PWM | strapping | adc · touch | |
| 10 | 10 | SSA9T10PWM | strapping | adc · touch · spi | |
| 11 | 11 | MOSIA10T11PWM | strapping | adc · touch · spi | |
| 12 | 12 | SCKA11T12PWM | strapping | adc · touch · spi | |
| 13 | 13 | MISOA12T13PWM | strapping | adc · touch · spi | |
| 14 | 14 | A13T14PWM | strapping | adc · touch | |
| 15 | 15 | A14PWM | safe | adc | |
| 16 | 16 | A15PWM | safe | adc | |
| 17 | 17 | A16PWM | safe | adc | |
| 18 | 18 | A17PWM | safe | adc | |
| 19 | 38 | LED_BUILTINPWM | strapping | - | |
| 20 | 41 | SCLPWM | strapping | i2c | |
| 21 | 42 | SDAPWM | strapping | i2c | |
| 22 | 43 | TXPWM | strapping | uart | |
| 23 | 44 | RXPWM | strapping | uart |
Start with these
11 pins with no boot or system involvementA0T1A1T2A3T4A4T5A5T6A6T7A7T8A14PWMA15PWMA16PWMA17PWM
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 |
|---|---|---|---|
| A2 | 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 | MTDI (GPIO41) | Default JTAG TDI input for debugging. Should be reserved for JTAG or left unused if JTAG is to remain available. | Other |
| SDA | 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 |
|---|---|---|---|
| A8 | FSPIHD | Connected to external flash (data/hold signal) on most modules. Not recommended for use as GPIO, since it must remain dedicated to flash communication. | Flash |
| SS | FSPICS0 | Used to select the external flash chip. It is required for flash access and cannot be repurposed without losing flash connectivity | Flash |
| MOSI | FSPID | Used as a data line for flash (and in-package PSRAM). It should not be used as GPIO when the flash/PSRAM is in use. | Flash |
| SCK | FSPICLK | Drives the flash (and PSRAM) clock. This critical signal must be reserved for memory and not used as general GPIO. | Flash |
| MISO | FSPIQ | Used as a data line for flash/PSRAM transfers. Not available for other uses when flash/PSRAM is connected. | Flash |
| A13 | FSPIWP | Connected to external flash (data/write-protect signal). Not recommended as GPIO because it’s reserved for flash operations. | Flash |
| LED_BUILTIN | 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 |
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 All 23 pins on the LOLIN S3 are usable GPIO, spaced at the standard 2.54 mm pitch. Peripheral wiring is straightforward: I²C is mapped to SDA on GPIO42 and SCL…
All 23 pins on the LOLIN S3 are usable GPIO, spaced at the standard 2.54 mm pitch.
Peripheral wiring is straightforward: I²C is mapped to SDA on GPIO42 and SCL on GPIO41; the SPI bus (MOSI, MISO, SCK, SS) is broken out in full; TX/RX on GPIO43 and GPIO44 cover serial logging and flashing.
Beyond plain digital I/O you get 18 ADC-capable pins for sensors and battery monitoring and 14 capacitive-touch inputs.
5 of the exposed pins carry boot-time or system duties on the ESP32-S3 (A2, SCL, SDA and 2 more) - check the guidance above before wiring anything to them. A0, A1, A3, A4 and 7 more are free of any such role - the safest first picks.
Getting started
flash your first firmware in ~2 minutes1
Connect over USB
Serial chip: CH340X. 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 S3
Flash Size: 16MB · DIO
Upload Speed: 921600
// blink
pinMode(1, OUTPUT);
digitalWrite(1, LOW); // on (often inverted)[env:lolin_s3]
platform = espressif32
board = esp32-s3-devkitc-1
framework = arduino
monitor_speed = 115200
upload_speed = 921600esp32:
board: esp32-s3-devkitc-1
variant: lolin_s3
framework:
type: esp-idf
# blink - GPIO1
output:
- platform: gpio
pin: 1
id: led_out
light:
- platform: binary
name: "LED"
output: led_outesptool.py --chip esp32s3 --port /dev/ttyACM0 \
write_flash 0x0 firmware.binBuild details: sketch space 1310720 B · data 327680 B · DIO
Specifications
ESP32-S3 · 65.3 × 25.4 mmCompute
MCU
ESP32-S3
Clock
240 MHz
SRAM · Flash
512 KB · 16MB · 8MB (OPI) PSRAM
Radio
Wi-Fi
802.11 b/g/n
Bluetooth
5.0 LE
Antenna
PCB
I/O
GPIO · ADC
23 · 18
UART · I²C · SPI
3 · 2 · 4
PWM
8 channels
Power
USB
USB-C (UART) · USB-C (native)
Serial
CH340X
Boot address
0x0
Flashing
Upload · OTA
esptool_py · esp_ota
Flash · Boot mode
DIO · QIO
Sketch · Data
1.25 MB · 320 KB
65.3 × 25.4 mm · pin pitch 2.54 mm
The LOLIN S3 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
Inside sits the ESP32-S3 - a dual-core Xtensa with vector extensions suited to AI workloads.
At $6.90 it's cheaper than most ESP32-S3 boards, which usually run around $30.
Around the module: 8MB (OPI) PSRAM, an addressable RGB LED (GPIO38) and Reset/Boot buttons.
Where to buy
prices are typical street pricesAs an Amazon Associate, ESPboards earns from qualifying purchases.
Resources
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