LilyGo T4-S3
A versatile ESP32-S3 board by LilyGo, suitable for a wide range of IoT and embedded projects.
Pinout
20 pins
| Pin | GPIO | Labels | Status | Capabilities | Notes |
|---|---|---|---|---|---|
| 1 | - | 3V33.3V | power | - | 3.3V power - 2x15 header and both Qwiic connectors |
| 2 | - | VBUS5V | power | - | 5V from USB-C (VBUS) - 2x15 header |
| 3 | - | BATVBAT | power | - | Battery voltage (VBAT) - 2x15 header |
| 4 | - | GND | ground | - | Ground - 2x15 header and both Qwiic connectors |
| 5 | 1 | IO1SD_CS | safe | adc · touch · spi | microSD chip select - 2x15 header (shared with microSD slot) |
| 6 | 2 | IO2SD_MOSI | safe | adc · touch · spi | microSD MOSI - 2x15 header (shared with microSD slot) |
| 7 | 3 | IO3SD_SCK | strapping | adc · touch · spi | microSD SCK - 2x15 header (shared with microSD slot) |
| 8 | 4 | IO4SD_MISO | safe | adc · touch · spi | microSD MISO - 2x15 header (shared with microSD slot) |
| 9 | 6 | SDAIO6 | safe | adc · touch · i2c | I2C SDA - 2x15 header and Qwiic (shared with CST226SE touch and SY6970 PMU) |
| 10 | 7 | SCLIO7 | safe | adc · touch · i2c | I2C SCL - 2x15 header and Qwiic (shared with CST226SE touch and SY6970 PMU) |
| 11 | 21 | IO21 | safe | - | Free GPIO - 2x15 header |
| 12 | 38 | IO38 | strapping | - | Free GPIO - 2x15 header |
| 13 | 39 | IO39 | strapping | - | Free GPIO - 2x15 header |
| 14 | 40 | IO40 | strapping | - | Free GPIO - 2x15 header |
| 15 | 41 | IO41 | strapping | - | Free GPIO - 2x15 header |
| 16 | 42 | IO42 | strapping | - | Free GPIO - 2x15 header |
| 17 | 43 | TXDIO43 | strapping | uart | UART0 TX - 2x15 header and UART Qwiic connector |
| 18 | 44 | RXDIO44 | strapping | uart | UART0 RX - 2x15 header and UART Qwiic connector |
| 19 | 47 | IO47 | strapping | - | Free GPIO - 2x15 header |
| 20 | 48 | IO48 | strapping | - | Free GPIO - 2x15 header |
Start with these
6 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
sampled at boot or shared with debug/serial| Pin | Label | What to know | Role |
|---|---|---|---|
| IO3 | 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 |
| IO39 | MTCK (GPIO39) | Default JTAG debugging TCK pin. If JTAG is needed, this pin must be free; it may also be used internally for PSRAM chip select on certain modules, so avoid repurposing it. | Other |
| IO40 | MTDO (GPIO40) | Default JTAG TDO output for debugging. Using it as GPIO will interfere with JTAG debugging functionality. | Other |
| IO41 | MTDI (GPIO41) | Default JTAG TDI input for debugging. Should be reserved for JTAG or left unused if JTAG is to remain available. | Other |
| IO42 | 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 |
| TXD | U0TXD (GPIO43) | Used for bootloader output and UART console logs. If repurposed, you will lose the default serial output (and programming via UART0). | Other |
| RXD | 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 |
|---|---|---|---|
| IO38 | 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 |
| IO47 | SPICLK_P | Used only on variants with Octal SPI interface (e.g. ESP32-S3R16V) as part of the differential clock pair. On such chips it operates at 1.8 V and is reserved for the high-speed octal SPI clock, not for general GPIO use. | Flash |
| IO48 | SPICLK_N | Used only on variants with Octal SPI interface, as the negative leg of the differential clock&. On such chips it operates at 1.8 V; it should be avoided for GPIO to prevent conflicts with the octal flash/PSRAM clock. | Flash |
Pinout notes The LilyGo T4-S3 breaks out 20 pins in total: 16 GPIO for your project, with 3V3 , VBUS , BAT and GND handling power. For peripherals, I²C is mapped to SDA on…
The LilyGo T4-S3 breaks out 20 pins in total: 16 GPIO for your project, with 3V3, VBUS, BAT and GND handling power.
For peripherals, I²C is mapped to SDA on GPIO6 and SCL on GPIO7.
On the analog side there are 6 ADC-capable pins for sensors and battery monitoring and 6 capacitive-touch inputs.
If you want zero surprises, IO1, IO2, IO4, SDA and 2 more are free of any such role - the safest first picks. 7 of the exposed pins carry boot-time or system duties on the ESP32-S3 (IO3, IO39, IO40 and 4 more).
Getting started
flash your first firmware in ~2 minutesBoard: Lilygo T4 S3
USB CDC On Boot: Enabled
Flash Size: 16MB · DIO
Upload Speed: 921600
// blink
pinMode(1, OUTPUT);
digitalWrite(1, LOW); // on (often inverted)[env:lilygo_t4_s3]
platform = espressif32
board = esp32-s3-devkitc-1
framework = arduino
monitor_speed = 115200
upload_speed = 921600esp32:
board: esp32-s3-devkitc-1
variant: lilygo_t4_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.binSpecifications
ESP32-S3 · 56 × 44 mmAbout this board
At its core is the ESP32-S3 - a dual-core Xtensa with vector extensions suited to AI workloads.
Expect to pay about $58.99 - above the ~$30 typical for ESP32-S3 boards.
Only 16 GPIO are left for your own hardware - the display and onboard peripherals claim the rest.
Onboard you'll find 8MB (OPI) PSRAM, an AMOLED 2.41" 450x600 display with touch, battery charging (SY6970) via JST 1.25mm and Reset/Boot buttons.
It flashes over native USB - no serial-converter driver needed, which isn't a given among ESP32-S3 boards.
The LilyGo T4-S3 is an ESP32-S3-based development board designed for high-performance IoT applications. Featuring a large 2.41-inch AMOLED display and low-power consumption, it is ideal for smart display projects.
With WiFi 802.11 b/g/n and Bluetooth 5 (LE), it supports seamless wireless communication, making it perfect for remote monitoring and embedded systems.
The T4-S3 comes with 8MB PSRAM and 16MB Flash, providing ample memory for complex applications.
Where to buy
prices are typical street pricesResources
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