LilyGo T4-S3
A versatile ESP32-S3 board by LilyGo, suitable for a wide range of IoT and embedded projects.
LilyGo T4-S3 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 | safe | - | 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 | uart | uart | UART0 TX - 2x15 header and UART Qwiic connector |
| 18 | 44 | RXDIO44 | uart | 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
7 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
9 pins · 8 things to knowIO3 Bootstrapping pin (controls JTAG signal source) Strapping
Sampled at reset to select JTAG interface (USB Serial/JTAG controller vs. external pins). Improper use can disable external JTAG or alter debug interface.
IO39 JTAG test clock (MTCK); IO MUX alternates CLK_OUT3 and SUBSPICS1 (chip select on the alternative SUBSPI memory bus, unused on standard modules) JTAG
Default JTAG TCK - keep it free if you debug over JTAG. It is not a flash or PSRAM line on standard modules: those sit on GPIO26-37.
IO40 JTAG test data out pin (MTDO) JTAG
Default JTAG TDO output for debugging. Using it as GPIO will interfere with JTAG debugging functionality.
IO41 JTAG test data in pin (MTDI) JTAG
Default JTAG TDI input for debugging. Should be reserved for JTAG or left unused if JTAG is to remain available.
IO42 JTAG test mode select pin (MTMS) JTAG
Default JTAG TMS signal for debugging. Using this pin for other purposes will disable the JTAG interface (unless JTAG is rerouted to USB).
TXDGPIO43 UART0 transmit pin (U0TXD), default serial console TX UART
Used for bootloader output and UART console logs. If repurposed, you will lose the default serial output (and programming via UART0).
RXDGPIO44 UART0 receive pin (U0RXD), default serial console RX UART
Used for bootloader input (download mode via serial). If repurposed, you cannot use the default UART0 download mode for programming the chip.
IO47IO48 Octal SPI differential clock legs (SPICLK_P/N_DIFF), used only by the 1.8 V octal flash/PSRAM variants Other
Only the 1.8 V octal parts (ESP32-S3R8V, ESP32-S3R16V) run the differential memory clock here, and on those the pin works at 1.8 V instead of 3.3 V. On the common 3.3 V modules it is a normal GPIO - several devkits drive their RGB LED from GPIO48.
- IO47Octal SPI differential clock positive leg (SPICLK_P_DIFF), used only by the 1.8 V octal flash/PSRAM variants
- IO48Octal SPI differential clock negative leg (SPICLK_N_DIFF), used only by the 1.8 V octal flash/PSRAM variants
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 3 more are free of any such role - the safest first picks. 9 of the exposed pins carry boot-time or system duties on the ESP32-S3 (IO3, IO39, IO40 and 6 more).
Getting started
flash your first firmware in ~2 minutesBoard: ESP32S3 Dev Module USB CDC On Boot: Enabled Flash Size: 16MB (128Mb) Flash Mode: DIO PSRAM: OPI PSRAM Partition Scheme: 16M Flash (3MB APP/9.9MB FATFS) Upload Speed: 921600
// 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);
}[env:lilygo_t4_s3]
platform = espressif32
board = esp32-s3-devkitc-1
framework = arduino
monitor_speed = 115200
upload_speed = 921600
board_build.arduino.memory_type = qio_opi
build_flags = -DBOARD_HAS_PSRAMesp32-s3-devkitc-1 - or type it after board =.esp32:
board: esp32-s3-devkitc-1
variant: esp32s3
framework:
type: esp-idf
psram:
mode: octal
speed: 80MHz
# blink - GPIO1
output:
- platform: gpio
pin: 1
id: led_out
light:
- platform: binary
name: "LED"
output: led_outesp32-s3-devkitc-1 (same ids as PlatformIO).esptool.py --chip esp32s3 --port /dev/ttyACM0 \
--baud 921600 write_flash 0x0 firmware.bin--port = your /dev/tty* (macOS/Linux) or COMx (Windows).Specifications
ESP32-S3 · 56 × 44 mm · vs other ESP32 chips →Dimensions
About 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 ~$29 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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