LilyGo T4-S3 Development Board
Code name: LILYGO_T4_S3
LilyGo T4-S3 development board is based on esp32s3 microcontroller and uses xtensa architecture. This board has a maximum CPU frequency of 240 MHz and a flash size of 16MB.
About LilyGo T4-S3
🚀 The LilyGo T4-S3 is an ESP32-S3-based development board designed for high-performance IoT applications. Featuring a large 4.2-inch e-paper 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.
Technical Specifications
🖥️ Display
🛰️ Connectivity
🧠 Microcontroller
✨ Features
- 48 digital IO pins
- 46 external interrupt pins
- 20 analog input pins
- 27 PWM pins
LilyGo T4-S3 Pinout
✅ Safe Pins to Use
For general GPIO usage, these are the safest and most flexible choices:
Why Are These Pins Safe?
- Not involved in bootstrapping → No impact on device boot mode or system startup
- Not linked to flash memory or PSRAM → Won't interfere with storage or memory access
- Not dedicated to USB or JTAG → Free for general use without affecting debugging
- No special hardware connections → Freely assignable without internal conflicts
⚠️ Pins to Avoid or Use with Caution
Some pins are reserved for critical functions like bootstrapping, JTAG debugging, USB communication, and flash memory operations. Misusing these pins may lead to boot failures, programming issues, USB conflicts, or disruptions in flash storage.
Critical Pin Categories:
- 🛠️ Strapping Pins: Control boot behavior and flash voltage selection
- 🔗 JTAG Debugging Pins: Required for low-level debugging
- 🔌 USB Communication Pins: Used for USB Serial/JTAG communication
- ⚡ Flash Memory & SPI Pins: Connected to SPI flash memory and PSRAM
- 📡 UART Serial Communication Pins: Used for debugging and firmware uploads
| PIN | Label | Reason | Function |
|---|---|---|---|
| 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 |
| IO19 | USB_D- | By default connected to the on-chip USB Serial/JTAG controller. Using it as general GPIO without reconfiguring IO MUX will interfere with USB functionality. | 🔌 USB |
LilyGo T4-S3 Pin Mappings
This development board provides 48 digital IO pins, out of which 46 can be used as external interrupt pins , 20 as analog input pins and 27 pins have Pulse-Width Modulation (PWM) .
| Pin | Function | ESP Pin | Input/Output | Description |
|---|---|---|---|---|
| 1 | 3V3 | 3.3V | POWER OUTPUT | 3.3V power output |
| 2 | GND | GND | POWER GROUND | Ground connection |
| 3 | 5V | 5V | POWER INPUT | 5V power input |
| 4 | IO1 | GPIO1 | BIDIRECTIONAL | GPIO, ADC, I2C |
| 5 | IO2 | GPIO2 | BIDIRECTIONAL | GPIO, ADC |
| 6 | IO3 | GPIO3 | BIDIRECTIONAL | GPIO, ADC |
| 7 | IO16 | SPI_CS | BIDIRECTIONAL | GPIO, SPI Chip Select |
| 8 | IO17 | SPI_D | BIDIRECTIONAL | GPIO, SPI Data |
| 9 | IO18 | SPI_CLK | BIDIRECTIONAL | GPIO, SPI Clock |
| 10 | IO19 | SPI_Q | BIDIRECTIONAL | GPIO, SPI Q |
| 11 | IO21 | EPD_DC | OUTPUT | GPIO, E-Paper Data/Command |
| 12 | IO22 | EPD_RST | OUTPUT | GPIO, E-Paper Reset |
| 13 | IO23 | EPD_BUSY | INPUT | GPIO, E-Paper Busy Signal |
Default Tools
| Bootloader tool | esptool_py |
| Uploader tool | esptool_py |
| Network uploader tool | esp_ota |
| Bootloader address | 0x0 |
| Flash mode | dio |
| Boot mode | qio |
| PSRAM type | opi |
| Maximum upload size | 3072 Kb (3145728 B) |
| Maximum data size | 320 Kb (327680 B) |
The LilyGo T4-S3 development board by default uses esptool_py uploader tool, esp_ota network uploader tool for Over-the-air (OTA) uploads and esptool_py bootloader tool. The bootloader starts at address "0x0". Flash mode and boot mode for LilyGo T4-S3 development board by default is dio and qio respectively. The board uses opi PSRAM type. When using Arduino IDE, the maximum sketch upload size is 3072 Kb (3145728 B) and maximum data size for variables is 320 Kb (327680 B).
