ESP32-S3 4.2inch RLCD Development Board
ESP32-S3 4.2inch RLCD Development Board
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Overview

Features
The ESP32-S3-RLCD-4.2 is a RLCD AIoT development board based on ESP32-S3, supporting Wi-Fi and BLE dual-mode communication. Onboard 4.2inch RLCD with low power consumption, e-paper-like display experience, and faster refresh response. Integrated with audio codec circuit, dual microphones, speaker, SHTC3 high-precision temperature and humidity sensor, TF card slot, RTC header, and Lithium Batt charging and discharging management circuit, etc. Reserved USB, UART, I2C, and multiple GPIO interfaces for easy expansion. Supports AI Voice Interaction, temperature and humidity monitoring, and IoT control, making it suitable for DIY desktop smart ornaments, electronic calendars, AI smart devices, and other applications. Also ideal for product prototyping.
- Adopts high-performance Xtensa 32-bit LX7 dual-core processor, up to 240MHz main frequency
- Supports 2.4GHz Wi-Fi and Bluetooth 5 (LE), with onboard antenna
- Built-in 512KB Static RAM, 384KB ROM, with integrated 16MB Flash and 8MB PSRAM
- Onboard 4.2inch RLCD, 300 × 400 resolution, features reflective imaging and no backlight required
- Equipped with a dual-microphone array, enabling audio algorithms such as noise reduction and echo cancellation, suitable for accurate voice recognition and near-field / far-field voice wake-up applications
- Onboard PCF85063 RTC chip and SHTC3 temperature & humidity sensor for accurate RTC management and environmental monitoring
- Onboard 18650 Lithium Batt holder and RTC backup Batt header. The RTC backup Batt header supports a rechargeable RTC Batt and dual modes of main Batt power supply and RTC independent power supply
- Onboard TF card slot for external storage of images or files
- Onboard programmable KEY and BOOT side buttons for customized function development
- Reserved 2 × 8PIN 2.54mm pitch female header for convenient external expansion
Specifications
| Display panel | RLCD | Display size | 4.2inch |
|---|---|---|---|
| Resolution | 300 × 400 | Grey scale | 2 |
| Interface | SPI | Display Mode | reflective |
| Driver IC | ST7305 | Display color | black, white |
Onboard audio codec chip
Supports high-quality audio processing, providing clear and high-quality audio input and output
Supports AI Voice Interaction
Allows access to online large model platforms such as DeepSeek, Doubao, etc
Reflective Liquid Crystal Display
The Reflective Liquid Crystal Display (RLCD) is a specialized type of LCD that efficiently utilizes ambient light (such as natural sunlight or indoor illumination) instead of a backlight, achieving both energy efficiency and environmental friendliness. Thanks to its reflective design, RLCDs perform exceptionally well in bright environments, where conventional LCDs may suffer from glare and reduced visibility. By effectively reflecting external light, the RLCD can provide a clear, high-quality visual experience.
Application Scenarios
Ideal for DIY desktop smart ornaments, electronic calendars, AI smart devices,
outdoor displays and more


Supports ESP-IDF, Arduino IDE
Comprehensive SDK, dev resources, and tutorials to help you easily get started
What's On Board
-
ESP32-S3-WROOM-1-N16R8
The SoC with Wi-Fi and Bluetooth, 240MHz main frequency, integrated with 16MB Flash and 8MB PSRAM -
ES7210
ADC chip for echo cancellation circuit -
ES8311
Low-power audio codec chip -
BOOT button
Press it when powering on to enter download mode -
PWR button
Long press to power off, short press to power on -
KEY button
Customizable for other functions -
SHTC3 temperature and humidity sensor
Provides ambient temperature and humidity measurement, enabling environmental monitoring function -
PCF85063
RTC chip with timekeeping function -
MX1.25 2PIN speaker header
Audio output signal, for connecting external speaker -
RTC independent power supply header
Supports PH1.0 rechargeable RTC Batt only - 2 × 8PIN 2.54mm pitch female header
- 18650 Lithium Batt holder
-
Dual-microphone array design
Dual-microphone array, paired with ES7210 to achieve echo cancellation -
CHG charging indicator
Off when fully charged -
WRN warning indicator
Stays on when Batt is reverse-connected -
Type-C port
For program burning and log printing -
TF card slot
Supports FAT32 TF card for data expansion
Pin Definition
Outline Dimensions
Package Contents
Acrylic stand (2PCS) x1
8Ω 2W MX1.25 2PIN speaker x1
Screwdriver x1
