ESP32-S3 4.2inch RLCD Development Board

The Waveshare ESP32-S3-RLCD-4.2 is a feature-packed, low-power AIoT development board centered around a 4.2-inch Reflective Liquid Crystal Display (RLCD), offering an e-paper-like reading experience with significantly faster refresh rates. This battery-included version (bundled with 18650 Lithium battery) integrates ESP32-S3 wireless connectivity, dual microphones for AI voice interaction, environmental sensors, and extensive expansion options, making it perfect for DIY smart devices, electronic calendars, outdoor displays, and rapid product prototyping in IoT applications.

Key Specifications

• Display Panel: 4.2-inch RLCD with 300×400 resolution, 2 grayscale levels, SPI interface, reflective mode (no backlight needed), driven by ST7305 IC for black-and-white visuals that excel in ambient light.

• Processor & Memory: ESP32-S3-WROOM-1-N16R8 SoC with high-performance Xtensa 32-bit LX7 dual-core at up to 240MHz, 512KB SRAM, 384KB ROM, integrated 16MB Flash, and 8MB PSRAM.

• Wireless: 2.4GHz Wi-Fi and Bluetooth 5 (LE) with onboard antenna for seamless connectivity.

• Sensors: SHTC3 high-precision temperature and humidity sensor; PCF85063 RTC chip for accurate timekeeping and environmental monitoring.

• Audio: Dual-microphone array with ES7210 ADC for noise reduction/echo cancellation, ES8311 low-power codec for high-quality input/output, and MX1.25 2PIN speaker header.

• Power Management: Onboard 18650 Lithium battery holder (included), RTC backup battery header (supports PH1.0 rechargeable RTC battery), dual power modes (main battery or RTC-independent), CHG/WRN indicators.

Connectivity and Controls

Designed for easy expansion and development:

• Type-C port for programming, debugging, and log printing.

• TF card slot (FAT32 support) for storing images, files, or data.

• 2× 8PIN 2.54mm pitch female headers exposing USB, UART, I2C, multiple GPIOs.

• Programmable buttons: BOOT (for download mode), PWR (power on/off), KEY (user-customizable).

• Additional headers: RTC independent power, speaker output.

Standout Features

RLCD technology reflects ambient light for ultra-low power consumption, superior sunlight readability, and eco-friendliness—ideal for battery-powered outdoor or portable uses. Supports AI voice interaction with platforms like DeepSeek or Doubao, enabling far-field wake-up and voice recognition. Comprehensive audio processing delivers clear sound for smart assistants or alerts. Passive elements like the battery holder and RTC ensure long runtime without frequent recharges. Development-friendly with ESP-IDF and Arduino IDE support, plus SDKs, tutorials, and resources for quick prototyping of desktop ornaments, AI gadgets, or IoT controllers.

Application Scenarios

Perfect for energy-efficient projects such as:

• DIY electronic calendars or smart clocks with weather/environment display.

• Voice-activated AI devices for home automation.

• Outdoor signage or wearables leveraging reflective display.

• Prototyping IoT sensors with temp/humidity logging and wireless control.

What's On Board Highlights

• ESP32-S3 Core: Powers all wireless, processing, and peripheral functions.

• Audio Subsystem: ES7210 + ES8311 + dual mics for advanced voice apps.

• Sensors & RTC: SHTC3 + PCF85063 for precise monitoring and scheduling.

• Expansion-Ready: Headers, TF slot, and battery integration for standalone operation.

• Indicators: CHG (off when full), WRN (alerts reverse polarity).

Package Contents 

Weight: 0.187 kg

1. ESP32-S3-RLCD-4.2 host x1
2. Acrylic stand (2PCS) x1
3. 18650 rechargeable Lithium Batt x1
4. 8Ω 2W MX1.25 2PIN speaker x1
5. Screwdriver x1