Waveshare ESP32-S3-RLCD-4.2 is a 4.2-inch Reflective LCD (RLCD) development board built around ESP32-S3 wireless SoC for DIY projects, rapid prototyping, and smart display devices that need a paperlike experience with a higher refresh rate compared to e-paper displays.
The ESP32-S3 provides 2.4 GHz Wi-Fi and Bluetooth 5 LE connectivity, and the board also includes a dual microphone array with ES7210 ADC and ES8311 audio codec, as well as an onboard speaker for AI voice interaction. Other features include an SHTC3 temperature and humidity sensor, a PCF85063 RTC, a microSD card slot for storage, along with multiple GPIO, UART, and I²C expansion headers. Power, programming, and battery charging are done through the USB Type-C port connected to an optional 18650 battery. Applications include electronic calendars, desktop displays, voice-based devices, environmental monitoring, and low-power indoor or outdoor display systems.
ESP32-S3-RLCD-4.2 specifications
- Core module – Espressif Systems ESP32-S3-WROOM-1-N16R8
- SoC – ESP32-S3
- CPU – Dual-core LX7 processor with up to 240MHz
- Memory – 512KB SRAM, 8MB PSRAM
- Storage – 384KB ROM
- Wireless – WiFi 4 802.11b/g/n and Bluetooth 5.0 LE
- Storage – 16MB flash
- PCB antenna
- SoC – ESP32-S3
- Storage – MicroSD card slot
- Display – 4.2-inch 400 x 300 pixels black and white RLCD; ST7305 driver; No backlight (ambient light reflective display)
- USB – USB Type-C port for power programming and charging
- Audio
- ES8311 low-power audio codec
- ES7210 ADC for microphone input with dual-microphone array
- Onboard speaker + external speaker header
- Supports noise reduction and echo cancellation
- Sensors – SHTC3 temperature & humidity sensor
- Expansion – 2x 8-pin 2.54 mm female headers with GPIO, UART, I²C, ADC, USB signals
- Misc
- Power, Boot, and User buttons
- PCF85063 RTC chip with RTC independent power supply header
- MX1.25 2PIN speaker header
- Charging and warning indicator LED
- Power
- 5V from USB Type-C for power, programming, and charging
- Onboard 18650 lithium battery holder (optional battery version)
- Battery charging and protection circuitry
- Charging and warning LEDs
- Dimensions
- Overall size – 92.5 × 70.1 x 13.5 mm (W × H x T, front and side view)
- Tilt angle – 60° (Side view)
- Mounting – 4 × M2.5 holes
In terms of software, the company mentions it supports the ESP-IDF framework and the Arduino IDE. Waveshare would generally provide SDK, example projects, and documentation for the Reflective LCD driver, audio input/output, Wi-Fi and BLE connectivity, RTC, sensors, and SD card access on their website, but at the time of writing, the wiki for their latest ESP32-S3 devkit is empty.
A Reflective LCD (RLCD) is a type of LCD that uses ambient light instead of a backlight to display images, found in devices such as the Eazeye’s 24-inch 60 Hz 1920×1080 RLCD monitor. We also reviewed a 15.6-inch portable Transflective LCD (TLCD), but the technology is different. The display reflects incoming light from its surface, which keeps power consumption very low and makes it easy to read in bright environments, including sunlight. Since there is no backlight, RLCDs consume less power than normal LCDs (but it’s more than an e-paper display) and generate less heat, but they work best when enough external light is available.
The ESP32-S3-RLCD-4.2/EN is available on Aliexpress for $30.99/$33.99 on Amazon for $35.99/$37.99, and on the Waveshare store for $26.99/$24.99 with or without a battery. The development board ships with an optional 18650 rechargeable Lithium battery, an 8Ω 2W speaker, and a screwdriver.
Debashis Das is a technical content writer and embedded engineer with over five years of experience in the industry. With expertise in Embedded C, PCB Design, and SEO optimization, he effectively blends difficult technical topics with clear communication
Support CNX Software! Donate via cryptocurrencies, become a Patron on Patreon, or purchase goods on Amazon or Aliexpress. We also use affiliate links in articles to earn commissions if you make a purchase after clicking on those links.
