4.2-inch ESP32-S3-based E Ink display works as a sticky note, taking voice input from its user https://cnx-software.com/2026/08/05/zectrix-note-4-a-4-2-inch-esp32-s3-wireless-e-paper-display-for-voice-tasks/…

ZecTrix Lab’s Note 4 features 2.4GHz Wi-Fi and Bluetooth 5.0 connectivity, a microphone, a speaker, NFC, physical buttons, a USB Type-C port, a 2,000mAh rechargeable battery, and GPIO expansion for custom hardware projects.

It’s designed for display reminders, notes, clocks, weather, images, and custom templates. Several open-source firmware projects are also supported.

ZecTrix Note 4 – A 4.2-inch ESP32-S3 wireless e-paper display for voice tasks - CNX Software

Source: https://www.cnx-software.com/2026/08/05/zectrix-note-4-a-4-2-inch-esp32-s3-wireless-e-paper-display-for-voice-tasks/ Designed by ZecTrix Lab in China, theNote****4is an ESP32-S3-based AI smart note with a 4.2-inch e-paper display and built-in voice input. The device is designed to display reminders, notes, clocks, weather, images, and custom templates, while theNote 4Cvariant replaces the monochrome display with a four-color e-paper panel.

The device features 2.4GHz Wi-Fi and Bluetooth 5.0 connectivity, a microphone, a speaker, NFC, physical buttons, a USB Type-C port, a 2,000mAh rechargeable battery, and GPIO expansion for custom hardware projects.

ZecTrix Note 4 / Note 4C specifications:

• SoC –Espressif Systems ESP32-S3- CPU – Dual-core Tensilica LX7 up to 240 MHz with vector extension for AI/ML workloads - RAM – 512KB SRAM; 8MB PSRAM - Wireless – WiFi 4 and Bluetooth LE 5
• Storage – 16MB flash
• Display- Note 4– 4.2-inch monochrome E-Ink display, 400 × 300 resolution; supports partial refresh - Note 4C– 4.2-inch four-color (BWRY) E-Ink display, 400 × 300 resolution
• Audio – Built-in microphone and speaker for voice input and alerts
• USB – USB Type-C port for charging and data
• Expansion – Header with 3.3V, GND, TX, RX, and 2x GPIO pins
• Misc- Voice/confirm button - Side function buttons - NFC, status indicator - Magnetic backplate - Built-in Real-Time Clock (PCF8563)
• Power- 5V via USB Type-C port - Built-in 2,000+ mAh rechargeable battery
• Dimensions – 97 × 97 × 8.75 mm
• Enclosure- Minimal Premium Edition – Injection-molded “calm technology” design - Everyday Edition – Standard hardware for DIYers - Color Edition – ZecTrix provides open-source 3D model files for enthusiasts to print themselves
• Mounting – Magnetic backplate

The official firmware uses a cloud-based Qwen3.5 AI voice assistant, but it currently does not support custom AI models or LLM APIs. If you want to use your own AI services, you will need to install one of the available community firmware projects. The official firmware currently supports Chinese only, with an English preview planned before September 2026. The company alsoprovides documentationand actively supports several community-developed open-source firmware projects. These allow developers to repurpose the device as an information dashboard, AI voice assistant, coding remote, transit display, TRMNL client, and other ESP32-S3-based applications.

Speaking of the open-source projects, some of those projects includevibecoding-voiceandvibecoding-plus, which let the Note 4 be used as a voice input device for AI coding tools such as OpenAI Codex and Claude Code. Other community firmware includesSlate, an open-source firmware framework with a web management interface and backend services,xiaozhi-zectrix, which ports the XiaoZhi AI assistant firmware to the device with dual-boot support, andTransitInk OSfirmware for displaying real-time public transit information on the e-paper display.

ZecTrix Note 4CZecTrix Note 4C InternalsLooking at the complete features and specifications, this device reminds me ofSeeed Studio’s reTerminal Sticky, as both are ESP32-S3-based magnetic e-paper notes designed for AI voice-to-text household reminders. The reTerminal Sticky costs $49.99 and comes with a 3.97-inch touchscreen, while the ZecTrix Note 4 has physical buttons and a slightly larger 4.2-inch e-paper display. We have also written about other ESP32-based e-paper devices, including the open-sourceTRMNL 7.5-inch wireless E-Ink display, whose firmware is ported to the ZecTrix Note 4. We’ve also covered the ESP32-powered Inkplate series, including theInkplate 6, Seeed Studio’sreTerminal E1001/E1002 e-paper displays, and theMerlot 4.2-inch e-paper display. All of these typically lack audio support found in the Note 4/4C and reTerminal Sticky.

ZecTrix Lab is selling only the premium edition of theNote 4 on Tindie for $54.99, with worldwide shipping starting at 18\.00\. Interestingly, the Note 4C is not available on Tindie, but you’ll find it on[Taobao for ¥999 \(~147.92)](https://item.taobao.com/item.htm?ft=t&id=1066441008525).

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

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