Designed by ZecTrix Lab in China, the Note 4 is 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 the Note 4C variant 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 also provides documentation and 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 include vibecoding-voice and vibecoding-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 includes Slate, 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, and TransitInk OS firmware for displaying real-time public transit information on the e-paper display.
Looking at the complete features and specifications, this device reminds me of Seeed 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-source TRMNL 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 the Inkplate 6, Seeed Studio’s reTerminal E1001/E1002 e-paper displays, and the Merlot 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 the Note 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 the company’s website for 199 CNY (about $30), somehow cheaper than the monochrome Note 4 going for 259 CNY. Grok tells us it’s because the Note 4 comes with “lifetime AI voice task/reminder service”, but the color variant doesn’t.
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.
