ZecTrix Note 4 Puts an AI Voice Notepad on E-Paper

The ZecTrix Note 4 is the kind of board-level product I like taking apart on paper before it ever reaches a bench: a 97 x 97 x 8.75 mm square of E-Ink, an Espressif ESP32-S3, a microphone, a speaker, and a battery large enough that you stop thinking about charging it. ZecTrix Lab is selling the premium model at $54.99 on Tindie, which puts a voice-driven E-Ink smart display in the same price bracket as a bare development kit.

• 4.2-inch E-Ink panel at 400x300, with a four-color BWRY variant (Note 4C) selling for around $30
• ESP32-S3 dual-core LX7 at 240 MHz, 512 KB SRAM plus 8 MB PSRAM, and 16 MB of flash
• Wi-Fi 4 on 2.4 GHz, Bluetooth LE 5.0, and NFC, with a 2,000+ mAh battery charged over USB-C
• Stock firmware ships a Qwen3.5 voice assistant; custom LLM APIs are not supported yet

What Hardware Is Inside the ZecTrix Note 4?

The ESP32-S3 is the sensible choice here, and the memory budget is what makes it interesting. 8 MB of PSRAM is a lot of headroom for a device whose main job is compositing a 400x300 monochrome framebuffer, which means there is room left over for audio buffers and network state. That combination is why the ESP32-S3 keeps showing up in ambitious builds — we recently covered a 28.9M-parameter LLM running on an ESP32-S3 at nine tokens per second on the same silicon family.

The I/O list is short and deliberate. A dedicated voice button sits under your thumb, side buttons handle navigation, and NFC is there for tap-to-configure pairing. E-Ink means the panel draws power only when the image changes, so the 2,000 mAh cell is oversized on purpose — this is a device meant to sit on a shelf for weeks.

How Does the Voice Assistant Work?

Out of the box, the Note 4 routes captured audio to a Qwen3.5 assistant, and the premium $54.99 tier bundles that AI voice service. You speak, it transcribes, and the result lands on the E-Ink page as a note or reminder. The stock firmware does not currently accept custom model endpoints or third-party LLM APIs, which is the one specification that will matter most to the self-hosted crowd.

That gap is already being filled from the outside. Community firmware projects have repurposed the hardware as a coding-assistant display, a transit-arrival board, and a general dashboard. This is the familiar pattern for open E-Ink hardware — the same one that played out with the reTerminal Sticky ePaper and its four open firmwares.

Who Is This For?

If you want a low-power always-on surface for reminders, weather, a clock, or a rotating image frame, the monochrome Note 4 at $54.99 is a complete product. If you would rather treat it as a chassis and write your own firmware against the ESP32-S3, the $30 four-color Note 4C is the better value, and the BWRY panel gives you red and yellow accents to work with.

The practical caveat is the panel refresh rate. E-Ink is not a live display, so anything requiring sub-second updates belongs on different hardware. For everything else — a desk companion that runs for weeks and answers when you press the button — this is one of the more complete ESP32-S3 packages to arrive this year. More builds like it land regularly in our mini computer coverage.

Sources: CNX Software — August 5, 2026.