I just released Rustmix Remote v1.0.0, a small Wear OS app that turns a Samsung Wear OS watch into a BLE page-turning remote for my Waveshare 3.97 e-paper reader.

This is currently validated with the Waveshare ESP32-S3 3.97-inch e-paper device running Rustmix-Wave. It doesn't work with stock firmware or any other firmware.

What it does

Rustmix Remote lets the watch send page-turn commands over BLE GATT to the Rustmix-Wave firmware.

Validated working:

• Wear OS app connects to Rustmix-Wave over BLE
• Previous / Next page controls from the watch
• TXT reader page turning
• EPUB reader page turning
• Swipeable 2-screen watch UI
• Saved BLE device address
• Connect Saved / Scan Fallback
• Disconnect button
• Connection/write status text

The flow is:

Samsung Wear OS watch
    -> BLE GATT
    -> Rustmix-Wave firmware
    -> TXT / EPUB reader page turn

Rustmix Remote watch app

Rustmix Remote v1.0.0 release:

https://github.com/aimindseye/rustmix-watch-remote/releases/tag/v1.0.0

Repo:

https://github.com/aimindseye/rustmix-watch-remote

Which Rustmix-Wave firmware release should you use?

Rustmix-Wave now has two separate firmware release variants for the Waveshare 3.97-inch e-paper device.

Use v1.2.0-wifi for normal daily use

Use this if you want the regular Rustmix-Wave firmware features:

• TXT reader
• EPUB reader
• Indic EPUB support
• Wi-Fi transfer
• weather/network fetch
• NTP/time sync
• voice notes
• calendar
• dictionary
• games
• settings

Wi-Fi release:

https://github.com/aimindseye/rustmix-wave/releases/tag/v1.2.0-wifi

Use v1.2.0-ble for Rustmix Remote watch page turning

Use this if you want the Wear OS watch remote:

• BLE GATT support
• Rustmix Remote page turning
• TXT reader Previous / Next
• EPUB reader Previous / Next

BLE release:

https://github.com/aimindseye/rustmix-wave/releases/tag/v1.2.0-ble

Rustmix-Wave repo:

https://github.com/aimindseye/rustmix-wave

Why two firmware releases?

The Waveshare 3.97-inch e-paper device uses an ESP32-S3. Wi-Fi and Bluetooth LE share the same radio subsystem, and this firmware also has memory/timing-sensitive pieces like:

• e-paper refresh coordination
• SD card access
• TXT/EPUB reader cache workers
• Wi-Fi transfer portal
• weather/network tasks
• BLE GATT command service

For reliable watch-based page turning, the BLE firmware gives BLE ownership of the modem and intentionally disables Wi-Fi/network services.

So:

v1.2.0-wifi = normal firmware with Wi-Fi/network features
v1.2.0-ble  = BLE remote firmware for Wear OS page turning

If you need Wi-Fi transfer, weather, or NTP/time sync, use the Wi-Fi release.
If you want watch-based TXT/EPUB page turning, use the BLE release.

Limitations

This is not a universal Bluetooth HID remote yet.

Current limitations:

• Works with Rustmix-Wave firmware, not stock Waveshare 3.97 e-paper firmware
• BLE build disables Wi-Fi/network features
• Watch app was validated on Samsung Wear OS
• Direct saved BLE MAC fallback is the reliable connection path right now
• You need to flash the correct Rustmix-Wave firmware variant
• This is currently for the Waveshare ESP32-S3 3.97-inch e-paper target

Why I built it

I wanted a simple low-distraction way to turn pages on an e-paper reader from a watch, especially when reading EPUB/TXT hands-free. This also keeps the protocol simple and safe: the BLE callback only parses/enqueues commands, and the firmware main loop handles reader state changes.

Feedback and testing on other Wear OS watches would be appreciated.

Title: Rustmix X4 Firmware v1.1.0 Released — Hindi, Sanskrit, and Gujarati EPUB Support

*** Not Tested on X3 and locked devices***

I have released Rustmix X4 Firmware v1.1.0 for the Xteink X4 e-paper reader.

The main addition in this release is support for reading EPUB books containing:

• Hindi text
• Sanskrit text
• Devanagari script and Vedic marks
• Gujarati text
• Mixed Latin, Devanagari, and Gujarati pages

The new rendering path uses host-side text shaping and page-local font caches, allowing complex Indic scripts to render properly on the resource-constrained X4 device. This includes correct handling of conjuncts, half-forms, matras, and script-specific glyph positioning.

I validated the update on physical hardware with:

• Garud Purana in Hindi and Sanskrit
• Srimad Bhagavat Mahapuran in Hindi
• Valmiki Ramayana in Gujarati

The EPUB pages are rendering properly on the device.

A few implementation details:

• EPUB files continue to use FAT 8.3-safe .EPU filenames.
• Prepared book caches are stored under /FCACHE/<BOOKID> on the SD card.
• Only the active page’s required font assets are loaded into memory.
• Gujarati assets are generated only for books that require them.
• macOS metadata files such as ._* and .DS_Store are cleaned automatically during cache preparation and validation.

The release also preserves the existing reader functionality, including TXT support, EPUB browsing, bookmarks, page navigation, Wi-Fi Transfer, and the standard X4 partition layout.

GitHub repository and release:
https://github.com/aimindseye/rustmix-x4-firmware/releases/tag/v1.1.0

Screenshots of Hindi and Gujarati EPUB rendering are included in the repository under the screenshots/ folder.

Feedback, testing reports, and EPUB samples in additional Indic scripts are welcome.

I created another firmware as learning exercise for my X4 in Rust called - Rustmix.
It is intended as a developer reference and starting point for someone who wants to create firmware in Rust instead of C++.

Rustmix is a reference build inspired by and/or informed by:

• pulp-os: a minimal Xteink X4 Rust firmware lineage.
• Biscuit: dashboard and simple e-reader product UX ideas.
• CrossInk: compact e-ink UI patterns for headers, tabs, rows, and tool screens.
• CrossPoint Reader: open Xteink X3/X4 firmware compatibility goals and partition-layout awareness.
• CrossLuaReader-style SD Lua app experiments: small scripts, constrained host APIs, and data-driven apps.

Flashing custom firmware can void warranty or fail on restricted devices. Confirm your Xteink X4 allows third-party flashing before using these artifacts. Keep a copy of official recovery/stock firmware if available for your hardware variant.

Rustmix X4 firmware
Screenshots

Interesting project - https://www.cnx-software.com/2026/04/26/lightink-an-esp32-based-solar-powered-e-ink-smartwatch-with-up-to-10-months-of-battery-life/

Daniel Ansorregui has developed LightInk, an open-source solar-powered E-ink watch inspired by 90s solar digital watches. It features a 1.54-inch e-paper display and supports Wi-Fi, Bluetooth, LoRa, and GPS, running on a 100mAh battery.

The project integrates a custom low-quiescent-power design using a TPS63900 buck-boost converter, capacitive-touch input, and deep-sleep-driven firmware, along with ultra-fast partial e-ink updates (<1 ms active time) and precise RTC timekeeping with drift calibration. It also supports solar-first operation (no dedicated charging IC) and dynamic power gating of peripherals, enabling around 9–10 months of operation on a small battery supplemented by solar power.

LightInk specifications:

• System-in-package – ESP32-PICO-D4 SiP
  • CPU – Dual-core processor @ 240MHz
  • Memory – 520KB SRAM
  • Storage – 4MB flash
  • Wireless – 2.4 GHz Wi-Fi 4 up to 150 Mbps and Bluetooth 4.2 BR/LE connectivity
• Display – 1.54-inch 200×200 B/W e-Paper panel (GDEH0154D67 or compatible)
• Audio – 10-15mm piezo electric disc speaker
• Connectivity
  • 2.4 GHz 802.11b/g/n Wi-Fi 4 and Bluetooth 4.2 BR/EDR via ESP32 SiP
  • LoRa via a Wio-SX1262 transceiver
  • GPS
• Misc
  • Capacitive touch buttons utilizing the ESP32’s internal touch pins
  • 3V 2.0 mm circular mini vibration motor
  • LED light pins
  • RTC with manual drift calibration (targeting 1ppm, currently at 10ppm)
• Power
  • TPS63900 buck-boost converter (1.8V to 5.5V, 75-nA IQ) operating dynamically at 2.6V/2.9V
  • Solar cell input
  • 100mAh battery
• Dimensions – TBD
• Enclosure – 3D printed

Github - https://github.com/DarkZeros/LightInk
Hackaday - https://hackaday.io/project/205564-lightink