Biscuit Firmware Turns Xteink X4 E‑Paper Reader into a Smart Device
Explore Biscuit firmware to assess security hardening for IoT devices.
Test the firmware on Xteink X4 to verify WiFi/BLE coexistence and security features.
Summary
Biscuit is a custom firmware that transforms the $70 Xteink X4 e‑ink reader into a full‑featured smart device while preserving its core reading functions. Forked from CrossPoint Reader, Biscuit adds a tile‑based dashboard that displays live system data such as battery, heap, uptime, and WiFi status, and re‑organises reading into one of eight categories rather than the main focus.
The firmware runs on an ESP32‑C3 SoC (160 MHz, 380 KB SRAM, 16 MB Flash) with a 4.26" 800×480 1‑bit e‑ink display, seven physical buttons, WiFi 2.4 GHz 802.11 b/g/n, BLE 5.0, MicroSD storage, and a USB‑C serial port. It offers passive recon tools (WiFi/BLE scanners, packet monitor, probe sniffer, crowd density estimate), active offense utilities (beacon test, beacon flood, BLE spam, USB HID emulation), defense features (Ghost Mode, tracker detector, security sweep, SOS beacon), communication options (ESP‑NOW mesh chat, contact exchange, dead drop), and a suite of utilities and games.
Biscuit also includes crypto and productivity apps such as a TOTP authenticator, password manager, medical card, steganography, QR generator, and a file browser, as well as a reader that supports EPUB 2/3, OPDS, and Calibre sync. The firmware can be flashed via the Xteink web flasher or PlatformIO, and the source is fully open‑source on GitHub.
Key changes
- Tile‑based dashboard shows battery, heap, uptime, WiFi status
- Passive recon tools include WiFi/BLE scanners, packet monitor, probe sniffer, crowd density estimate
- Active offense utilities provide beacon test, beacon flood, BLE spam, USB HID emulation
- Defense features include Ghost Mode (MAC rotate, RF kill, state cleanup) and tracker detector
- Communication options add ESP‑NOW mesh chat, contact exchange, dead drop
- Crypto utilities include TOTP authenticator, password manager, medical card, steganography
- Games and utilities such as Etch‑A‑Sketch, casino, flashcards, habit tracker
- Firmware runs on ESP32‑C3 with 4.26" e‑ink display, 7 buttons, WiFi/BLE, MicroSD, USB‑C