Custom firmware for the Xteink X4 e-paper device. Turns a $70 e-ink reader into a smart device with wireless tools, security features, communication, games, and utilities — while keeping full e-reader functionality.
Forked from CrossPoint Reader. All core reading functionality comes from CrossPoint. Biscuit builds on top of it.
What is this
Biscuit treats the Xteink X4 as a general-purpose smart device, not just an e-reader. The home screen is a tile-based dashboard with live system info (battery, heap, uptime, WiFi status). Reading is one of eight categories, not the main focus.
The 4.26" e-ink display is readable in direct sunlight, retains its image without power, and gives the device days of battery life. Seven physical buttons provide navigation without a touchscreen. WiFi and BLE 5.0 enable wireless tools. A MicroSD card stores everything.
Hardware
Spec Value SoC ESP32-C3 (RISC-V, 160MHz) RAM 380KB SRAM (no PSRAM) Flash 16MB Display 4.26" 800×480 e-ink, 1-bit mono Input 7 buttons (4 front, 3 side) WiFi 2.4GHz 802.11 b/g/n BLE 5.0 (shared radio with WiFi) Storage MicroSD (FAT32) Port USB-C (serial + power)
Apps
The home screen is a dashboard of eight tiles. Everything lives under one of them.
Tile Purpose Recon Passive scanning and monitoring — no transmission Offense Active wireless testing, grouped into Scan → Profile → Attack → Capture Defense Stealth, detection, and device hardening Comms Communication and exchange Tools Crypto, network, productivity, and creative utilities Games Entertainment Reader Ebooks, OPDS, reading stats Settings Preferences, file transfer, system management
Recon — scan and monitor (passive only)
All apps in Recon are read-only — they listen but never transmit.
App What it does WiFi Scanner Discover APs and connected clients BLE Scanner Scan BLE devices, browse services and characteristics Full Sweep Combined WiFi + BLE passive scan Packet Monitor Monitor WiFi frames with PCAP recording Probe Sniffer Capture WiFi probe requests Wardriving Log access points with signal strength Crowd Density Estimate nearby people via probe request counting Device Fingerprint Identify device OS from probe request patterns Vendor Lookup Identify manufacturer by MAC (OUI database on SD) AP History Log visible access points over time to SD Network Change Snapshot nearby devices, compare for changes Perimeter Watch Alert when new devices appear in area BLE Proximity Track BLE device RSSI WiFi Heat Map RSSI mapping walkabout Signal Locator Estimate AP position via RSSI triangulation Deauth Detector Monitor for deauthentication frame spikes
Offense — active wireless testing
Offense opens a 2×2 sub-menu grouped into four phases. A disclaimer must be acknowledged before first use.
Scan — target discovery
App What it does WiFi Scan Discover APs and clients BLE Scan Discover BLE devices Full Sweep Combined WiFi + BLE passive scan Saved Targets Browse cached target database
Profile — target analysis
App What it does Target Profiler Select and analyze a target Client Enum Devices connected to target AP Host Scanner Find devices on local network Vuln Assessment Check encryption and WPS settings Signal Locator Estimate AP position from RSSI
Attack — broadcast and testing tools
App What it does Beacon Test Custom beacon broadcasting WiFi Test Wireless connectivity testing Captive Portal Network portal for testing Beacon Flood Broadcast 30 random SSIDs SSID Clone Clone a WiFi AP (open, same channel) BLE Spam Proximity / Fast Pair / Swift Pair flood BLE Keyboard HID keyboard emulation (DuckyScript over BLE) AirTag Test Device location testing USB Keyboard Wired DuckyScript over USB-C
Capture — review and export
App What it does Captured Data Handshakes, credentials, PCAPs, BLE logs Credential Viewer View credentials captured by portal Probe Log Recorded WiFi probe requests Scan History Browse previously found targets Wipe Captures Delete all captured data
Defense — stealth and protect
Ghost Mode is the headline entry — it rotates MAC, kills radios, and cleans up state in one action (replacing the old standalone MAC Changer and RF Silence apps).
App What it does Ghost Mode MAC rotate + RF kill + state cleanup, one shot Tracker Detector Detect AirTags, SmartTags, and Tiles following you Security Sweep Scan for cameras, trackers, rogue APs, skimmers Network Monitor Detect rogue APs and suspicious frames Emergency SOS SOS beacon (WiFi + BLE + Mesh) with dead man's switch Phone Tether BLE proximity disconnect alert Quick Wipe Erase all biscuit data from SD with verification PIN Security Lock device with PIN, duress PIN for fake profile Screen Decoy Fake screen to hide activity SD Encryption Encrypt biscuit data on SD with PIN
Comms — communicate and exchange
App What it does Mesh Chat ESP-NOW text chat, no WiFi needed, ~200m range, multi-hop relay SSID Channel Hide short messages in WiFi network names Contact Exchange Swap contact cards between devices via BLE Dead Drop Temporary WiFi AP for anonymous file exchange Bulletin Board Local anonymous message board via WiFi AP
Tools — utilities and productivity
A single tile that merges the old Network section with crypto, productivity, tracking, and creative apps.
Security & crypto
App What it does Authenticator TOTP 2FA codes, fully offline TOTP QR Show a 2FA code as a scannable QR Password Manager Encrypted credentials stored on SD Medical Card Emergency medical info persistent on e-ink Stego Notes Hide text inside BMP images
Network
App What it does WiFi Connect Join a WiFi network WiFi Scanner APs, signal, channels Host Scanner Find devices on local network Ping Ping a host or IP address DNS Lookup Resolve domain names HTTP Client Send GET/POST requests mDNS Browser Discover local services
Productivity
App What it does Clock NTP clock, stopwatch, pomodoro timer Calculator Basic calculator QR Generator Generate QR codes from text Morse Code Encode and decode morse Unit Converter Convert between measurement units Cipher Tools ROT13, Caesar, Vigenere, XOR OTP Generator One-time pad random number pages
Tracking & logging
App What it does Event Logger Timestamped notes with WiFi location tagging Flashcards Study decks loaded from CSV on SD Habit Tracker Daily habit checklist with streak tracking Breadcrumb Trail Record and retrace your path using WiFi fingerprints Vehicle Finder Find your parked car via WiFi fingerprint matching Transit Alert Alert when approaching a saved transit stop
Creative
App What it does Etch-A-Sketch Draw on the e-ink screen, save as BMP Barcode Generator Code 128 / Code 39 / EAN-13 Key Copier Draw key profiles from bitting codes WiFi QR Share Share WiFi credentials as a QR code File Browser Browse and view files on SD card Countdown Big countdown timer
Games
Casino (slots, blackjack, roulette, coin flip, higher/lower, loot box), Minesweeper, Sudoku, Chess (with bot), Snake, Tetris, Maze, Dice Roller, Game of Life, Voronoi, Matrix Rain.
Reader
App What it does Open Book Browse and open an ebook Recent Books Continue where you left off OPDS Browser Download books from OPDS servers Reading Stats Pages read, books completed, streaks Browse Files File manager for the SD card
Full EPUB 2/3 rendering, KOReader Sync, and Calibre wireless transfer are inherited from CrossPoint.
Settings — system and configuration
Promoted to a top-level tile from the old System section.
App What it does Settings Display, reader, controls, system configuration WiFi Transfer Upload/download files via WiFi (STA, AP, or Calibre) USB Storage Share the SD card as a USB mass-storage drive Task Manager View heap, uptime, and activity stack Battery Battery level with history graph Device Info Chip, flash, RAM, firmware, WiFi, screen info Background Radio state, SD status, active timers Automation WiFi geofence triggers and scheduled tasks
Themes
Three UI themes, selectable in Settings:
Classic — original CrossPoint style
— original CrossPoint style Lyra — rounded elements, modern feel (default)
— rounded elements, modern feel (default) Military — inverted headers, sharp corners, dashed separators, uppercase labels
SD card structure
/biscuit/ portals/ # HTML templates for captive portal ducky/ # DuckyScript files for HID keyboard pcap/ # Packet captures scans/ # Network scan results logs/ # WiFi/BLE scan logs, AP history, event logs drawings/ # Etch-A-Sketch saved BMPs trails/ # Breadcrumb trail data snapshots/ # Network change snapshots flashcards/ # Flashcard decks (CSV) creds.csv # Captured portal credentials medical.dat # Medical card info totp.dat # TOTP authenticator secrets (encrypted) casino.dat # Casino credits habits.dat # Habit tracker data security.dat # PIN hashes automation.dat # Automation rules oui.txt # IEEE OUI vendor database (user-provided)
Installing
Web flasher (recommended)
Connect your Xteink X4 via USB-C data cable (not charge-only) Wake the device by pressing Power Go to https://xteink.dve.al/ and flash the firmware
To revert to stock firmware, use the same site or press "Swap boot partition" at https://xteink.dve.al/debug.
Manual
git clone --recursive https://github.com/yattsu/biscuit cd biscuit pio run --target upload
Development
Prerequisites
PlatformIO Core or VS Code + PlatformIO IDE
Python 3.8+
USB-C data cable
Xteink X4
Building
# Windows PowerShell $ env: PYTHONUTF8 = 1 pio run - j 16
# Linux / macOS pio run -j 16
Adding translations
Translations live in lib/I18n/translations/ . Each language is a YAML file. Add or edit strings, then regenerate:
python3 scripts/gen_i18n.py lib/I18n/translations lib/I18n/
See i18n docs for details.
Debugging
python3 -m pip install pyserial colorama matplotlib python3 scripts/debugging_monitor.py
The debug monitor shows color-coded logs and a real-time memory graph.
Architecture
The firmware uses an activity-based UI architecture. Every screen is an Activity subclass with onEnter() , loop() , render() , and onExit() . Activities are managed by ActivityManager (push/pop/replace). WiFi and BLE share one radio, arbitrated by RadioManager .
See architecture docs for the full overview.
Upstream
Biscuit tracks CrossPoint Reader as upstream. To sync:
git remote add upstream https://github.com/crosspoint-reader/crosspoint-reader.git git fetch upstream git merge upstream/master
Credits
Built on CrossPoint Reader by the CrossPoint contributors. CrossPoint was inspired by diy-esp32-epub-reader by atomic14.
License
MIT