This commit resolves critical stability issues causing WiFi file transfer
crashes in STA mode and adds aggressive performance optimizations for
maximum upload/download throughput.
CRITICAL BUG FIXES:
1. Fix use-after-free race condition in handleClient()
- Added atomic operations and mutex protection for server pointer
- Prevents store access fault crashes when stop() is called during handleClient()
- Root cause of the Guru Meditation Error in crash logs
- Location: src/network/CrossPointWebServer.cpp:135-158
2. Fix JSON buffer overflow in handleFileListData()
- Replaced 512-byte static buffer with dynamic allocation
- Safely handles 500-character filenames with JSON escaping
- Prevents stack corruption from oversized file entries
- Location: src/network/CrossPointWebServer.cpp:253-306
3. Convert static upload variables to thread-safe instance variables
- Moved uploadFile, uploadFileName, uploadPath, etc. to class members
- Added mutex protection to prevent concurrent access corruption
- Eliminates race conditions during uploads
- Location: src/network/CrossPointWebServer.h:44-54, CrossPointWebServer.cpp:311-313
4. Add yield() to handleClient loop
- Prevents WiFi stack starvation in STA mode
- Allows LWIP to process incoming packets and prevent buffer overflow
- Critical for stability during file transfers
- Location: src/activities/network/CrossPointWebServerActivity.cpp:304-311
5. Fix heap exhaustion with String pre-allocation
- Pre-allocate String capacities to avoid reallocations during upload
- Add heap threshold check (50KB minimum) before accepting uploads
- Reduces memory fragmentation
- Location: src/network/CrossPointWebServer.cpp:323-376
ROBUSTNESS IMPROVEMENTS:
6. Increase task stack size from 2KB to 6KB
- Prevents stack overflow during rendering + network operations
- Aligns with other display+network activity stack sizes
- Location: src/activities/network/CrossPointWebServerActivity.cpp:51
PERFORMANCE OPTIMIZATIONS:
7. Add LWIP TCP/IP stack optimizations
- Increased TCP MSS to 1436 bytes (optimized for WiFi)
- Increased send/receive buffers to 5744 bytes (4x MSS)
- Enlarged TCP/IP mailbox sizes for better packet handling
- Increased retransmission timeout to 3000ms (accommodates SD writes)
- Location: platformio.ini:31-49
8. Add WiFi performance optimizations
- Increased WiFi RX/TX buffer counts for better throughput
- Configured dynamic buffer allocation for optimal memory usage
- Enabled TCP window scaling and oversizing
- Location: platformio.ini:41-49
9. Maximize WiFi TX power
- Set WiFi TX power to maximum (19.5dBm) for best signal strength
- Improves throughput, especially at distance
- Applied to both STA and AP modes
- Location: src/network/CrossPointWebServer.cpp:58,
src/activities/network/CrossPointWebServerActivity.cpp:152,192
EXPECTED IMPACT:
- Eliminates WiFi file transfer crashes in STA mode
- Improves upload/download speeds by 2-3x through TCP optimizations
- Increases stability during large file transfers (>100MB)
- Better performance on weak WiFi signals
- Reduces heap fragmentation and memory pressure
TESTING RECOMMENDATIONS:
1. Test large file uploads (>50MB) in both STA and AP modes
2. Verify system stability during concurrent uploads
3. Monitor heap usage during file transfers
4. Test with long filenames (400+ characters)
5. Verify performance improvement with speed tests
Fixes: WiFi lockup bug causing Guru Meditation Errors during file transfer
## Summary
* **What is the goal of this PR?**
Fix file browser failing to navigate into subdirectories with non-ASCII
(Korean/Unicode) folder names.
* **What changes are included?**
- Enable UTF-8 long file names in SdFat (`USE_UTF8_LONG_NAMES=1`)
- Add directory validation before iterating files
- Add `rewindDirectory()` call for stability
## Additional Context
## Summary
* Swap to updated SDCardManager which uses SdFat
* Add exFAT support
* Swap to using FsFile everywhere
* Use newly exposed `SdMan` macro to get to static instance of
SDCardManager
* Move a bunch of FsHelpers up to SDCardManager
Using QRCode library from pio to generate the QR code.
Done:
- Display QR code for URL in network mode
- minor fixes of layout
- Display QR for URL in AP mode
- Display QR for AP in AP mode
---------
Co-authored-by: Dave Allie <dave@daveallie.com>
## Summary
* HTML files are now static, streamed directly to the client without
modification
* For any dynamic values, load via JSON APIs
* For files page, we stream the JSON content as we scan the directory to
avoid holding onto too much data
## Additional details
* We were previously building up a very large string all generated on
the X4 directly, we should be leveraging the browser
* Fixes https://github.com/daveallie/crosspoint-reader/issues/94
## Summary
- **What is the goal of this PR?**
Implements wireless EPUB file management via a built-in web server,
enabling users to upload, browse, organize, and delete EPUB files from
any device on the same WiFi network without needing a computer cable
connection.
- **What changes are included?**
- **New Web Server**
([`CrossPointWebServer.cpp`](src/CrossPointWebServer.cpp),
[`CrossPointWebServer.h`](src/CrossPointWebServer.h)):
- HTTP server on port 80 with a responsive HTML/CSS interface
- Home page showing device status (version, IP, free memory)
- File Manager with folder navigation and breadcrumb support
- EPUB file upload with progress tracking
- Folder creation and file/folder deletion
- XSS protection via HTML escaping
- Hidden system folders (`.` prefixed, "System Volume Information",
"XTCache")
- **WiFi Screen** ([`WifiScreen.cpp`](src/screens/WifiScreen.cpp),
[`WifiScreen.h`](src/screens/WifiScreen.h)):
- Network scanning with signal strength indicators
- Visual indicators for encrypted (`*`) and saved (`+`) networks
- State machine managing: scanning, network selection, password entry,
connecting, save/forget prompts
- 15-second connection timeout handling
- Integration with web server (starts on connect, stops on exit)
- **WiFi Credential Storage**
([`WifiCredentialStore.cpp`](src/WifiCredentialStore.cpp),
[`WifiCredentialStore.h`](src/WifiCredentialStore.h)):
- Persistent storage in `/sd/.crosspoint/wifi.bin`
- XOR obfuscation for stored passwords (basic protection against casual
reading)
- Up to 8 saved networks with add/remove/update operations
- **On-Screen Keyboard**
([`OnScreenKeyboard.cpp`](src/screens/OnScreenKeyboard.cpp),
[`OnScreenKeyboard.h`](src/screens/OnScreenKeyboard.h)):
- Reusable QWERTY keyboard component with shift support
- Special keys: Shift, Space, Backspace, Done
- Support for password masking mode
- **Settings Screen Integration**
([`SettingsScreen.h`](src/screens/SettingsScreen.h)):
- Added WiFi action to navigate to the new WiFi screen
- **Documentation** ([`docs/webserver.md`](docs/webserver.md)):
- Comprehensive user guide covering WiFi setup, web interface usage,
file management, troubleshooting, and security notes
- See this for more screenshots!
- Working "displays the right way in GitHub" on my repo:
https://github.com/olearycrew/crosspoint-reader/blob/feature/connect-to-wifi/docs/webserver.md
**Video demo**
https://github.com/user-attachments/assets/283e32dc-2d9f-4ae2-848e-01f41166a731
## Additional Context
- **Security considerations**: The web server has no
authentication—anyone on the same WiFi network can access files. This is
documented as a limitation, recommending use only on trusted private
networks. Password obfuscation in the credential store is XOR-based, not
cryptographically secure.
- **Memory implications**: The web server and WiFi stack consume
significant memory. The implementation properly cleans up (stops server,
disconnects WiFi, sets `WIFI_OFF` mode) when exiting the WiFi screen to
free resources.
- **Async operations**: Network scanning and connection use async
patterns with FreeRTOS tasks to prevent blocking the UI. The display
task handles rendering on a dedicated thread with mutex protection.
- **Browser compatibility**: The web interface uses standard
HTML5/CSS3/JavaScript and is tested to work with all modern browsers on
desktop and mobile.
---------
Co-authored-by: Dave Allie <dave@daveallie.com>
* First pass at moving to SDK EInkDisplay library
* Add 2-bit grayscale text and anti-aliased rendering of text
* Render status bar for empty chapters
* Refresh screen every 15 pages to avoid ghosting
* Simplify boot and sleep screens
* Give FileSelectionScreen task more stack memory
* Move text around slightly on Boot and Sleep screens
* Re-use existing buffer and write to whole screen for 'partial update'
* Add expat and swap out ERB HTML parser
* Increase EpubHtmlParserSlim file buffer to 1024 bytes
* Cleanup TextBlock functions
* Do not break words when leaving spans
