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feat(esp32): add ESP32-S3 USB bridge backend - #201
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cheetahdotcat wants to merge 7 commits into
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cheetahdotcat wants to merge 7 commits into
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Add BackendKind::esp32_bridge. An ESP32-S3 running the bridge firmware enumerates as a composite USB device: a CDC-ACM control port plus two slots that hold an XInput pad, a HID pad (DualSense, DualShock 4, Switch Pro), or a shared keyboard and mouse. The host binds its inbox drivers. - Wire protocol (esp32_bridge_protocol.h) shared with the firmware: COBS frames with CRC-16, layout transactions, input and output reports, keepalive. The bridge re-enumerates on every layout change; the client reopens the port, restores the desired layout after resets, and replays the latest gamepad report. - platform_default switches to an attached bridge (USB serial LVHB-*), LVH_ESP32_PORT, or LVH_BACKEND=esp32_bridge unless Esp32BridgeOptions::autodetect is false; gamepads fall back to the platform backend when an implicitly selected bridge does not answer. - Pairing: the bridge accepts layout and input frames only from hosts that answer an HMAC-SHA256 challenge with a secret it issued after a press of its BOOT button. Secrets are stored per bridge in a file only its owner (and SYSTEM/Administrators on Windows) can read. POSIX ports are opened with TIOCEXCL. - lvh::find_esp32_bridge_ports() and lvh::esp32_bridge_status() report attached bridges and the connection and pairing state without opening a port. - Build lizardbyte-common's env helper on every platform.
Use small structs for the key usage tables instead of std::pair built from int literals (MSVC C4244), and a string_view for the auth context instead of pointer arithmetic on a literal (-Wstring-plus-int).
Build the fixed-size auth message and AUTH payload as arrays and the keyboard/mouse descriptor with a sized vector instead of repeated vector::insert calls.
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9 of 18 tasks
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- Replace the C protocol header with a C++ one (constexpr constants, std::span, std::optional frame decoding); the firmware keeps a C copy. - Group BridgeClient state into per-mutex structs and move the frame handlers onto the connection state. - Split frame accumulation out of the reader loop. - Use std::byte for bit manipulation, std::format for messages, and std::array instead of C arrays. - Split the fake firmware's frame handler in the tests and create test directories below the working directory.
A layout change waited for a session that reported the new generation. If the bridge reset again before the waiting thread woke up, the wait ran into the re-enumeration timeout while holding the layout lock, which also delayed restoring the layout after the reset. Record the last generation a usable session reported and wait for that instead.
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Description
Adds
BackendKind::esp32_bridge: devices are created on an ESP32-S3 connected to the host over USB. The board runs separate firmware (esp32s3-hid-bridge) and enumerates as a composite USB device with a CDC-ACM control port and two device slots. The host binds its inbox drivers (xusb22for XInput, the HID class driver otherwise).Device : https://www.seeedstudio.com/XIAO-ESP32S3-p-5627.html
XUSB10compatible ID).src/platform/esp32/esp32_bridge_protocol.h, plain C, shared with the firmware):platform_defaultswitches to an attached bridge (USB serialLVHB-*),LVH_ESP32_PORT, orLVH_BACKEND=esp32_bridge. Consumers that offer the bridge as an explicit choice setEsp32BridgeOptions::autodetect = false. If the bridge was selected implicitly and does not answer, gamepads fall back to the platform backend.TIOCEXCL.Esp32BridgeOptions(RuntimeOptions::esp32_bridge)lvh::find_esp32_bridge_ports()lvh::esp32_bridge_status(): connection and pairing state, without opening a portenv.cppis now compiled on every platform (it was Windows-only) for the environment lookups.docs/esp32-bridge.md, plus a row indocs/platform-support.md.Screenshot
Not applicable: no UI changes.
Issues Fixed or Closed
None.
Roadmap Issues
None.
Testing
New tests:
tests/unit/test_esp32_bridge.cpphas 48 tests against an in-memory firmware model. They cover:stop()during a pending layout, and teardown while output reports arriveTIOCEXCLon a pty (Linux)Runs:
Hardware:
hid-playstation, and lightbar and rumble outputs reach the callback.xusb22binding in the composite device, and multi-monitor absolute pointer mapping.Type of Change
Checklist
AI Usage
See our AI usage policy.
Model: Claude Opus 5.5 (
claude-opus-5-5) via Claude Code, used for implementation, tests, and drafting this description. The author reviewed the changes and tested them on hardware.