T-Box Hardware Overview
T-Box is the optional BYD EV Pro hardware/firmware component. The firmware repository is ev-pro-tbox; it contains BLE, Cloud, modem, GPS, proximity, OTA, diagnostics, and command-dispatcher modules. These docs describe verified software behavior; product-approved hardware packaging and installation instructions are still open.
What T-Box adds
Section titled “What T-Box adds”Confirmed by source:
- BLE pairing/provisioning with the Car App.
- Cloud connectivity and per-device command topics.
- T-Box state/data/log/info publishing.
- GPS collection through the modem GPS module.
- BLE proximity scanning, RSSI filtering, HMAC token verification, challenge/response, and lock/unlock action logic.
- OTA firmware update support, including BLE OTA from the Car App and Cloud OTA modules.
- Diagnostic logging and Cloud log publishing.
What works without T-Box
Section titled “What works without T-Box”- Car App dashboard and local controls while the head unit is running.
- Companion App car-only QR pairing.
- Home Assistant webhook pushes from the Car App.
What requires T-Box
Section titled “What requires T-Box”- Proximity auto-lock/unlock.
- T-Box GPS breadcrumbs/state.
- T-Box command routing through
tbox/cmd/.... - T-Box firmware update delivery.
- T-Box diagnostics and logs.
Requirements before setup
Section titled “Requirements before setup”- Product-approved physical installation, power, wiring, fuse, and placement instructions.
- A powered T-Box that advertises over BLE with a name like
EVP-tbox-XXXXXX. - Car App access to the relay so per-device Cloud credentials can be created.
- Car App/head-unit BLE access during provisioning and BLE OTA updates.
- Confirmed cellular/SIM/eSIM or other network path for modem-backed Cloud/GPS behavior.
TODO: Product clarification needed — Which T-Box hardware revision, connector, power input, fuse rating, placement, and safety limits should public docs require before setup?
Pairing and provisioning
Section titled “Pairing and provisioning”The Car App pairing wizard scans for Bluetooth devices named like EVP-tbox-XXXXXX. It derives a tbox-XXXXXX identifier, creates per-device Cloud credentials through the relay, sends a shared secret and credentials to the T-Box over BLE, then waits for the T-Box to reboot and identify itself again.
If Cloud credentials cannot be created, the wizard fails instead of falling back to old compiled credentials.
Connectivity
Section titled “Connectivity”The firmware includes modem PPP, Cloud, WebSocket, and GPS modules. The public docs should not promise a bundled SIM card, a specific mobile operator, or a user data plan policy until product packaging is confirmed.
TODO: Product clarification needed — Does the shipped T-Box include a SIM/eSIM and data service, and what should users do if cellular service is unavailable?
Status indicators
Section titled “Status indicators”The current led_status.c file says T-Box v2 has no status LED on board and preserves the LED API as no-op functions. Older draft LED blink tables are not valid for v2 hardware.
TODO: Product clarification needed — Are there any user-visible indicators on shipping T-Box hardware besides app-reported status?
Firmware updates
Section titled “Firmware updates”The Car App contains a T-Box OTA flow that checks for an update, downloads firmware, verifies SHA-256, streams chunks over BLE, waits for installation confirmation, and handles reboot/reconnect state.
Installation
Section titled “Installation”TODO: Product clarification needed — What physical installation, wiring, fuse, and placement instructions are approved for public documentation?
Until that is clarified, these docs only describe software behavior verified in the repository.