0005. Portable drivers/ separate from board-specific bsp/

• Status: Accepted
• Date: 2026-10-27 (renamed from platform/ to bsp/ the same day)

Context

The firmware runs today on the NUCLEO-WB55 + IKS4A1 bench, with the IMU on I²C. Next it runs on the ACwing FC rev A, with the IMU on SPI and I²C1 used only for the expansion bus. A single "drivers" folder was proposed.

Decision

Two folders, with a clear boundary:

Folder	Content	Depends on
App/drivers/	chip drivers: LSM6DSV16X (with the sensor hub), VL53L1X, flow bridge	only the sensor_bus_t / vl53_bus_t function pointers
App/bsp/	board support: HAL I²C + DMA binding and bus lock, Qwiic binding, BLE GATT service, flash pages shared with CPU2	STM32 HAL, FreeRTOS, STM32_WPAN

Task logic that used to sit in the binding moved to app/. For example, the ExtTask probing and polling is now app/ext_sens.c, and its HAL binding is bsp/ext_i2c.c.

Consequences

• Everything in drivers/ builds in the host tests. Nothing in bsp/ does, and that is visible from the folder alone.
• The port to the ACwing FC rev A changes bsp/ (and the CubeMX project), not the drivers.
• Cost: one more folder, and a binding function per bus.

Alternatives considered

• One flat drivers/ folder. Simpler to browse, but it hides which code can be tested without the board.
• drivers/chips + drivers/stm32. The same boundary under one folder. It was judged equivalent, and bsp is the usual embedded name for the second part.