STM32 Nucleo standard

Status: draft, see issue 19296.

This page collects the rules that all STM32 Nucleo boards in NuttX follow. It starts with the common board initialization and grows as more of the board logic becomes shared.

Common board initialization

Initialization that does not depend on the board lives in boards/arm/common/stm32/src/board_common.c. It is part of the common STM32 board logic (CONFIG_ARCH_BOARD_COMMON), which every Nucleo board selects, and provides one function:

#include "board_common.h"

int stm32_common_initialize(void);

Every Nucleo board calls stm32_common_initialize() early in its bringup, in stm32_bringup() or, if the board has none, in board_late_initialize(). A failure is logged and the bringup continues.

The function currently handles:

Feature	Enabled by	Result
procfs	`CONFIG_FS_PROCFS`	mounted at `CONFIG_NSH_PROC_MOUNTPOINT` or `/proc`
tmpfs	`CONFIG_FS_TMPFS`	mounted at `CONFIG_LIBC_TMPDIR`
IWDG	`CONFIG_STM32_IWDG`	`/dev/watchdog0`
WWDG	`CONFIG_STM32_WWDG`	`/dev/watchdog1`
CAN	`CONFIG_STM32_CAN_CHARDRIVER` `CONFIG_STM32_FDCAN_CHARDRIVER`	`/dev/can0`, `/dev/can1`, … in instance order
SocketCAN	`CONFIG_STM32_CAN_SOCKET` `CONFIG_STM32_FDCAN_SOCKET`	interfaces for all enabled instances
I2C	`CONFIG_I2C_DRIVER`	`/dev/i2cN` for every enabled `CONFIG_STM32_I2CN`

The file systems are not mounted when CONFIG_DISABLE_MOUNTPOINT is set. The IWDG uses STM32_LSI_FREQUENCY from the board board.h.

Rules for boards:

Do not repeat any of the features above in the board directory.
Board-independent initialization is added to stm32_common_initialize(), not to individual boards.