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Merged
cederom merged 1 commit into from
Apr 21, 2026
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boards/arm/stm32: route nucleo-f412zg console through ST-LINK VCP. #18766

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57 changes: 32 additions & 25 deletions Documentation/platforms/arm/stm32f4/boards/nucleo-f412zg/index.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -123,7 +123,8 @@ Pins and Connectors::
TXD: PA2 CN9 pin 2(See SB13, 14, 62, 63). CN10 pin 35
PD5

UART2 is the default in all of these configurations.
USART2 is available on the board headers. It is not the default ``nsh``
console path.

TTL to RS-232 converter connection::

Expand Down Expand Up @@ -153,6 +154,30 @@ To configure USART2 as the console::
CONFIG_USART2_PARITY=0
CONFIG_USART2_2STOP=0

USART3
------

Pins and Connectors::

RXD: PD9
TXD: PD8

By default the board solder bridges connect USART3 to the on-board
ST-LINK Virtual COM Port. This is the default ``nsh`` console path in
NuttX.

To configure USART3 as the console::

CONFIG_STM32_USART3=y
CONFIG_USART3_SERIALDRIVER=y
CONFIG_USART3_SERIAL_CONSOLE=y
CONFIG_USART3_RXBUFSIZE=256
CONFIG_USART3_TXBUFSIZE=256
CONFIG_USART3_BAUD=115200
CONFIG_USART3_BITS=8
CONFIG_USART3_PARITY=0
CONFIG_USART3_2STOP=0

USART6
------

Expand All @@ -178,28 +203,10 @@ To configure USART6 as the console::
Virtual COM Port
----------------

Yet another option is to use UART2 and the USB virtual COM port. This
option may be more convenient for long term development, but is painful
to use during board bring-up.

Solder Bridges. This configuration requires:

- SB62 and SB63 Open: PA2 and PA3 on STM32 MCU are disconnected to D1
and D0 (pin 7 and pin 8) on Arduino connector CN9 and ST Morpho
connector CN10.

- SB13 and SB14 Closed: PA2 and PA3 on STM32F103C8T6 (ST-LINK MCU) are
connected to PA3 and PA2 on STM32 MCU to have USART communication
between them. Thus SB61, SB62 and SB63 should be OFF.

Configuring USART2 is the same as given above.

Question: What BAUD should be configure to interface with the Virtual
COM port? 115200 8N1?

Default:
As shipped, SB62 and SB63 are open and SB13 and SB14 closed, so the
virtual COM port is enabled.
The NUCLEO-F412ZG ST-LINK virtual COM port is connected to USART3 on
PD8/PD9. As shipped, the default solder bridge configuration enables
this routing, so the default ``nsh`` configuration uses USART3 for the
console.

Configurations
==============
Expand All @@ -208,8 +215,8 @@ nsh
---

Configures the NuttShell (nsh) located at apps/examples/nsh for the
Nucleo-F410RB board. The Configuration enables the serial interfaces
on UART2. Support for builtin applications is enabled, but in the base
Nucleo-F412ZG board. The configuration enables the serial interfaces
on USART3. Support for builtin applications is enabled, but in the base
configuration no builtin applications are selected (see NOTES below).

NOTES:
Expand Down
1 change: 1 addition & 0 deletions arch/arm/src/stm32/Kconfig
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Expand Up @@ -1686,6 +1686,7 @@ config STM32_STM32F412
select STM32_HAVE_TIM12
select STM32_HAVE_TIM13
select STM32_HAVE_TIM14
select STM32_HAVE_USART3
select STM32_HAVE_USART2
select STM32_HAVE_USART6
select STM32_HAVE_I2C1
Expand Down
4 changes: 2 additions & 2 deletions boards/arm/stm32/nucleo-f412zg/configs/nsh/defconfig
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Expand Up @@ -51,9 +51,9 @@ CONFIG_STM32_DISABLE_IDLE_SLEEP_DURING_DEBUG=y
CONFIG_STM32_FLASH_PREFETCH=y
CONFIG_STM32_JTAG_SW_ENABLE=y
CONFIG_STM32_SERIAL_DISABLE_REORDERING=y
CONFIG_STM32_USART2=y
CONFIG_STM32_USART3=y
CONFIG_SYSTEM_NSH=y
CONFIG_TASK_NAME_SIZE=32
CONFIG_TIMER=y
CONFIG_USART2_SERIAL_CONSOLE=y
CONFIG_USART3_SERIAL_CONSOLE=y
CONFIG_USEC_PER_TICK=1000
8 changes: 8 additions & 0 deletions boards/arm/stm32/nucleo-f412zg/include/board.h
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Expand Up @@ -125,6 +125,14 @@
# define GPIO_USART2_RX GPIO_USART2_RX_2
# define GPIO_USART2_TX GPIO_USART2_TX_2

/* USART3 (ST-LINK Virtual COM Port):
* RXD: PD9
* TXD: PD8
*/

# define GPIO_USART3_RX GPIO_USART3_RX_3
# define GPIO_USART3_TX GPIO_USART3_TX_3

/* USART6:
* RXD: PG9 CN10 pin 16
* TXD: PG14 CN10 pin 14
Expand Down
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