Configure UART3 on NUCLEO-H7S3L8 Board for use with ST-Link VCP

Shreayas_Acharaya · ‎2024-11-25

Title edited to reflect the correct board used. Changed from NUCLEO-H7A3ZI-Q to NUCLEO-H7S3L8.

Hi,
I’m trying to set up UART communication using UART3 on the NUCLEO-H7A3ZI-Q board. I have the UART3 pins (PD8 and PD9) connected to the ST-Link VCP on this board.

Do I need an external USB-UART converter to communicate through other UART pins, or should the onboard ST-Link handle the UART3 communication through VCP?
It's showing USART3 is not available.

I’m new to this board, so I want to confirm if there’s anything I might be missing in the configuration or connections. Any guidance would be appreciated!

Thanksin advance!

SofLit · ‎2024-11-27

Hello,

As a workaround, go to the Bsp menu and activate the Virtual Com port then deactivate it , then go back to USART3 under connectivity and you will be able to configure it.

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SofLit · ‎2024-11-25

Hello,

If you want to use USART with PD8/PD9 with STLINK virtual comport no need to use external USB/UART bridge.

But if you need to change to other IOs using an external USB/UART bridge is a must.

But there is a workaround: you can use USART3 with other IOs and using STLINK-VCP by wiring the Tx connected to the VCP to the new Tx. Same for Rx.

Attached an ioc file where USART3 is enabled on NUCLEO-H7A3ZI-Q board.

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Andrew Neil · ‎2024-11-26

@SofLit wrote:
If you want to use USART with PD8/PD9 with STLINK virtual comport no need to use external USB/UART bridge.
But if you need to change to other IOs, using an external USB/UART bridge is a must.

@Shreayas_Acharaya See this post:

https://community.st.com/t5/stm32-mcus-products/stm32f4-nucleo-f429zi-unable-to-communicate-with-hmi-via-rs232/m-p/747246/highlight/true#M267271

It explains when the ST-Link's VCP can be used, and when a separate USB-to-UART converter is required.

(It is for a different board, but the same principles apply)

Shreayas_Acharaya · ‎2024-11-26

Hi SofLit,

Apologies for the confusion earlier. I realized I misstated the board model—I'm actually working with the NUCLEO-H7S3L8.

I'm facing difficulties setting up UART communication for this board. The settings in the .ioc file seem different, and I'm unclear on how to proceed with UART printing. I'm referencing the user manual for guidance but still finding it a bit unclear.

Could you clarify if I need an external USB-UART converter for UART communication on this board? Or should I rely solely on the onboard ST-Link for VCP functionality?

I am not able to do mode configuration.

Thanks for your help and patience!

SofLit · ‎2024-11-27

Hello,

Check out the UART (printf) example provided in STM32H7RS Cube package for NUCLEO-H7S3L8 board: package: https://github.com/STMicroelectronics/STM32CubeH7RS/tree/main/Projects/NUCLEO-H7S3L8/Examples/UART/UART_Printf

There is an ioc file available for this example. You need to read the readme file to run the example.

Hope it helps.

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Andrew Neil · ‎2024-11-27

@Shreayas_Acharaya wrote:
Could you clarify if I need an external USB-UART converter for UART communication on this board?

What is unclear about this:

It clearly tells you that UART3, using pins PD8 and PD9, is connected to the ST-Link's Virtual COM Port (VCP).

The ST-Link's Virtual COM Port (VCP) is a USB-to-UART bridge; it is built into the Nucleo board precisely so that you do not have to add any external USB-to-UART bridge to communicate via UART3 on pins PD8 and PD9.

Conversely, if you use UART3 (or any other UART) on any other pins, they will not be connected to the ST-Link's Virtual COM Port (VCP) and, therefore, you will have to add an external USB-to-UART bridge.

PS:

https://www.st.com/resource/en/user_manual/um3276-stm32h7rx7sx-nucleo144-board-mb1737-stmicroelectronics.pdf#page=9

Shreayas_Acharaya · ‎2024-11-27

Thank you,
But why am I not able to select the UART mode configuration in the IOC?

Also, please clarify what this mean:

SofLit · ‎2024-11-27

@Shreayas_Acharaya wrote:

But why am I not able to select the UART mode configuration in the IOC?

Because simply (I think) you've already enabled USART3 as Virtual Comport at the project creation:

If it is the case, USART3 is ready for usage and you don't need to configure it.

@Shreayas_Acharaya wrote:

Also, please clarify what this mean:

@Andrew Neil already explained it in details in his last comment.

Hope it helps.

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Andrew Neil · ‎2024-11-27

@Shreayas_Acharaya wrote:
Also, please clarify what this mean:

Again, what part(s) of that, exactly, do you find unclear?

What part(s) of the explanation in my previous reply was unclear?

SofLit · ‎2024-11-27

I tried to create a project starting from a board: NUCLEO-H7S3L8 with virtual comport disabled at the project creation:

But UART3 still disabled:

So I think it's a limitation. Will be escalated internally for analysis.

Internal ticket 197144 for follow-up.

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