debugger via UART without ST-LINK on NUCLEO-H755ZI-Q

Domy_ST · ‎2026-04-16

hello ST Community!

I'm trying to connect via UART without USB ST-LINK to the NUCLEO-H755ZI-Q for debugging from the STM32CubeIDE environment, but I can't connect.

What settings do I need to make in the STM32CubeIDE environment to debug via UART?

I tried connecting via UART from the STM32CubeProgrammer environment to simply read flash memory, but it won't connect.

What settings do I need to make in the STM32CubeIDE environment to debug via UART without USB ST_LINK?

Thanks for supports

Andrew Neil · ‎2026-04-16

@Domy_ST wrote:
I would like to do full debugging via UART because in the future the Nucleo-H755ZI-Q microcontroller will be integrated into a board .

You realise that integrating ST Development boards into a final product is not allowed?

See the Terms of Use (via: https://www.st.com/en/evaluation-tools/nucleo-h755zi-q.html#documentation)

@Domy_ST wrote:
I'm not sure if I will have access to the SWD using the STDC14 - MIPI10 connector.

How to do this is described in the User Manual:

https://www.st.com/resource/en/user_manual/um2408-stm32h7-nucleo144-boards-mb1363-stmicroelectronics.pdf#page=17

also via: https://www.st.com/en/evaluation-tools/nucleo-h755zi-q.html#documentation

A complex system that works is invariably found to have evolved from a simple system that worked.
A complex system designed from scratch never works and cannot be patched up to make it work.

View solution in original post

mƎALLEm · ‎2026-04-16

Hello,

@Domy_ST wrote:

I tried connecting via UART from the STM32CubeProgrammer environment to simply read flash memory, but it won't connect.

What do you mean by connecting UART from CubeProgrammer? do you mean via ST bootloader?

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Domy_ST · ‎2026-04-16

hello @mƎALLEm,

Yes, using the ST Bootloader via UART, you don't want to connect to the STm32CubeProgrammer, as described in this post:

https://community.st.com/t5/stm32cubeprogrammer-mcus/connection-via-uart-with-stm32cubeprogrammer/td-p/892681

In addition to the ST Bootloader via UART, I also need to debug via UART without USB. ST-LINK with the STM32CubeIDE environment is this possible?

Andrew Neil · ‎2026-04-16

What do you mean by, "debugging" here?

Are you simply looking to give printf-style outputs, or do you want the full control that SWD/JTAG provides?

SWD/JTAG gives a direct connection to the chip's internal debug hardware - you can't do that via UART.

The closest would be to implement some sort of Debug Monitor; eg,

Step-through debugging with no debugger on Cortex-M

But, if you can provide a UART connection - why not provide a SWD connection? It only needs* 2 wires (plus ground)...

* Although 4 is better - including NRST and VDD

A complex system that works is invariably found to have evolved from a simple system that worked.
A complex system designed from scratch never works and cannot be patched up to make it work.

mƎALLEm · ‎2026-04-16

@Domy_ST wrote:

Yes, using the ST Bootloader via UART, you don't want to connect to the STm32CubeProgrammer, as described in this post:

https://community.st.com/t5/stm32cubeprogrammer-mcus/connection-via-uart-with-stm32cubeprogrammer/td-p/892681

Did you use the same resource needed by the UART that are indicated in the AN2606 "Introduction to system memory boot mode on STM32 MCUs"?

USART3 needs PB11 and PB10 for the bootloader:

While in the NUCLEO board is connected to PD8 and PD9 as indicated by the schematic:

So you need to wire and connect PB10 to PD8 and PB11 to PD9, so the STLINK-VCP will be connected to the USART3 and use the ST bootloader.

@Domy_ST wrote:

In addition to the ST Bootloader via UART, I also need to debug via UART without USB. ST-LINK with the STM32CubeIDE environment is this possible?

Not clear what do you mean by debug with UART in CubeIDE!

Do you need to display messages over printf in CubeIDE or you need totally to debug the application with UART?? Because that's not possible as it doesn't make sense.

To display messages over UART using printf you need to make a retarget of UART to printf.

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Andrew Neil · ‎2026-04-16

@Domy_ST wrote:
In addition to the ST Bootloader via UART, I also need to debug via UART without USB. ST-LINK with the STM32CubeIDE environment is this possible?

That's really two separate questions.

It would have been better to keep the other thread for the bootloader access, and have a separate one for the debug-over-UART question.

A complex system that works is invariably found to have evolved from a simple system that worked.
A complex system designed from scratch never works and cannot be patched up to make it work.

Domy_ST · ‎2026-04-16

The ST Bootloader worked by making the connections you indicated. Thank you very much!

Yes, I know how to use printf debugging via UART. My intention was to do full debugging via UART. If you tell me that's not possible, I'll just use printf debug monitor. Or maybe something can be done as you say @Andrew Neil .

Domy_ST · ‎2026-04-16

@Andrew Neil Yes, I know how to use the printf monitor debug via UART. My intention was to fully debug via UART. If you tell me that's not possible, I'll just use the printf monitor debug and take a look at the link you provided.

Thanks

Andrew Neil · ‎2026-04-16

@Domy_ST wrote:
The ST Bootloader worked by making the connections you indicated. .

~~You've marked the solution in the wrong thread!~~

~~Keep this one about the debug-over-UART question.~~

~~How to unmark a solution.~~

EDIT: now fixed.

@Domy_ST wrote:
My intention was to do full debugging via UART. If you tell me that's not possible

No, that's not what I said.

@Domy_ST wrote:
maybe something can be done as you say @Andrew Neil .

Yes - I gave a link to an example.

But it still leaves the question of why you want to do that?

Why not just use SWD as god intended?

PS:

Note that it is possible to do SWD debugging remotely, if that's what you're worried about:

A complex system that works is invariably found to have evolved from a simple system that worked.
A complex system designed from scratch never works and cannot be patched up to make it work.

mƎALLEm · ‎2026-04-16

I've already said that.

@mƎALLEm wrote:

Do you need to display messages over printf in CubeIDE or you need totally to debug the application with UART?? Because that's not possible as it doesn't make sense.

To display messages over UART using printf you need to make a retarget of UART to printf.

So not possible to debug your application over UART. So I suppose the question has been answered.

You need definitely a STLINK or JTAG or Trace probe connected to the core to debug the application.

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