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Jul 31, 2026 10:32 PM UTC
Solved

Using Nucleo ST-LINK-V3 to debug external STM32

Greetings! A custom H523-based board has a 4-header connector [3.3V, SWDIO, SWCLK, GND] that I used with an external STLINK-V2 dongle connected to my laptop. Is it possible to debug this board using STLINK-V3 on my NUCLEO-U545RE-Q? Section 7.3 of the manual, Embedded STLINK-V3EC, does not mention this. Thanks.

AScha.3
AScha.3Best answer
Super User
Aug 1, 2026 7:50 AM UTC

Hi,

 

short: no.

long: this nucleo series with st-link V3 have debug connector, but just to connect external debug to the nucleo:

So you have to cut some connections and disable U545 nucleo cpu , to use the connector signals as debug of another cpu.

Possible - but probably not worth the effort, as a V3 miniE  or mods is just about 10 eu :

 

On the V3 mods you have to solder a connector or just some wires to connect to the [3.3V, SWDIO, SWCLK, GND] .

If you feel a post has answered your question, please click on " Best Answer ".

5 replies

Richard Li
Senior
Jul 31, 2026 11:57 PM UTC

You can use CN2, you can looking for schematics. 

Richard Li
Senior
Aug 1, 2026 12:40 AM UTC

Sorry, this board can’t use CN2.

AScha.3
AScha.3Best answer
Super User
Aug 1, 2026 7:50 AM UTC

Hi,

 

short: no.

long: this nucleo series with st-link V3 have debug connector, but just to connect external debug to the nucleo:

So you have to cut some connections and disable U545 nucleo cpu , to use the connector signals as debug of another cpu.

Possible - but probably not worth the effort, as a V3 miniE  or mods is just about 10 eu :

 

On the V3 mods you have to solder a connector or just some wires to connect to the [3.3V, SWDIO, SWCLK, GND] .

If you feel a post has answered your question, please click on " Best Answer ".
Andrew Neil
Super User
Aug 1, 2026 1:10 PM UTC

Section 7.3 of the manual, Embedded STLINK-V3EC, does not mention this

If it were possible, the manual would document how to do it.

The manual doesn’t mention it because it’s not possible*.

 

This is a change of direction from the original Nucleo - which did support using the built-in ST-Link to program/debug an external target.

However, that always came with some limitations & pitfalls - so I’ve always said it’s far better to just get a standalone STLink!

For example:

 

 

* Of course, it is possible by hacking the PCB - but, as ​@AScha.3 said, unlikely to be worth the effort.

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.
Aug 1, 2026 2:24 PM UTC

Got it, thanks!