Arm Mbed OS support forum

32pin Nucleo Boards - ST Poor Design , Engineers Not Thinking!

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From my point of view the Nucleo 32 board has probably similar format like Arduino nano, so there can be limitation of size. That is probably a reason why ST not include this things.

In other hand, both (Nucleo 32 and ST-link) are ST’s products and of course they want to promote the brand.

What is the function of SWD CN2 header in Nucleo 32 board ?

However, you probably mistaken the forum. I do not understand what your personal idea about ST’s design has to do with ARM Mbed. So take relax and then visit and discuss your idea with them, but I am sure, with this tone (toxic), no one will want to communicate with you.

BR, Jan

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This post was flagged by the community and is temporarily hidden.

It seems, you are not

so now try to find your way to the right forum. Bye!

Have a nice day, Jan

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Hello John,

I understand your frustration. No one and nothing is perfect. But it doesn’t mean that everyone and everything is wrong! Unfortunately, I don’t have an STM32 Nucleo-32 board to test it but according to Table 4. “External power sources” shown in the user manual (Chapter 6.4.2 “External power supply inputs”), ST-LINK is not powered when the board is supplied from an external 5V source over pin 4 on the CN4 connector. I’m not sure, but maybe in such case debugging with an external probe (e.g. Segger Debugger) might work over the CN2 ST-LINK SWD connector (once installed) even without having the ST-LINK completely isolated.

And please don’t blame Jan! He is spending his private time to help others without any reward. I think he deserves much more, but we should say at least “Thank you Jan”!

EDIT: Sorry, I was also wrong! After checking the electrical schematics it seems that the ST-LINK is powered also when the board is supplied from an external source. The information in Table 4 is relating to the maximum current. However, the ST-LINK is equipped with it’s own LD3985 voltage regulator, on the schematic denoted as U4:

Hence, after removing the D2 diode from the board the ST-LINK won’t be powered when the board is supplied from an external source over the pin 4 of the CN4 connector. But still can be used when powered from U5V over the USB VBUS.

Best regards,


Hello Zoltan

Thank you for your reply, and detailed response

Sadly JANs first response was unlike yours!, and we got off to a bad start with his initial reply :frowning:

Credit to Jan for giving up he’s free time, lets all say thank you Jan :slight_smile: as I respect anyone helping in their free time.

In relation to the original post,

I have used extensively various 144 / 64 pin processor nucleo boards in the past with my segger debugger and was planning to start a new project using the simple 32 pin processor nucleo board.

The larger boards let you disconnect and even better snap off the stlink debugger so you can throw away the unwanted clutter (stlink)

but sadly you can not with the smaller nucleo 32 boards ? there are hard wired tracks from the stlink arm to the user ARM

though I fully understand what you say about killing the power to the stlink, though from a design point of view this is not ideal and there may be unwanted loading on the pins now being used by the segger.
For the sake of having some isolation pads to allow total disconnect of the onboard stlink, how hard could this be ?

This was the point I was making, though I fully take onboard No one is perfect, … I was having a bad day and wasted lots of time only to find out these design flaws.

The point I was making is the larger nucleo boards allow total isolation of the stlink, why could not the smaller board too ?

But thank you very much for you input and professional reply, you have kindly restored my faith in this website and the support and time you have given me.

Thank You

Regards John

Why does this site keep hiding content???

This is all constructive info in helping others not to waste time using small nucleo boards
if they want to use there 3rd party debuggers

Why hide the content of these posts, everything stated is highly accurate ?