Nucleo-64 ST-LINK Fails with External PCB (But Works with ST-LINK V2)

[Manowi25]

Hello,

I previously used ST-LINK V2, which worked fine, but due to its lack of a Virtual COM Port (VCP), I recently purchased a NUCLEO-64 (STM32F030R8 EVAL BRD) to program my own PCB using its ST-LINK.

The Nucleo board itself works fine, but when I try to use its ST-LINK to program my own PCB (using STM32G030F6P6TR), I encounter issues despite following the manual:

What I Have Done:

• Removed CN2 jumpers to enable external debugging.
• Wired ST-LINK (CN4) to my PCB:
  • VDD_TARGET → My PCB’s 3.3V
  • GND → Shared with Nucleo
  • SWCLK → My PCB's SWCLK
  • SWDIO → My PCB's SWDIO
• Powered my PCB with an external 3.3V source.

What Happens:

• Without external power: STM32CubeProgrammer does not connect.
• With external power: CubeProgrammer connects but disconnects after ~10 seconds, then crashes.

I have been troubleshooting this for days but found very few resources on using a Nucleo board's ST-LINK for external programming.

As mentioned, the Nucleo board itself works fine, and my PCB works with ST-LINK V2, but not with this Nucleo ST-LINK.

Do you have any insights on why this might be happening?

[TDK]

> Without external power: STM32CubeProgrammer does not connect.

This is expected as CN4 does not provide power.

> With external power: CubeProgrammer connects but disconnects after ~10 seconds, then crashes.

Any error messages? Does lowering the speed help? Updated ST-Link firmware?

Ground loops could always cause an issue. Can you power it from the nucleo board and see if that changes things?

[Manowi25]

Hello,

Thank you for your comment.

Yeah, I tried all kinds of things, including updating the firmware...

Strangely, I connected the Nucleo board to another STM32 dev board, and it worked. Then, I reconnected the Nucleo back to my custom PCB, and it worked halfway—it stopped crashing but still couldn't be programmed. After that, I connected my second custom PCB (which is exactly the same as the original one I was working on), and it worked. Then, when I reconnected my original PCB, it started working as well...

I really don’t know what’s happening, but now I can program. However, USART still doesn’t work. Maybe I need to snap the ST-Link part to use USART on my custom PCB, perhaps...

[TDK]

Probably a bad solder joint somewhere or other manufacturing issue. Could also be a design issue.

[STOne-32]

Dear @Manowi25 ,

Can you share your target MCU part and good resolution photo  soldered on the PCB ? 
Ciao

STOne-32