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Use nucleo-64 ST-Link debugger for another MCU

vernture
Visitor

‎2025-09-12 12:03 AM

Removed the ST-Link plastic jumpers and all four pins are free now - as shown on the blue rectangle. As well as, the yellow rectangle shows the 6 pins of CN4 on one column.

photo_2025-09-12_01-11-34.jpg

It seems that pins 1 and 3 are 3.3 V and GND respectively based on the use manual (https://www.st.com/resource/en/user_manual/um1724-stm32-nucleo64-boards-mb1136-stmicroelectronics.pdf) 

Capture3.PNG

but when I check those two pins using a multimeter I get no voltage! Any idea where is the issue?

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4 REPLIES 4
mfgkw
Associate III

‎2025-09-12 12:51 AM

VDD is not driven by the ST-Link, but has to be connected to power of the MCU to be flashed/debugged.

This might be 3.3V or another voltage, depending on your board.

ST-Link reads this voltage.

 

Only if the jumpers are NOT removed then the ST-Link is connected to your MCU on the NUCLEO and VDD is delivered from there (one of the removed jumpers routes VDD).

vernture
Visitor
In response to mfgkw

‎2025-09-12 1:57 AM - edited ‎2025-09-12 2:01 AM

@mfgkw wrote:

Only if the jumpers are NOT removed then the ST-Link is connected to your MCU on the NUCLEO and VDD is delivered from there (one of the removed jumpers routes VDD).

That's odd to me because the USB power is connected to CN1 of ST-Link part and pins 1 and 3 (from the top) give zero voltage even if I put those jumpers back.

My purpose is to make the connections below to use the Nucleo's ST-Link debugger for a code that's going to program the Blue Pill.  

Nucleo ST-Link   |   Blue Pill
--------------------------------------------
VDD_TARGET  =>   3.3V
SWCLK             =>   PA14
GND                 =>    GND      
SWDIO             =>    PA13
NRST               =>     NRST

When I connect these, the blue pill's power LED doesn't turn on so it doesn't receive power from the ST-Link. 

My board, as shown from the image in the first post, is Nucleo-64 STM32F411RE. 

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Andrew Neil
Super User
In response to vernture

‎2025-09-12 2:24 AM - edited ‎2025-09-12 2:29 AM

As @mfgkw said, and as shown in the table you quoted, pin 1 is VDD from the target - it does not supply power to the target:

AndrewNeil_0-1757668763408.png

To be really sure that the ST-Link is fully disconnected from the STM32F411RE on the Nucleo board, you can break-off the ST-Link part:

AndrewNeil_1-1757668983963.png

Picture credit: @MM..1 via https://community.st.com/t5/stm32-mcus-products/3-3v-power-supply-for-nucleof103/m-p/657826/highlight/true#M240024

 

PS:

@vernture wrote:

That's odd to me because the USB power is connected to CN1 of ST-Link part . 

Not directly:

AndrewNeil_2-1757669203474.png

AndrewNeil_3-1757669253175.png

 

@vernture wrote:

the blue pill's power LED doesn't turn on so it doesn't receive power from the ST-Link. 

That is the expected behaviour.

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.
vernture
Visitor
In response to Andrew Neil

‎2025-09-12 2:51 AM

Thank you, but I'm still rather confused what to do.
I don't want to break off the ST-Link part (because I have projects working with the Nucelo board); I just need to disconnect (perhaps using the jumpers) the ST-Link from the Nucelo part and use the St-Link part for the Blue Pill as said earlier. So for that:

1- What jumpers should I remove? Are the two ones of CN2 enough?

2- What pins of the ST-Link should I connect to the Blue Pill's pins? Are they still those 6 pins of CN4!?  

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