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jwtuttle
Associate II
April 20, 2026
Solved

No STM32 target found

I have been programming my STM32H743 custom board for over a year.  Suddenly I'm getting the error message Error: No STM32 target found...

jwtuttle_0-1776721104744.png

I have tried changing the ST-Link itself but get the same error message.

Andrew Neil
Andrew NeilBest answer
Super User
April 21, 2026
@jwtuttle wrote:

what is the sequence the the ST-Link performs to determine that a STM32H743 is present?

It must do the standard SWD connection sequence:

https://developer.arm.com/documentation/ihi0031/a/The-Serial-Wire-Debug-Port--SW-DP-/Protocol-description/Connection-and-line-reset-sequence

It'll also query things like the device ID to find what part it is ...

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.
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6 replies

Peter BENSCH
Peter BENSCH
ST Technical Moderator
April 21, 2026

If it is an ST-LINK/V2, please include photos of the front and back so that it can be ruled out that it is one of the clones being referred to here.

Regards
/Peter

In order to give better visibility on the answered topics, please click on Accept as Solution on the reply which solved your issue or answered your question.
    mƎALLEm
    mƎALLEm
    ST Technical Moderator
    April 21, 2026

    Hello,

    Try to connect with "Power Down" mode:

    mALLEm_0-1776783657941.png

    Otherwise, what happened in between (working to not working)?

     

    To give better visibility on the answered topics, please click "Best answer" on the reply which solved your issue or answered your question.
      Andrew Neil
      Andrew Neil
      Super User
      April 21, 2026
      @jwtuttle wrote:

      Suddenly I'm getting the error 

      So what did you change ?

      After a year, also check for broken wires, loose connectors, etc

       

      How to solve connection errors when connecting and programming the STM32 target board.

      How to solve debugger connection issues

       

       

      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.
      jwtuttleAuthor
      Associate II
      April 21, 2026

      Hopefully our ST-Links are legit.  We bought them from Digi-key.

      What changed: It appears that the interface board that we use to go from the 20 pin 0.1" spacing cable to the 0.05" 10 pin cable has worn out.  So that's the source of my problems.

      But for debugging purposes in the future, what is the sequence the the ST-Link performs to determine that a STM32H743 is present?

      Obviously, the ST-Link saw the voltage since it displayed the correct value.  But I did not see any of the signal lines change.  As in, NRST didn't go Low, SWDIO and SWCLK didn't toggle.  I assume in a working system these lines should toggle

       

        Andrew Neil
        Andrew Neil
        Super User
        April 21, 2026
        @jwtuttle wrote:

        Hopefully our ST-Links are legit.  We bought them from Digi-key.

        Even DigiKey do sell clones:

        AndrewNeil_0-1776788987505.png

        Hence the request to see photos of what you're actually using.

         

        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.
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