No STM32 target found

jwtuttle · ‎2026-04-20

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

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

Andrew Neil · ‎2026-04-21

@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.

View solution in original post

Peter BENSCH · ‎2026-04-21

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

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mƎALLEm · ‎2026-04-21

Hello,

Try to connect with "Power Down" mode:

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

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Andrew Neil · ‎2026-04-21

@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.

jwtuttle · ‎2026-04-21

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 · ‎2026-04-21

@jwtuttle wrote:
Hopefully our ST-Links are legit. We bought them from Digi-key.

Even DigiKey do sell clones:

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.

Andrew Neil · ‎2026-04-21

@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.