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Soundhariyan
Associate
October 28, 2026
Question

Technical Support Request – ST-LINK Debugger Fails to Flash code STM32H750VBT6 Target

 

Dear STMicroelectronics Technical Support Team,

We are experiencing a target detection and firmware programming issue with an ST-LINK debugger manufactured in Vietnam and purchased from DigiKey.

We are using the STM32H750VBT6 microcontroller on our custom development board and programming it through STM32CubeIDE and STM32CubeProgrammer.

We have tested two ST-LINK debuggers on the same development board. One debugger, manufactured in China, works correctly, while the other, manufactured in Vietnam, fails to detect the target microcontroller.

1. Working ST-LINK Debugger (Made in China)

When the debugger is powered without connecting it to the target board:

  • 3.3 V pin voltage: 3.3 V

  • SWDIO pin voltage: 3.1 V

After connecting it to our STM32H750VBT6 development board:

  • Development board supply voltage: 3.3 V

  • ST-LINK 3.3 V pin voltage: 3.3 V

  • SWDIO pin voltage: 3.18 V

  • STM32CubeProgrammer detects the ST-LINK successfully.

  • Target voltage reported: 3.13 V

  • Target MCU is detected successfully.

  • Firmware programming through STM32CubeIDE works correctly.

2. Non-working ST-LINK Debugger (Made in Vietnam, Purchased from DigiKey)

When the debugger is powered without connecting it to the target board:

  • 3.3 V pin voltage: 3.277 V

  • SWDIO pin voltage: 0.0 V

After connecting it to our STM32H750VBT6 development board:

  • Development board supply voltage: 3.058 V

  • ST-LINK 3.3 V pin voltage: 3.054 V

  • SWDIO pin voltage: 2.164 V

  • STM32CubeProgrammer detects the ST-LINK successfully.

  • Target voltage reported: 1.01 V

  • Target MCU is not detected.

  • Firmware programming fails with the error: "Target no device found."

3. Our Concern

Both debuggers have been tested with the same STM32H750VBT6 development board. The working debugger can connect to the target and program firmware successfully, whereas the DigiKey-purchased debugger is unable to establish target communication.

We have also observed a significant difference in the target voltage reported by STM32CubeProgrammer, despite measuring approximately 3.05 V on the target board.

4. Request for Technical Support

We kindly request your assistance in identifying the possible cause of this issue.

Specifically, please clarify:

  1. Why does the non-working ST-LINK report a target voltage of only 1.01 V when the development board voltage is approximately 3.05 V?

  2. Is a 0 V reading on the unconnected SWDIO pin normal for this ST-LINK model?

  3. Could this indicate a problem with the target voltage sensing circuit or SWD interface?

  4. Are there any additional diagnostic procedures or firmware updates recommended to verify the debugger?

  5. If the debugger is confirmed to be defective, please advise on the appropriate replacement or warranty procedure through DigiKey.

We can provide photographs of both debuggers, STM32CubeProgrammer logs, voltage measurements, and purchase details for further investigation.

We look forward to your technical guidance and assistance in resolving this issue.

Thank you.

Best regards,
E&E Team
Vertex Research Center Private Limited ,palladam,Tamilnadu,India

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