2025-09-28 6:59 AM
I made a custom 4 layer board using STM32H735VGT6 (schematic and PCB layout attached).
I am trying to upload code into the MCU flash via ST-LINK V2, but it fails to connect.
At first, I realized that I had not connected VDDLDO to 3.3V, which I thought was the problem. However, even after connecting it to 3.3V, I still cannot upload code.
Error from CubeIDE:
STMicroelectronics ST-LINK GDB server. Version 7.11.0
Copyright (c) 2025, STMicroelectronics. All rights reserved.
Starting server with the following options:
Persistent Mode : Disabled
Logging Level : 1
Listen Port Number : 61234
Status Refresh Delay : 15s
Verbose Mode : Disabled
SWD Debug : Enabled
InitWhile : Enabled
Target no device found
Error in initializing ST-LINK device.
Reason: No device found on target.
I also tried the “hold reset while clicking connect, then release” method, but it still fails.
This is a newly soldered MCU. I have not uploaded any code to it yet. I also tried switching BOOT0 from low to high to enter system bootloader and erase flash via USART1 (PA9/PA10), but failed as well.
Power connections:
I have 2 2.2µF capacitors connected to 2 of the 3 VCAP pins, and for the last one I connected it to one of the VCAP pin (as per datasheet).
The measured voltage on VCAP pins is ~0.99–1.0V instead of 1.2V. I’m not sure if this is indicates an issue.
At this point, I’m unsure whether the problem is hardware-related (power/VCAP), ST-LINK wiring, or boot issue. Any advice on what I might be missing and how to recover would be appreciated.
Solved! Go to Solution.
2025-09-28 7:51 AM
Welcome @Dn1te, to the community!
I suspect that ST-LINK/V2 is the cause of your problem. Please post photos of your ST-LINK/V2, including the back if it has a plastic casing.
Regards
/Peter
2025-09-28 7:51 AM
Welcome @Dn1te, to the community!
I suspect that ST-LINK/V2 is the cause of your problem. Please post photos of your ST-LINK/V2, including the back if it has a plastic casing.
Regards
/Peter
2025-09-28 9:15 PM - edited 2025-09-28 10:51 PM
Thank you for your help. The pinout of the ST-LINK I use is exactly the same as the one shown in the first picture below. I also tried using another ST-LINK (with the pinout in the second image), but that failed as well.
At this point, I suspect the issue might be related to the power supply on my board.
EDIT: I changed to another ST-LINK and was able to perform a flash erase successfully. Now I can connect to ST-LINK constantly. Thanks you Peter for your help
2025-09-28 11:00 PM
I would check the hardware.
The voltage at the supply pins should be in range, and the current consumption as well. I'm not sure if the ST-Link can supply the target, I had trouble with that occasionally. Better try an external supply.
I cannot really comment on the ST-Link V2 issue. I know there are some non-functional fakes around.
You could try the onboard ST-Link from another ST board, or another debug pod like a JLink. Or try Segger's JLink firmware for ST-Links, which is reversible.
2025-09-29 12:31 AM
If you use such a fake ST-LINK/V2 or clones in these tin cans, you cannot expect them to be supported by the tools from STMicroelectronics. Get yourself a genuine ST-LINK/V2 or, as @Ozone mentioned, use an ST-LINK from a NUCLEO board, and you will have no problems.
However, an ST-LINK/V2 does not supply power to a target, but only checks its voltage against the setpoint. You must therefore always supply the target separately.
Regards
/Peter