I am currently trying to connect the ST-LINK/V2 to my custom board which is using a STM32F446RC. I am able to detect the ST-LINK using both the STM32CubeIDE or the STM32 ST-LINK utility, however this is only displaying the serial number. but it is failing to detect the target (MCU).

Additionally, here's some more information I have gathered while trying to debug it:

  • BOOT0 is set to low (hardwired to GND)
  • BOOT1 is set to low (hardwired to GND)
  • VCAP voltage is reading at 1.14 V
  • NRST voltage is high
  • VCC is stable at 3.3 V
  • ST-LINK is receiving a stable 3.3 V
  • VDDA is stable at 3.3 V
  • \$\begingroup\$ If you have a fake ST-LINK/V2 then it won't work. \$\endgroup\$ Sep 21, 2021 at 6:07
  • \$\begingroup\$ I've never had any problems with ST-LINK clones. It's unlikely that this is the problem. \$\endgroup\$
    – Codo
    Sep 21, 2021 at 6:12
  • \$\begingroup\$ You should post a schematics of your board in order to get an answer. \$\endgroup\$ Sep 21, 2021 at 7:03
  • \$\begingroup\$ Fake STM maybe? I had issue with my Chinese stm,could not upload via STlink, I had to follow a tutorial and do some changes to some files. \$\endgroup\$ Sep 21, 2021 at 8:20
  • \$\begingroup\$ Probe SWD and SWCLK, does the chip respons to anything? If not, rdp level2 is active or it's a dud. \$\endgroup\$
    – Jeroen3
    Sep 21, 2021 at 9:35

2 Answers 2


Signal integrity...

I had a similar issue years ago. The schematics was fine, the programmer was working with other boards. etc.

I had the idea to probe the SWD signal. It was a mess.

The root cause? I used 10cm long individual wires to bond the STlink to my programming socket, not ideal for high-speed signal transport.

Solution: I configured my STLink SWD to program using a much lower clock frequency. And BAM It instantly worked like a charm.

If you can't probe the SWD data and clock lines at the chip pins, just try to reduce the programming clock speed to a ridiculously slow speed and check if that works.

  • \$\begingroup\$ Arg ! An old post bumped at the top..... I haven't seen. But the answer it still valid for others.... \$\endgroup\$
    – Blup1980
    Nov 8, 2023 at 7:51

Try "erasing the chip" using "st-link utility" app while pulling down the NRST pin with a 500 ohm resistor. If this doesn't work it is very probable that you have hardware issue(sth is broken!).


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