my stm32f4 cannot connect to stlink normally

[Glowing_Brick]

I am facing an issue with my custom-made STM32F4x minimum system board. I am experiencing unstable connections with the STLink. I am using an AMS1117 for power supply, and I have found that when the STLink supplies power at 5V to the AMS1117, it cannot connect properly. Similarly, when I directly connect the 3.3V output to VDD, it still does not connect properly. Although all the voltage readings at various points are correct (VDD is 3.3V, and VCAP is 1.25V), I cannot establish a connection with the STLink. However, the STM32 is booting up normally, and the LED flashing program I previously burned is running. Additionally, I can connect and burn using the serial port, but only the STLink connection fails. I have also tested reducing the SWD frequency to 5kHz, but it still cannot connect. The logic analyzer shows some errors and no replies in the SWD response, but there are a few ‘OK’ responses as well. Occasionally, I find that I can connect properly, but it seems to happen randomly without any changes on my part. However, when I connect the 3.3V to the AMS1117 (with all other connections remaining the same), the output to VDD is approximately 2.3V, and the STLink can connect properly. After thorough checking, I still couldn’t identify the issue.

[STOne-32]

Dear @Glowing_Brick ,

Welcome in STCommunity , is that possible to have a picture of the top marking of your device ? To check is the MCU is a genuine one . We have seen similar posts and behavior and at the end the MCU was not from ST and ST-link detect it .

Hope it helps ,

STOne-32

[Glowing_Brick]

Of course. Thank you for your kindness

The SWD id of it is 0x2ba01477,Seems consistent with the manual

[STOne-32]

Hi @Glowing_Brick ,

Thank you .  

No particular visible issue but I still have some doubts - how you flashed a code ? Is that possible to Program via ST-Link and STM32CubeProgrammer and read the UniqueID etc ?  Or may be also ST-Link issue if possible to have a picture as well . 

 Ciao

STOne-32

[Glowing_Brick]

Thank you for your help :)

I directly flashes the code at 2.3V.... The UniqueID read from 0x1FFF 7A10  is: 

0x540057 0x31385113 0x31363930 

I’ve previously used this ST-Link for debugging an STM32F103 without any problems. here's a picture of the ST-Link after removing its case. 

Could this issue potentially be related to the circuit design? Since this core board is homemade and this is its first test, I don't know if there might be a critical design flaw ...

[STOne-32 · Accepted solution]

Dear @Glowing_Brick ,

Indeed this is not our STLink and not produced by ST , this is a clone most probably. So issue is coming from there .

Similar Discussion here :

https://community.st.com/t5/stm32-mcus-products/stm32f405rgt6-custom-board-not-detected-on-stm32programmer/td-p/691766

STOne-32