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I'm new to PCB design and I'm currently trying to debug an issue with a design that uses an STM32U545NEYxQ. The problem is that the board cannot communicate with the STLink/V2.

When I try to connect using STM32CubeProgrammer, I tested all STLink configurations, but always receive the error:

"Error: No STM32 target found! If your product embeds Debug Authentication, ..."

And in STM32CubeIDE, the message is:

"Error in initializing ST-LINK device. Reason: No device found on target."

I'm confident that the STLink is working correctly, as I have tested it with other boards successfully.

I've also checked other forum threads for common beginner mistakes in hardware design, but I haven’t found any of those issues present in this design.

The board is a 4-layer design:

  • One layer for VCC (3.3V)

  • One GND plane

  • Two signal layers (top and bottom)

I've attached images of all four layers along with the schematic for reference.

enter image description here enter image description here enter image description here enter image description here enter image description here

I also attempted to debug the SWD communication signals. When the STLink tries to initiate communication with the board:

  • SWCLK (blue trace) seems to toggle normally.

  • SWIO (yellow trace) doesn’t appear to reach a low logic level.

I'm not sure if this is the root cause of the problem. If it is, what could be preventing SWIO from going low, and how can I fix it? enter image description here

Any insights would be appreciated!

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1 Answer 1

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The schematic violates multiple points how to power the MCU.

The main point is that your schematic shorts the core output voltage to ground, so the MCU core is unpowered and the LDO is likely overheating due to output being shorted. The capacitors for LDO output are missing.

The schematic even grounds the SMPS input and output.

Please refer to data sheet how to make a new PCB so MCU works.

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  • \$\begingroup\$ Indeed, in particular, the first few sections of the Electrical Specifications in ST's MCU datasheets show a power supply connection scheme for e.g. LDO or SMPS operation. They will show how to connect the analog, I/O & core supply rails, and what to do with the SMPS pins. \$\endgroup\$ Commented May 19 at 21:18

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