Target No Device Found: SWDIO (PA13) at 0V on STM32L073CZT Custom Board

[VENKATESH2123]

Hello STM32 Community,

I am facing a persistent "Target no device found" error when trying to program an STM32L073CZT3 custom board using a Nucleo-L073RZ as an external ST-LINK (CN2 jumpers removed).

Hardware Setup:

• MCU: STM32L073CZT3 (custom PCB)

• Debugger: ST-LINK V2-1 (Nucleo-64)

• Connection: 5-wire SWD (SWDIO, SWCLK, GND, NRST, VDD_Sensing)

• Power: External SMPS providing 3.3V (Common Ground established between SMPS and ST-LINK).

The Issue: While the ST-LINK pins show correct voltages when floating, the SWDIO (PA13) pin drops to 0V the moment it is connected to the target board.

• Pin 1 (VDD Sense): 3.3V

• Pin 2 (SWCLK): 3.29V

• Pin 4 (SWDIO):  (Measured 2.9V on ST-LINK side connection)

• Pin 5 (NRST): 3.3V

Troubleshooting performed:

1. Verified continuity; no physical shorts found between PA13 and GND.

2. Attempted "Connect Under Reset" and "Hardware Reset" at 480 kHz.

3. Schematic Check: I have a 10uF capacitor (C17) on the NRST line—could this be preventing the debugger from catching the reset state?

4. Verified that the ST-LINK and the software setup work perfectly on a standard Nucleo-L073RZ board.

I have attached my schematic and a photo of the physical wiring. Does the 0V on SWDIO suggest a software-locked pin or a hardware fault within the MCU?

STMicroelectronics ST-LINK GDB server. Version 7.5.0

Copyright (c) 2023, 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.

Best regards, VenkatesH

[mƎALLEm]

Hello @VENKATESH2123 and welcome to the ST community,

Please review this knowledge base article: How to program an STM32 using the on-board ST-LINK/V2-1 of the NUCLEO-WB55RG

Also refer to this post: How to use the standalone ST-LINK capability of my nucleo after I cut the PCB?

 

 

[VENKATESH2123]

Is there any mistake in our schematic

[mƎALLEm]

Please refer to the hardware getting started application note AN4467, especially the figure 15:

And check again this knowledge base article: How to program an STM32 using the on-board ST-LINK/V2-1 of the NUCLEO-WB55RG

Check also your hardware especially solder joints issues.

 

[VENKATESH2123]

 

• It is still not working, and I have checked all the connections.
• Is there any mistake in my schematic?
• Any issue in power design (VDD / VDDA)?
• Any problem with SWD or NRST connections?
•  

 

[Mike_ST]

Hello,

Hard to tell with not so detailed pictures.

Check for bridged pins on the STM32.

Check for rotated chip.

On your implementation of the debug connector, I maybe see that you've switched SWCK and SWIO compared to our implementation on the nucleo, please make sure this is not the problem.