CN5 SWD connection with external ST-Link v2 does not work on STM32L552ZET6Q Nucleo-144

[mattcylee]

Embedded ST-Link via CN1 USB is working fine. I followed the direction as below when external ST-Link v2 was tried on STM32L552ZET6Q Nucleo-144. The error message "No Target" was displayed on STM32CubeIDE with external ST-Link. Could you provide me with any advice?

[TDK]

A few questions:

• Why use an external programmer instead of the on-board one?
• Is the board powered? How?
• Is your programmer a genuine ST device? I don't particularly care but knock-offs tend not to work well with STM32CubeIDE.
• Try connecting with STM32CubeProgrammer. Does it report a target voltage? Does it connect? Show screenshots if you get errors.

[mattcylee]

1. My H/W board with STM32L5 is under design and will use external ST-Link v2 for programming and debugging. That's why I tried to validate external ST-Link connection.

2. USB C at CN15 is used as board power supply. pin 7 and 8 is on JP6 for external power. 

3. Yes. I use genuine ST device

4. Please check the screen capture as below. Target board voltage is pretty low as 0.23 (Probably shall be around 3.3v).  

USB C is not enough external power?

[TDK]

0.23 V is not enough voltage for the device to run.

How is the device powered? The programmer does not provide power. The VCC pin is an input to the programmer.

[TDK]

There are a number of ways to power the board. You need to have one of those present. See the user manual for details. CN15 should work.

[mattcylee]

pin #1 on CN5 is connected to pin #1 on 20 pin connector of ST Link v2. L552E-Q board is powered from USB C (CN13). Board connection with ST link v2 is captured as below.

[mattcylee]

After CN5 pin1 is connected to 3.3V on CN8, target voltage is 3.24v. However, still NO STM32 target found.

[TDK · Accepted solution]

CN5 is no longer connected to SWD on the target chip since you've disconnected CN4. It's connected to the st-link chip.

https://www.st.com/resource/en/schematic_pack/mb1361-l552zeq-c02_schematic.pdf

If SWDIO/SWCLK (PA13/PA14) is exposed elsewhere that would be best. It's on some headers. If you connect CN4 it may not like another programmer trying to drive those lines.

[mattcylee]

After two jumpers are back to CN4, external ST-link v2 starts working. Thanks for your support.