Using NUCLEO-U031R8 STLINK VCP on external target

[yichen15922]

Hello!

I am using the onboard STLINK on the NUCLEO-U031R8 to program a STM32U0 on a custom PCB. I use the SWD interface connected over jumper wires and programming works fine. I would like to enable printf for debug purposes, and since SWV is not available for this series, I am trying to connect USART2 from my PCB to the STLINK using fly wires. However, I can't seem to find where the TX and RX pins are exposed on the STLINK. The jumpers and CN3 mentioned in section 6.8 of UM1724 also don't match up. On further inspection, it seems that some Nucleo boards have the TX and RX pins exposed as a header, but my particular one does not. Is there a way for me to use VCP this way with this Nucleo board? 

Thank you in advance! 

[Pavel A.]

Do yourself a favor, get ST-LINK v3 MINIE.  Be happy.

[TDK · Accepted solution]

https://www.st.com/resource/en/schematic_pack/mb1932-u031r8-b01-schematic.pdf

They're not exposed at a header. If you have tools/skills to remove the resistor and solder a wire in its place, you could use them. This is going to be out of reach for most hobby setups.

As @Pavel A. suggests, you can use a 0.05" pitch 14 pin header to interface with a standard programmer and route out the VCP signals that way.

[yichen15922]

Thank you all! I was just trying to make sure I didn’t miss anything obvious. I stumbled on an old STLINK V3 lying around the lab so I’m using that now.