UART Serial Monitor using VS Code, Linux, and ST-Link

[hdferguson3]

I have an older STM32 Nucleo-F746ZG and I want to try and send some serial over the ST-Link. I am in Ubuntu with VS Code. I have successfully built the project and it appears to be running in debug mode. However when I try to connect and read the serial output via Screen, Putty or even the Serial Monitor extension nothing is showing up on the serial port. I have found the ST-Link is at /dev/ttyACM0 and I have added my user to the dialout group, but nothing shows up.

I am using UART2 in Asynchronous mode, added interrupt and using VS Code in debug mode. I suspect that this is OS related, but wanted to know if anyone had any suggestions on where to look.

I have done other projects with STM32-Nucleo and VS Code so I believe this is a simple error on my part related to the ST-Link usb in Linux.

Doug

[Andrew Neil · Accepted solution]

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@hdferguson3 wrote:

I am using UART2 

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Is that USART the one connected to the ST-Link ?

eg, https://community.st.com/t5/stm32-mcus-products/uart-doesn-t-work/m-p/759888/highlight/true#M270155

[hdferguson3]

How can I determine that?

[Andrew Neil]

From the board's User Manual and/or Schematics - as illustrated in the linked post/thread

[hdferguson3]

Oops, let me swap to USART3 and try this again!!! I'll report back.

[AScha.3]

see circuit :

https://www.st.com/resource/en/schematic_pack/nucleo_144pins_sch.zip

[hdferguson3]

Boom! That was it. I knew I had overlooked something simple. I followed a tutorial and looking back that didn't overly make clear which USART they picked an why. So, make sure you know which USART to use and why. 

Thanks!

[Andrew Neil]

You said it's, "an older STM32 Nucleo-F746ZG" - does that mean it's previously been used by you and/or others?

If yes (especially if others have been using it), you'll need to check those solder bridges (SB4, SB5, SB6, SB7)

[Andrew Neil]

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@hdferguson3 wrote:

So, make sure you know which USART to use and why. 

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Indeed - it seems to be a common omission!

Which tutorial did you follow? Maybe feed back to the author ...

[hdferguson3]

The board has always been mine, I just haven't used it in awhile.

The tutorial was a YouTube video I am embarrassed to say.