What is required to utilize USART3 on the STMod+ Fan-Out Expansion Board when using the STM32L4P5G-DK Discovery Kit?

[Zak]

I start a new project with the following steps:

1. I create a new STM32 Project
2. I select STM32L4P5G-DK from the Board Selector Menu
3. I initialize the board with it's default configuration

I have successfully configured the I2C4 and USART2 peripherals on the STMod+ Fan-Out Expansion Board, and they are working as expected.

However, I am having difficulty when I attempt to enable USART3 (available on the expansion board) for use with my project. I resolve the conflicts (warnings) and get the "green checkmark" (as I did with the other peripherals), but when I look at the pins on my oscilloscope, there is no activity. What gives?

As far as hardware configuration goes, I'm already using the I2C4 bus on the STMod+ Fan-Out Expansion Board, so I'm assuming the STMod+ (CN1) connector is enabled. Is this a good assumption, or is there a jumper on the board that needs to be configured to "fully activate" the STMod+ connector?

As far as I can see, all signs are go. I need help determining how my firmware or hardware is misconfigured.

Here is the Device Configuration Tool view:

Pinout from the User Manual:

[TDK]

Did you close the necessary solder bridges?

Also seems like you still have SPI1 in use, which will fight for the same pins as USART3, unless you've changed them.

[Zak]

I was unaware of the solder bridges, so I'm sure that is a problem. Where are they located on the STM32L4P5G-DK? Also, what documentation are you referencing? I would like to learn how I could have found that on my own.

Finally, why doesn't the STMCubeIDE report the pin conflict? Why am I receiving the "green check mark", when there is such an obvious configuration issue?

I'll hunt for the solder bridges, but if you're up for it, I would still appreciate a pointer. In the meanwhile, I've attached my NEW pin configuration, in case you can see any other obvious problems.

[TDK]

> Where are they located on the STM32L4P5G-DK?

The bridge should be labeled on the board. Might take a minute but just looking for it is probably the easiest way. If you get really desperate, you can download the board manufacturing files and Ctrl+F for it.

 

> Also, what documentation are you referencing?

The schematic and other stuff are available under documentation on the product page. There is also a user manual, although it didn’t mention the solder bridges at all as far as I could see.

https://www.st.com/en/evaluation-tools/stm32l4p5g-dk.html#documentation

> Finally, why doesn't the STMCubeIDE report the pin conflict?

CubeMX has no idea the pins are tied together (via solder bridges) on the board, so it doesn’t know there’s a problem to report.