docs: Add a new variant (board) and "Generic System Clock configuration"

[thernstig]

I had a hard time understanding https://github.com/stm32duino/Arduino_Core_STM32/wiki/Add-a-new-variant-%28board%29#3---generic-system-clock-configuration.

I am quoting the parts I found hard and what I felt was missing/strange:

Go to Pinout tab, enable the desired peripherals which require specific clock configuration (not needed for peripherals clocked by HCLKx, or APBx clock): SDIO, USB, ... In this example only USB needs to be enabled as other peripherals default clock are correct by default.

What is "desired peripherals" here? How would I know what to enable?

Set PLL Source Mux to HSI.

There is no PLL Source Mux for the MCU I added in #2556. The sentence is written like it is something that should exist, but it does not seem true for all MCUs.

[thernstig]

In addition, this part:

6 - Restart
Restart Arduino IDE and try one of the new entry with the CheckVariant example.

It mentions nothing on how to do this on that above page. Should there have been a link to somewhere on how to load the new board into Arduino to test it?

[fpistm]

The board should appears in the menu you add it that's all. Select it and voilà.

[thernstig]

@fpistm I am talking about an unreleased version of Arduino_Core_STM32. Then the new board does not immediately show up in the JSON file does it?

[fpistm]

Yes. I need to perform a release.
But if you use the git repository in the Arduino package you will see it.

[thernstig]

@fpistm I think this part:

But if you use the git repository in the Arduino package you will see it.

Is not explained from https://github.com/stm32duino/Arduino_Core_STM32/wiki/Add-a-new-variant-%28board%29#6---restart.

How would one know how to do this? I just started with both Arduino and STM32, so consider it from a point from someone who never used these tools before (even though understanding the basics).

[fpistm]

It is explained here: https://github.com/stm32duino/Arduino_Core_STM32/wiki/Using-git-repository

Feel free to propose update, it is a community project.

[thernstig]

I would propose a lot more if I knew the answers 😆

[thernstig]

Wrote #2559 as a separate issue.

The two core issues of this topic are still valid. I do not know how to update those as I have no idea what those parts in reality mean.