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stm32-rs / stm32f3xx-hal

A Rust embedded-hal HAL for all MCUs in the STM32 F3 family
https://crates.io/crates/stm32f3xx-hal
Apache License 2.0
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Thoughts on clock config #157

Open David-OConnor opened 3 years ago

David-OConnor commented 3 years ago

It seems like the current system fails silently, and gives the user too many degrees of freedom. Eg the illusion you can set whatever speeds you want. I think the STM32Cube IDE visual clock config is a good guide for what configs are valid.

Suggestion: Instead of setting speeds, set the various scalers. This alone reduces the degrees of freedom. Have a helper method to show what speeds these output. Calculate the speeds, and validate before setting. This deals with errors in 2 ways: Prevents requesting speeds that can't be set using the scalers and 2: Fails explicitly if the resulting speeds are out of range.

David-OConnor commented 3 years ago

Closing in favor of https://github.com/stm32-rs/stm32f3xx-hal/pull/159

Sh3Rm4n commented 3 years ago

Also some ideas came up in https://github.com/stm32-rs/stm32f3xx-hal/pull/156.

David-OConnor commented 3 years ago

I just noticed that the L0 hal implementation is very similar to the clocks module in my fork. Its base struct holds prescaler values. Its primary API is to use a default. It uses enums for the various scalers, and has functions to show you the resulting speeds.

Sh3Rm4n commented 3 years ago

This is an issue, I still want to tackle, but had no time as of now. I summarized my preferences how to implement a more robust and flexible clock configuration in https://github.com/stm32-rs/stm32f3xx-hal/pull/156#pullrequestreview-514497743