Working HAL for the XOSC

[Nic0w]

Hi,

This is a full, working implementation of a CrystalOscillator that allows use of the XOSC.
Typestate programming is used to transition between the different stages : Disabled > Initialized > Stable > Disabling, Dormant.

I've tested the code on my Pi Pico up to the first 3 stages (ie up to Stable) and confirmed with the Frequency Counter that the XOSC's frequency is indeed 12MHz at that point.

To be noted that the code is based on hardware_xosc/xosc.c from the official pico-sdk.

I also want to point out that I'm a novice in Rust and that this is my first ever contribution to a Rust crate, so don't hesitate to point out things that I could have done better.

Regards,

[tdittr]

Hi,

thanks for taking up the work on the Oscillator. I started work on this previously, but I think you picked up from there anyway?

Overall this PR looks really good. I would just change a few minor details and maybe not yet expose the Dormant mode.

[Nic0w]

Hi,

thanks for taking up the work on the Oscillator. I started work on this previously, but I think you picked up from there anyway?

Overall this PR looks really good. I would just change a few minor details and maybe not yet expose the Dormant mode.

Hi,

Thanks for your feedback and code review =) I read extensively your PR and I saw you tried to bind nicely together Clocks, PLLs, Oscillators, ... with extensive typestates and such. I then had a brain meltdown trying to think about how to pick up your work; not criticizing your code (from which I learned a lot) but the complexity of the clocks/PLL/oscillators subsystems and the complexity of "bridging" them together, with all the different abstractions that would be needed : macros, typestate, ...

So I decided on starting from scratch, taking inspiration from your PR as you saw (StableOscillatorToken for example) with the goal of trying to implement one subsystem at a time, starting at the bottom of the foodchain : XOSC.

Not sure if it's the right approach but I figured that it might be easier that way =)

[tdittr]

Oh I can feel you, I had the same brain-meltdown. I think I bit off a bit to much of the problem. Writing it in smaller steps definitely is a good idea. 👍

Maybe at some point in the future when we have all the building blocks we can actually tie them together.

[Nic0w]

This is ready for review again :)

[tdittr]

Looks good to me! 👍

[9names]

Looks good to me too.
After merging, it would be nice to get an example showing how to use this correctly.