Implement usb_device for rp2040
Limitations
- RP2040-E5 (Device enumeration workaround) is not implemented
- Suspend/resume is not implemented
- VBus detection is not tested and may not be fully implemented
We updated the behavior of boot2 so that there is now no default bootloader.
Pico_explorer_showcase was the only BSP still using git:main, pin
it to the last git commit before https://github.com/rp-rs/rp2040-boot2-rs/pull/7
* Improve clock frequency stuff for uninitialized clocks
- Made clocks singletons so the frequency handling actually works as expected
- Added initial frequencies
- Improved the docs
- Added a Clock trait
* Add pico examples.
These have the benefit of knowing which external crystal is attached.
Even though it always should be a 12 MHz crystal.
Thus we can setup the clocks properly
I also changed the rp2040 examples to work out of the box for pico boards since that will probably be used most of the time
Bring in line with atsamd-hal GPIO v2
Copied as much as possible. Docs lifted mostly as-is.
Also add sample BSP for the Feather RP2040 in boards/feather_rp2040
May include a few random fixes from currently futile attempt to get doctests working.
