640: Skip EasyDMA slice location check for empty slices and copy data if necessary r=Dirbaio a=TilBlechschmidt
As discussed, this PR makes the following changes:
- Ignore pointer location of zero-length slices (fixes#631)
- Change default functions so they copy the tx buffer if it does not reside in RAM
- Introduce new variants for `write`, `transfer`, and their blocking versions which fails instead of copying
- Add documentation about the motivation behind all these variants
<img width="984" alt="image" src="https://user-images.githubusercontent.com/5037967/155415788-c2cd1055-9289-4004-959d-be3b1934a439.png">
Remaining TODOs:
- [x] Change copying behaviour for other peripherals
- [x] TWI
- [x] UART
- [x] Add module-level documentation regarding EasyDMA and `_from_ram` method variants
`@Dirbaio` it probably makes sense for you to review it now before I "copy" over the changes to the other two peripherals.
Co-authored-by: Til Blechschmidt <til@blechschmidt.de>
Starting the sampling task prior to starting the SAADC peripheral can lead to unexpected buffer behaviour with multiple channels. We now provide an init callback at the point where the SAADC has started for the first time. This callback can be used to kick off sampling via PPI.
We also need to trigger the SAADC to start sampling the next buffer when the previous one is ended so that we do not drop samples - the major benefit of double buffering.
As a bonus we provide a calibrate method as it is recommended to use before starting up the sampling.
The example has been updated to illustrate these new features.
613: Rust stable support r=Dirbaio a=Dirbaio
This PR adds (limited) stable Rust support!
The drawbacks are:
- No `#[embassy::task]`, `#[embassy::main]`. (requires `type_alias_impl_trait`). You have to manually allocate the tasks somewhere they'll live forever. See [example](https://github.com/embassy-rs/embassy/blob/master/examples/nrf/src/bin/raw_spawn.rs)
- No async trait impls (requires GATs). Note that the full API surface of HALs is still available through inherent methods: #552#581
- Some stuff is not constructible in const (requires `const_fn_trait_bound`), although there's an (ugly) workaround for the generic `Mutex`.
So it's not that bad in the end, it's fully usable for shipping production-ready firmwares. We'll still recommend nightly as the default, until GATs and `type_alias_impl_trait` are stable.
Co-authored-by: Dario Nieuwenhuis <dirbaio@dirbaio.net>
