7cb34760c4
427: New nrf PPI api (with DPPI support for nRF91 & nRF53) r=Dirbaio a=diondokter - Added _ppi and _dppi features to distinguish between the new and the old peripheral. - Removed ConfigurableChannel and added capacity numbers to the channels - Replaced the PPI api with a new one using the DPPI terminology (publish & subscribe) - Updated all tasks and event registers for DPPI My proposal for the new API. Tested on my nRF52840 and nRF9160. Biggest changes for nRF52 is that there's no longer a distinction made between fork task and normal task. You now subscribe tasks to a channel and at runtime it is checked whether or not there's still room for another subscription. Same for events. There are differences between the PPI and DPPI though: - With the PPI you have a limited amount of tasks and events per channel, but a task or event can be used on multiple channels at the same time. - With the DPPI you have an unlimited amount of tasks and events per channel, but every task or event can only be used on 1 channel. This is all checked at runtime. Currently you need to track which tasks and events are assigned to a channel in order to unassign them. For the PPI this data is stored centrally in the registers, so it would be easy to create e.g. `clear_all` and `get_subscribed_tasks` functions. But for the DPPI that data is stored decentrally and so would need some manual tracking. If there are requests for tracking functionality, then it should be able to be made relatively easy. But for now this API is fine I think. Co-authored-by: Dion Dokter <dion@tweedegolf.com> Co-authored-by: Dario Nieuwenhuis <dirbaio@dirbaio.net>
Embassy
Embassy is a project to make async/await a first-class option for embedded development. For more information and instructions to get started, click here.
Traits and types
embassy provides a set of traits and types specifically designed for async usage.
embassy::io:AsyncBufRead,AsyncWrite. Traits for byte-stream IO, essentiallyno_stdcompatible versions offutures::io.embassy::traits::flash: Flash device trait.embassy::time:ClockandAlarmtraits. Std-likeDurationandInstant.- More traits for SPI, I2C, UART async HAL coming soon.
Executor
The embassy::executor module provides an async/await executor designed for embedded usage.
- No
alloc, no heap needed. Task futures are statically allocated. - No "fixed capacity" data structures, executor works with 1 or 1000 tasks without needing config/tuning.
- Integrated timer queue: sleeping is easy, just do
Timer::after(Duration::from_secs(1)).await;. - No busy-loop polling: CPU sleeps when there's no work to do, using interrupts or
WFE/SEV. - Efficient polling: a wake will only poll the woken task, not all of them.
- Fair: a task can't monopolize CPU time even if it's constantly being woken. All other tasks get a chance to run before a given task gets polled for the second time.
- Creating multiple executor instances is supported, to run tasks with multiple priority levels. This allows higher-priority tasks to preempt lower-priority tasks.
Utils
embassy::util contains some lightweight async/await utilities, mainly helpful for async driver development (signaling a task that an interrupt has occured, for example).
embassy-nrf
The embassy-nrf crate contains implementations for nRF 52 series SoCs.
-
uarte: UARTE driver implementingAsyncBufReadandAsyncWrite. -
qspi: QSPI driver implementingFlash. -
gpiote: GPIOTE driver. Allowsawaiting GPIO pin changes. Great for reading buttons or receiving interrupts from external chips. -
saadc: SAADC driver. Provides a full implementation of the one-shot sampling for analog channels. -
rtc: RTC driver implementingClockandAlarm, for use withembassy::executor.
Examples
Examples are found in the examples/ folder seperated by the chip manufacturer they are designed to run on:
examples/nrfare designed to run on thenrf52840-dkboard (PCA10056) but should be easily adaptable to other nRF52 chips and boards.examples/rpare for the RP2040 chip.examples/stm32are designed for the STM32F429ZI chip but should be easily adaptable to other STM32F4xx chips.examples/stdare designed to run locally on your pc.
Running examples
- Setup git submodules (needed for STM32 examples)
git submodule init
git submodule update
- Install
probe-runwith defmt support.
cargo install probe-run
- Run the example
cargo run --bin rtc_async
Minimum supported Rust version (MSRV)
Required nightly version is specified in the rust-toolchain.toml file. Nightly is required for:
generic_associated_types: for trait funcs returning futures.type_alias_impl_trait: for trait funcs returning futures implemented withasync{}blocks, and forstatic-executor.
Stable support is a non-goal until these features get stabilized.
Why the name?
EMBedded ASYnc! :)
License
This work is licensed under either of
- Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
- MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)
at your option.