104 lines
4.1 KiB
Markdown
104 lines
4.1 KiB
Markdown
# Embassy
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Embassy is a project to make async/await a first-class option for embedded development. For more information and instructions to get started, go to [https://embassy.dev](https://embassy.dev).
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## Executor
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The `embassy::executor` module provides an async/await executor designed for embedded usage.
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- No `alloc`, no heap needed. Task futures are statically allocated.
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- No "fixed capacity" data structures, executor works with 1 or 1000 tasks without needing config/tuning.
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- Integrated timer queue: sleeping is easy, just do `Timer::after(Duration::from_secs(1)).await;`.
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- No busy-loop polling: CPU sleeps when there's no work to do, using interrupts or `WFE/SEV`.
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- Efficient polling: a wake will only poll the woken task, not all of them.
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- 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.
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- Creating multiple executor instances is supported, to run tasks with multiple priority levels. This allows higher-priority tasks to preempt lower-priority tasks.
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## Utils
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`embassy::util` contains some lightweight async/await utilities, mainly helpful for async driver development (signaling a task that an interrupt has occured, for example).
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## HALs
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Hardware Absraction Layers with asynchronous behaviors are provided for a variety of platforms.
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For example, the `embassy-nrf` crate contains implementations for nRF 52 series SoCs.
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- `uarte`: UARTE driver implementing `AsyncBufRead` and `AsyncWrite`.
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- `qspi`: QSPI driver implementing `Flash`.
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- `gpiote`: GPIOTE driver. Allows `await`ing GPIO pin changes. Great for reading buttons or receiving interrupts from external chips.
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- `saadc`: SAADC driver. Provides a full implementation of the one-shot sampling for analog channels.
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- `rtc`: RTC driver implementing `Clock` and `Alarm`, for use with `embassy::executor`.
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## Examples
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Examples are found in the `examples/` folder seperated by the chip manufacturer they are designed to run on. For example:
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* `examples/nrf` are designed to run on the `nrf52840-dk` board (PCA10056) but should be easily adaptable to other nRF52 chips and boards.
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* `examples/rp` are for the RP2040 chip.
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* `examples/stm32` are designed for the STM32F429ZI chip but should be easily adaptable to other STM32F4xx chips.
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* `examples/std` are designed to run locally on your pc.
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### Running examples
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- Setup git submodules (needed for STM32 examples)
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```
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git submodule init
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git submodule update
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```
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- Install `probe-run` with defmt support.
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```
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cargo install probe-run
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```
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- Change directory to the sample's base directory. For example:
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```
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cd examples/nrf
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```
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- Run the example
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For example:
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```
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cargo run --bin blinky
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```
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## Developing Embassy with Rust Analyzer based editors
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The [Rust Analyzer](https://rust-analyzer.github.io/) is used by [Visual Studio Code](https://code.visualstudio.com/)
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and others. Given the multiple targets that Embassy serves, there is no Cargo workspace file. Instead, the Rust Analyzer
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must be told of the target project to work with. In the case of Visual Studio Code,
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please refer to the `.vscode/settings.json` file's `rust-analyzer.linkedProjects`setting.
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## Minimum supported Rust version (MSRV)
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Required nightly version is specified in the `rust-toolchain.toml` file. Nightly is required for:
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- `generic_associated_types`: for trait funcs returning futures.
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- `type_alias_impl_trait`: for trait funcs returning futures implemented with `async{}` blocks, and for `static-executor`.
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Stable support is a non-goal until these features get stabilized.
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## Documentation
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Embassy documentation is located in the `docs/` folder. The documentation is built in [embassy-book](https://github.com/embassy-rs/embassy-book) and published to [https://embassy.dev](https://embassy.dev) by CI.
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## Why the name?
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EMBedded ASYnc! :)
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## License
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This work is licensed under either of
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- Apache License, Version 2.0 ([LICENSE-APACHE](LICENSE-APACHE) or
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http://www.apache.org/licenses/LICENSE-2.0)
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- MIT license ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)
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at your option.
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