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Modern embedded framework, using Rust and async.
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Timo Kröger a7c03e4cb6 uarte: Only stop RX forcefully when a reception is running 
The STOPRX task always triggers a timeout of ~55bit times until the
RXTO event is generated. Before we disabled the receiver only after
the timeout.
With this change the receiver is stopped right after reception has ended
because the DMA buffer is full.
For forced RX aborts like `stop()` or on drop still need to wait for the
RXTO event before disabling the receiver.
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README.md

Embassy

Embassy is a project to make async/await a first-class option for embedded development.

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, essentially no_std compatible versions of futures::io.
  • embassy::flash: Flash device trait.
  • embassy::time: Clock and Alarm traits. Std-like Duration and Instant.
  • 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 implementing AsyncBufRead and AsyncWrite.
  • qspi: QSPI driver implementing Flash.
  • gpiote: GPIOTE driver. Allows awaiting GPIO pin changes. Great for reading buttons or receiving interrupts from external chips.
  • rtc: RTC driver implementing Clock and Alarm, for use with embassy::executor.

Running the examples

Examples are for the nRF52840 chip but should be easily adaptable to other nRF52 chips.

GPIO pins are set up for the nrf52840-dk board (PCA10056)

  • Install probe-run with defmt support.
cargo install --git https://github.com/knurling-rs/probe-run --branch main --features defmt
  • Run the example
cargo run --bin rtc_async

Minimum supported Rust version (MSRV)

Only recent nighly supported. Nightly is required for:

  • generic_associated_types: for trait funcs returning futures.
  • type_alias_impl_trait: for trait funcs returning futures implemented with async{} blocks, and for static-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

at your option.