Crate embassy_executor

embassy-executor

An async/await executor designed for embedded usage.

• No alloc, no heap needed.
• Tasks are statically allocated. Each task gets its own static, with the exact size to hold the task (or multiple instances of it, if using pool_size) calculated automatically at compile time. If tasks don’t fit in RAM, this is detected at compile time by the linker. Runtime panics due to running out of memory are not possible.
• 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_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.

Feature flags

• nightly — Enable nightly-only features

Architecture

• arch-std — std
• arch-cortex-m — Cortex-M
• arch-riscv32 — RISC-V 32
• arch-wasm — WASM
• arch-avr — AVR
• arch-spin — spin (architecture agnostic; never sleeps)

Executor

• executor-thread — Enable the thread-mode executor (using WFE/SEV in Cortex-M, WFI in other embedded archs)
• executor-interrupt — Enable the interrupt-mode executor (available in Cortex-M only)
• trace — Enable tracing support (adds some overhead)
• rtos-trace — Enable support for rtos-trace framework

Timer Item Payload Size

Sets the size of the payload for timer items, allowing integrated timer implementors to store additional data in the timer item. The payload field will be aligned to this value as well. If these features are not defined, the timer item will contain no payload field.

• timer-item-payload-size-1 — 1 bytes
• timer-item-payload-size-2 — 2 bytes
• timer-item-payload-size-4 — 4 bytes
• timer-item-payload-size-8 — 8 bytes

Modules

raw

Raw executor.

Structs

Executor

WASM executor, wasm_bindgen to schedule tasks on the JS event loop.

SendSpawner

Handle to spawn tasks into an executor from any thread.

SpawnToken

Token to spawn a newly-created task in an executor.

Spawner

Handle to spawn tasks into an executor.

Enums

SpawnError

Error returned when spawning a task.

Attribute Macros

main

Creates a new executor instance and declares an application entry point for WASM spawning the corresponding function body as an async task.

task

Declares an async task that can be run by embassy-executor. The optional pool_size parameter can be used to specify how many concurrent tasks can be spawned (default is 1) for the function.