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Diffstat (limited to 'book/en/src/by-example/app_idle.md')
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diff --git a/book/en/src/by-example/app_idle.md b/book/en/src/by-example/app_idle.md new file mode 100644 index 0000000..1eb1472 --- /dev/null +++ b/book/en/src/by-example/app_idle.md @@ -0,0 +1,27 @@ +# The background task `#[idle]` + +A function marked with the `idle` attribute can optionally appear in the +module. This function is used as the special *idle task* and must have +signature `fn(idle::Context) -> !`. + +When present, the runtime will execute the `idle` task after `init`. Unlike +`init`, `idle` will run *with interrupts enabled* and it's not allowed to return +so it must run forever. + +When no `idle` function is declared, the runtime sets the [SLEEPONEXIT] bit and +then sends the microcontroller to sleep after running `init`. + +[SLEEPONEXIT]: https://developer.arm.com/docs/100737/0100/power-management/sleep-mode/sleep-on-exit-bit + +Like in `init`, locally declared resources will have `'static` lifetimes that are safe to access. + +The example below shows that `idle` runs after `init`. + +``` rust +{{#include ../../../../examples/idle.rs}} +``` + +``` console +$ cargo run --target thumbv7m-none-eabi --example idle +{{#include ../../../../ci/expected/idle.run}} +``` |