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Diffstat (limited to 'book/en/src/by-example/app_idle.md')
| -rw-r--r-- | book/en/src/by-example/app_idle.md | 18 |
1 files changed, 11 insertions, 7 deletions
diff --git a/book/en/src/by-example/app_idle.md b/book/en/src/by-example/app_idle.md index 66f40497..537902a4 100644 --- a/book/en/src/by-example/app_idle.md +++ b/book/en/src/by-example/app_idle.md @@ -1,14 +1,18 @@ # 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) -> !`. +module. This becomes 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. +`init`, `idle` will run *with interrupts enabled* and must never return, +as the `-> !` function signature indicates. +[The Rust type `!` means “never”][nevertype]. -Like in `init`, locally declared resources will have `'static` lifetimes that are safe to access. +[nevertype]: https://doc.rust-lang.org/core/primitive.never.html + +Like in `init`, locally declared resources will have `'static` lifetimes that +are safe to access. The example below shows that `idle` runs after `init`. @@ -21,9 +25,9 @@ $ cargo run --target thumbv7m-none-eabi --example idle {{#include ../../../../ci/expected/idle.run}} ``` -By default the RTIC `idle` task does not try to optimise for any specific targets. +By default, the RTIC `idle` task does not try to optimize for any specific targets. -A common useful optimisation is to enable the [SLEEPONEXIT] and allow the MCU +A common useful optimization is to enable the [SLEEPONEXIT] and allow the MCU to enter sleep when reaching `idle`. >**Caution** some hardware unless configured disables the debug unit during sleep mode. |