Merge #694

694: RTIC 2 r=AfoHT a=korken89



Co-authored-by: Emil Fresk <emil.fresk@gmail.com>
Co-authored-by: Per Lindgren <per.lindgren@ltu.se>

1 files changed, 18 insertions, 17 deletions

diff --git a/book/en/src/by-example/app_idle.md b/book/en/src/by-example/app_idle.md
index 537902a..cbfd7ba 100644
--- a/book/en/src/by-example/app_idle.md
+++ b/book/en/src/by-example/app_idle.md
@@ -1,52 +1,53 @@
 # The background task `#[idle]`
 
-A function marked with the `idle` attribute can optionally appear in the
-module. This becomes the special *idle task* and must have signature
-`fn(idle::Context) -> !`.
+A function marked with the `idle` attribute can optionally appear in the 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 must never return,
-as the `-> !` function signature indicates.
+When present, the runtime will execute the `idle` task after `init`. Unlike `init`, `idle` will run *with interrupts enabled* and must never return, as the `-> !` function signature indicates.
 [The Rust type `!` means “never”][nevertype].
 
 [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.
+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}}
+{{#include ../../../../rtic/examples/idle.rs}}
 ```
 
 ``` console
 $ cargo run --target thumbv7m-none-eabi --example idle
-{{#include ../../../../ci/expected/idle.run}}
+```
+
+``` console
+{{#include ../../../../rtic/ci/expected/idle.run}}
 ```
 
 By default, the RTIC `idle` task does not try to optimize for any specific targets.
 
-A common useful optimization is to enable the [SLEEPONEXIT] and allow the MCU
-to enter sleep when reaching `idle`.
+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.
+>**Caution**: some hardware unless configured disables the debug unit during sleep mode.
 >
 >Consult your hardware specific documentation as this is outside the scope of RTIC.
 
 The following example shows how to enable sleep by setting the
-[`SLEEPONEXIT`][SLEEPONEXIT] and providing a custom `idle` task replacing the
-default [`nop()`][NOP] with [`wfi()`][WFI].
+[`SLEEPONEXIT`][SLEEPONEXIT] and providing a custom `idle` task replacing the default [`nop()`][NOP] with [`wfi()`][WFI].
 
 [SLEEPONEXIT]: https://developer.arm.com/docs/100737/0100/power-management/sleep-mode/sleep-on-exit-bit
 [WFI]: https://developer.arm.com/documentation/dui0662/b/The-Cortex-M0--Instruction-Set/Miscellaneous-instructions/WFI
 [NOP]: https://developer.arm.com/documentation/dui0662/b/The-Cortex-M0--Instruction-Set/Miscellaneous-instructions/NOP
 
 ``` rust
-{{#include ../../../../examples/idle-wfi.rs}}
+{{#include ../../../../rtic/examples/idle-wfi.rs}}
 ```
 
 ``` console
 $ cargo run --target thumbv7m-none-eabi --example idle-wfi
-{{#include ../../../../ci/expected/idle-wfi.run}}
 ```
+
+``` console
+{{#include ../../../../rtic/ci/expected/idle-wfi.run}}
+```
+
+> **Notice**: The `idle` task cannot be used together with *software* tasks running at priority zero. The reason is that `idle` is running as a non-returning Rust function at priority zero. Thus there would be no way for an executor at priority zero to give control to *software* tasks at the same priority.