diff options
| author | Henrik Tjäder <henrik@grepit.se> | 2021-12-14 21:52:57 +0100 |
|---|---|---|
| committer | Henrik Tjäder <henrik@grepit.se> | 2021-12-14 22:18:17 +0100 |
| commit | 8c8f7f12c3bfc132b7fad9df80559e474ed66b66 (patch) | |
| tree | eedf420265c65ec5430e3c8bcddd5e8ca73db86a /book | |
| parent | 3741d431bed5a4799c7fdb20de5950a0964569e5 (diff) | |
Idle: Switch to NOP instead of WFI
Add example how to get old WFI behaviour
Diffstat (limited to 'book')
| -rw-r--r-- | book/en/src/by-example/app_idle.md | 31 |
1 files changed, 26 insertions, 5 deletions
diff --git a/book/en/src/by-example/app_idle.md b/book/en/src/by-example/app_idle.md index 1eb1472..66f4049 100644 --- a/book/en/src/by-example/app_idle.md +++ b/book/en/src/by-example/app_idle.md @@ -8,11 +8,6 @@ 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`. @@ -25,3 +20,29 @@ The example below shows that `idle` runs after `init`. $ 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. + +A common useful optimisation 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. +> +>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]: 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}} +``` + +``` console +$ cargo run --target thumbv7m-none-eabi --example idle-wfi +{{#include ../../../../ci/expected/idle-wfi.run}} +``` |