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Merge #552

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552: Remove example impl and have a list of example impls instead r=AfoHT a=korken89



Co-authored-by: Emil Fresk <emil.fresk@gmail.com>
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bors[bot] 2021-11-10 09:35:29 +00:00 committed by GitHub
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58
book/en/src/by-example/tips_monotonic_impl.md
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@ -11,55 +11,19 @@ RTIC 0.6 we have moved to assume the user has a time library, e.g. [`fugit`] or
as the basis for all time-based operations when implementing `Monotonic`. This is why in RTIC 0.6
it is almost trivial to implement the `Monotonic` trait and use any timer in a system for scheduling.
The trait documents the requirements for each method, however a small PoC implementation is provided
below.
The trait documents the requirements for each method, however below you can find a list of
implementations in the wild that can be used as inspiration:
- [`STM32F411 timers`], implemented for the 32-bit timers
- [`Systick based`], runs at a fixed rate - some overhead but simple
- [`DWT and Systick based`], a more efficient `Systick` based implementation, but requires `DWT`
If you know of more implementations feel free to add them to this list.
[`rtic_monotonic::Monotonic`]: https://docs.rs/rtic-monotonic/
[`fugit`]: https://docs.rs/fugit/
[`embedded_time`]: https://docs.rs/embedded_time/
[`STM32F411 timers`]: https://github.com/kalkyl/f411-rtic/blob/main/src/bin/mono.rs
[`Systick based`]: https://github.com/rtic-rs/systick-monotonic
[`DWT and Systick based`]: https://github.com/rtic-rs/dwt-systick-monotonic
```rust
pub use fugit::{self, ExtU32};
use rtic_monotonic::Monotonic;
/// Example wrapper struct for a timer
pub struct Timer<const TIMER_HZ: u32> {
tim: TIM2,
}
impl<const TIMER_HZ: u32> Monotonic for Timer<TIMER_HZ> {
type Instant = fugit::TimerInstantU32<TIMER_HZ>;
type Duration = fugit::TimerDurationU32<TIMER_HZ>;
fn now(&mut self) -> Self::Instant {
// Read the timer count
Self::Instant::from_ticks(Self::count())
}
fn zero() -> Self::Instant {
// This is used while the app is in `#[init]`, if the system cannot
// support time in `#[init]` this can also be a `panic!(..)`
Self::Instant::from_ticks(0)
}
unsafe fn reset(&mut self) {
// Reset timer counter
self.tim.cnt.write(|_, w| w.bits(0));
// Since reset is only called once, we use it to enable
// the interrupt generation bit.
self.tim.dier.modify(|_, w| w.cc1ie().set_bit());
}
fn set_compare(&mut self, instant: Instant<Self>) {
// Use Compare channel 1 for Monotonic
self.tim
.ccr1
.write(|w| w.ccr().bits(instant.ticks()));
}
fn clear_compare_flag(&mut self) {
self.tim.sr.modify(|_, w| w.cc1if().clear_bit());
}
}
```