monotonic experiments

1 files changed, 138 insertions, 0 deletions

diff --git a/rtic-timer/src/lib.rs b/rtic-timer/src/lib.rs
new file mode 100644
index 0000000..e7051d2
--- /dev/null
+++ b/rtic-timer/src/lib.rs
@@ -0,0 +1,138 @@
+#![no_std]
+
+use core::sync::atomic::{AtomicU32, Ordering};
+use core::{cmp::Ordering, task::Waker};
+use cortex_m::peripheral::{syst::SystClkSource, SYST};
+pub use fugit::{self, ExtU64};
+pub use rtic_monotonic::Monotonic;
+
+mod sll;
+use sll::{IntrusiveSortedLinkedList, Min as IsslMin, Node as IntrusiveNode};
+
+pub struct Timer {
+    cnt: AtomicU32,
+    // queue: IntrusiveSortedLinkedList<'static, WakerNotReady<Mono>, IsslMin>,
+}
+
+#[allow(non_snake_case)]
+#[no_mangle]
+fn SysTick() {
+    // ..
+    let cnt = unsafe {
+        static mut CNT: u32 = 0;
+        &mut CNT
+    };
+
+    *cnt = cnt.wrapping_add(1);
+}
+
+/// Systick implementing `rtic_monotonic::Monotonic` which runs at a
+/// settable rate using the `TIMER_HZ` parameter.
+pub struct Systick<const TIMER_HZ: u32> {
+    systick: SYST,
+    cnt: u64,
+}
+
+impl<const TIMER_HZ: u32> Systick<TIMER_HZ> {
+    /// Provide a new `Monotonic` based on SysTick.
+    ///
+    /// The `sysclk` parameter is the speed at which SysTick runs at. This value should come from
+    /// the clock generation function of the used HAL.
+    ///
+    /// Notice that the actual rate of the timer is a best approximation based on the given
+    /// `sysclk` and `TIMER_HZ`.
+    pub fn new(mut systick: SYST, sysclk: u32) -> Self {
+        // + TIMER_HZ / 2 provides round to nearest instead of round to 0.
+        // - 1 as the counter range is inclusive [0, reload]
+        let reload = (sysclk + TIMER_HZ / 2) / TIMER_HZ - 1;
+
+        assert!(reload <= 0x00ff_ffff);
+        assert!(reload > 0);
+
+        systick.disable_counter();
+        systick.set_clock_source(SystClkSource::Core);
+        systick.set_reload(reload);
+
+        Systick { systick, cnt: 0 }
+    }
+}
+
+impl<const TIMER_HZ: u32> Monotonic for Systick<TIMER_HZ> {
+    const DISABLE_INTERRUPT_ON_EMPTY_QUEUE: bool = false;
+
+    type Instant = fugit::TimerInstantU64<TIMER_HZ>;
+    type Duration = fugit::TimerDurationU64<TIMER_HZ>;
+
+    fn now(&mut self) -> Self::Instant {
+        if self.systick.has_wrapped() {
+            self.cnt = self.cnt.wrapping_add(1);
+        }
+
+        Self::Instant::from_ticks(self.cnt)
+    }
+
+    unsafe fn reset(&mut self) {
+        self.systick.clear_current();
+        self.systick.enable_counter();
+    }
+
+    #[inline(always)]
+    fn set_compare(&mut self, _val: Self::Instant) {
+        // No need to do something here, we get interrupts anyway.
+    }
+
+    #[inline(always)]
+    fn clear_compare_flag(&mut self) {
+        // NOOP with SysTick interrupt
+    }
+
+    #[inline(always)]
+    fn zero() -> Self::Instant {
+        Self::Instant::from_ticks(0)
+    }
+
+    #[inline(always)]
+    fn on_interrupt(&mut self) {
+        if self.systick.has_wrapped() {
+            self.cnt = self.cnt.wrapping_add(1);
+        }
+    }
+}
+
+struct WakerNotReady<Mono>
+where
+    Mono: Monotonic,
+{
+    pub waker: Waker,
+    pub instant: Mono::Instant,
+    pub marker: u32,
+}
+
+impl<Mono> Eq for WakerNotReady<Mono> where Mono: Monotonic {}
+
+impl<Mono> Ord for WakerNotReady<Mono>
+where
+    Mono: Monotonic,
+{
+    fn cmp(&self, other: &Self) -> Ordering {
+        self.instant.cmp(&other.instant)
+    }
+}
+
+impl<Mono> PartialEq for WakerNotReady<Mono>
+where
+    Mono: Monotonic,
+{
+    fn eq(&self, other: &Self) -> bool {
+        self.instant == other.instant
+    }
+}
+
+impl<Mono> PartialOrd for WakerNotReady<Mono>
+where
+    Mono: Monotonic,
+{
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        Some(self.cmp(other))
+    }
+}