added typestate to nrf-Timer

useful for hooking up the PPI to an Event without needing interrupt
tested with buffered_uart example on nRF52840-DK

embassy-nrf/src/timer.rs

@@ -27,6 +27,8 @@ pub(crate) mod sealed {
         fn waker(n: usize) -> &'static AtomicWaker;
     }
     pub trait ExtendedInstance {}
+
+    pub trait TimerType {}
 }
 
 pub trait Instance: Unborrow<Target = Self> + sealed::Instance + 'static + Send {
@@ -84,11 +86,25 @@ pub enum Frequency {
 ///
 /// It has either 4 or 6 Capture/Compare registers, which can be used to capture the current state of the counter
 /// or trigger an event when the counter reaches a certain value.
-pub struct Timer<'d, T: Instance> {
-    phantom: PhantomData<&'d mut T>,
+
+pub trait TimerType: sealed::TimerType {}
+
+pub enum Awaitable {}
+pub enum NotAwaitable {}
+
+impl sealed::TimerType for Awaitable {}
+impl sealed::TimerType for NotAwaitable {}
+impl TimerType for Awaitable {}
+impl TimerType for NotAwaitable {}
+
+pub type AwaitableTimer<'d, T> = Timer<'d, T, Awaitable>;
+pub type NotAwaitableTimer<'d, T> = Timer<'d, T, NotAwaitable>;
+
+pub struct Timer<'d, T: Instance, I: TimerType> {
+    phantom: PhantomData<(&'d mut T, I)>,
 }
 
-impl<'d, T: Instance> Timer<'d, T> {
+impl<'d, T: Instance> Timer<'d, T, Awaitable> {
     pub fn new(
         timer: impl Unborrow<Target = T> + 'd,
         irq: impl Unborrow<Target = T::Interrupt> + 'd,
@@ -101,11 +117,18 @@ impl<'d, T: Instance> Timer<'d, T> {
 
         Self::new_irqless(timer)
     }
+}
+impl<'d, T: Instance> Timer<'d, T, NotAwaitable> {
+    pub fn new(timer: impl Unborrow<Target = T> + 'd) -> Self {
+        Self::new_irqless(timer)
+    }
+}
 
+impl<'d, T: Instance, I: TimerType> Timer<'d, T, I> {
     /// Create a `Timer` without an interrupt, meaning `Cc::wait` won't work.
     ///
     /// This is used by `Uarte` internally.
-    pub(crate) fn new_irqless(_timer: impl Unborrow<Target = T> + 'd) -> Self {
+    fn new_irqless(_timer: impl Unborrow<Target = T> + 'd) -> Self {
         let regs = T::regs();
 
         let mut this = Self {
@@ -208,7 +231,7 @@ impl<'d, T: Instance> Timer<'d, T> {
     ///
     /// # Panics
     /// Panics if `n` >= the number of CC registers this timer has (4 for a normal timer, 6 for an extended timer).
-    pub fn cc(&mut self, n: usize) -> Cc<T> {
+    pub fn cc(&mut self, n: usize) -> Cc<T, I> {
         if n >= T::CCS {
             panic!(
                 "Cannot get CC register {} of timer with {} CC registers.",
@@ -219,6 +242,7 @@ impl<'d, T: Instance> Timer<'d, T> {
         Cc {
             n,
             phantom: PhantomData,
+            phantom2: PhantomData,
         }
     }
 }
@@ -230,12 +254,16 @@ impl<'d, T: Instance> Timer<'d, T> {
 ///
 /// The timer will fire the register's COMPARE event when its counter reaches the value stored in the register.
 /// When the register's CAPTURE task is triggered, the timer will store the current value of its counter in the register
-pub struct Cc<'a, T: Instance> {
+pub struct Cc<'a, T: Instance, I: TimerType> {
     n: usize,
     phantom: PhantomData<&'a mut T>,
+    phantom2: PhantomData<I>,
 }
 
-impl<'a, T: Instance> Cc<'a, T> {
+impl<'a, T: Instance> Cc<'a, T, Awaitable> {}
+impl<'a, T: Instance> Cc<'a, T, NotAwaitable> {}
+
+impl<'a, T: Instance, I: TimerType> Cc<'a, T, I> {
     /// Get the current value stored in the register.
     pub fn read(&self) -> u32 {
         T::regs().cc[self.n].read().cc().bits()