Merge remote-tracking branch 'origin/main' into nrf-pdm

11 files changed, 902 insertions, 101 deletions

diff --git a/embassy-time/src/delay.rs b/embassy-time/src/delay.rs
index d010fff98..cf1918724 100644
--- a/embassy-time/src/delay.rs
+++ b/embassy-time/src/delay.rs
@@ -18,39 +18,29 @@ pub struct Delay;
 mod eh1 {
     use super::*;
 
-    impl embedded_hal_1::delay::blocking::DelayUs for Delay {
-        type Error = core::convert::Infallible;
-
-        fn delay_us(&mut self, us: u32) -> Result<(), Self::Error> {
-            Ok(block_for(Duration::from_micros(us as u64)))
+    impl embedded_hal_1::delay::DelayUs for Delay {
+        fn delay_us(&mut self, us: u32) {
+            block_for(Duration::from_micros(us as u64))
         }
 
-        fn delay_ms(&mut self, ms: u32) -> Result<(), Self::Error> {
-            Ok(block_for(Duration::from_millis(ms as u64)))
+        fn delay_ms(&mut self, ms: u32) {
+            block_for(Duration::from_millis(ms as u64))
         }
     }
 }
 
-cfg_if::cfg_if! {
-    if #[cfg(all(feature = "unstable-traits", feature = "nightly"))] {
-        use crate::Timer;
-        use core::future::Future;
-        use futures_util::FutureExt;
-
-        impl embedded_hal_async::delay::DelayUs for Delay {
-            type Error = core::convert::Infallible;
-
-            type DelayUsFuture<'a> = impl Future<Output = Result<(), Self::Error>> + 'a where Self: 'a;
-
-            fn delay_us(&mut self, micros: u32) -> Self::DelayUsFuture<'_> {
-                Timer::after(Duration::from_micros(micros as _)).map(Ok)
-            }
+#[cfg(all(feature = "unstable-traits", feature = "nightly"))]
+mod eha {
+    use super::*;
+    use crate::Timer;
 
-            type DelayMsFuture<'a> = impl Future<Output = Result<(), Self::Error>> + 'a where Self: 'a;
+    impl embedded_hal_async::delay::DelayUs for Delay {
+        async fn delay_us(&mut self, micros: u32) {
+            Timer::after(Duration::from_micros(micros as _)).await
+        }
 
-            fn delay_ms(&mut self, millis: u32) -> Self::DelayMsFuture<'_> {
-                Timer::after(Duration::from_millis(millis as _)).map(Ok)
-            }
+        async fn delay_ms(&mut self, millis: u32) {
+            Timer::after(Duration::from_millis(millis as _)).await
         }
     }
 }
diff --git a/embassy-time/src/driver.rs b/embassy-time/src/driver.rs
index 79ae14b91..5fe7becaf 100644
--- a/embassy-time/src/driver.rs
+++ b/embassy-time/src/driver.rs
@@ -36,7 +36,7 @@
 //! ```
 //! use embassy_time::driver::{Driver, AlarmHandle};
 //!
-//! struct MyDriver{}; // not public!
+//! struct MyDriver{} // not public!
 //! embassy_time::time_driver_impl!(static DRIVER: MyDriver = MyDriver{});
 //!
 //! impl Driver for MyDriver {
@@ -49,7 +49,7 @@
 //!     fn set_alarm_callback(&self, alarm: AlarmHandle, callback: fn(*mut ()), ctx: *mut ()) {
 //!         todo!()
 //!     }
-//!     fn set_alarm(&self, alarm: AlarmHandle, timestamp: u64) {
+//!     fn set_alarm(&self, alarm: AlarmHandle, timestamp: u64) -> bool {
 //!         todo!()
 //!     }
 //! }
@@ -105,20 +105,21 @@ pub trait Driver: Send + Sync + 'static {
     /// Sets an alarm at the given timestamp. When the current timestamp reaches the alarm
     /// timestamp, the provided callback function will be called.
     ///
-    /// If `timestamp` is already in the past, the alarm callback must be immediately fired.
-    /// In this case, it is allowed (but not mandatory) to call the alarm callback synchronously from `set_alarm`.
+    /// The `Driver` implementation should guarantee that the alarm callback is never called synchronously from `set_alarm`.
+    /// Rather - if `timestamp` is already in the past - `false` should be returned and alarm should not be set,
+    /// or alternatively, the driver should return `true` and arrange to call the alarm callback as soon as possible, but not synchronously.
     ///
     /// When callback is called, it is guaranteed that now() will return a value greater or equal than timestamp.
     ///
     /// Only one alarm can be active at a time for each AlarmHandle. This overwrites any previously-set alarm if any.
-    fn set_alarm(&self, alarm: AlarmHandle, timestamp: u64);
+    fn set_alarm(&self, alarm: AlarmHandle, timestamp: u64) -> bool;
 }
 
 extern "Rust" {
     fn _embassy_time_now() -> u64;
     fn _embassy_time_allocate_alarm() -> Option<AlarmHandle>;
     fn _embassy_time_set_alarm_callback(alarm: AlarmHandle, callback: fn(*mut ()), ctx: *mut ());
-    fn _embassy_time_set_alarm(alarm: AlarmHandle, timestamp: u64);
+    fn _embassy_time_set_alarm(alarm: AlarmHandle, timestamp: u64) -> bool;
 }
 
 /// See [`Driver::now`]
@@ -139,7 +140,7 @@ pub fn set_alarm_callback(alarm: AlarmHandle, callback: fn(*mut ()), ctx: *mut (
 }
 
 /// See [`Driver::set_alarm`]
-pub fn set_alarm(alarm: AlarmHandle, timestamp: u64) {
+pub fn set_alarm(alarm: AlarmHandle, timestamp: u64) -> bool {
     unsafe { _embassy_time_set_alarm(alarm, timestamp) }
 }
 
@@ -167,7 +168,7 @@ macro_rules! time_driver_impl {
         }
 
         #[no_mangle]
-        fn _embassy_time_set_alarm(alarm: $crate::driver::AlarmHandle, timestamp: u64) {
+        fn _embassy_time_set_alarm(alarm: $crate::driver::AlarmHandle, timestamp: u64) -> bool {
             <$t as $crate::driver::Driver>::set_alarm(&$name, alarm, timestamp)
         }
     };
diff --git a/embassy-time/src/driver_std.rs b/embassy-time/src/driver_std.rs
index 2ddb2e604..32db47a37 100644
--- a/embassy-time/src/driver_std.rs
+++ b/embassy-time/src/driver_std.rs
@@ -1,10 +1,11 @@
-use std::cell::UnsafeCell;
+use core::sync::atomic::{AtomicU8, Ordering};
+use std::cell::{RefCell, UnsafeCell};
 use std::mem::MaybeUninit;
 use std::sync::{Condvar, Mutex, Once};
 use std::time::{Duration as StdDuration, Instant as StdInstant};
 use std::{mem, ptr, thread};
 
-use atomic_polyfill::{AtomicU8, Ordering};
+use critical_section::Mutex as CsMutex;
 
 use crate::driver::{AlarmHandle, Driver};
 
@@ -35,7 +36,10 @@ struct TimeDriver {
     alarm_count: AtomicU8,
 
     once: Once,
-    alarms: UninitCell<Mutex<[AlarmState; ALARM_COUNT]>>,
+    // The STD Driver implementation requires the alarms' mutex to be reentrant, which the STD Mutex isn't
+    // Fortunately, mutexes based on the `critical-section` crate are reentrant, because the critical sections
+    // themselves are reentrant
+    alarms: UninitCell<CsMutex<RefCell<[AlarmState; ALARM_COUNT]>>>,
     zero_instant: UninitCell<StdInstant>,
     signaler: UninitCell<Signaler>,
 }
@@ -53,7 +57,7 @@ crate::time_driver_impl!(static DRIVER: TimeDriver = TimeDriver {
 impl TimeDriver {
     fn init(&self) {
         self.once.call_once(|| unsafe {
-            self.alarms.write(Mutex::new([ALARM_NEW; ALARM_COUNT]));
+            self.alarms.write(CsMutex::new(RefCell::new([ALARM_NEW; ALARM_COUNT])));
             self.zero_instant.write(StdInstant::now());
             self.signaler.write(Signaler::new());
 
@@ -66,25 +70,38 @@ impl TimeDriver {
         loop {
             let now = DRIVER.now();
 
-            let mut next_alarm = u64::MAX;
-            {
-                let alarms = &mut *unsafe { DRIVER.alarms.as_ref() }.lock().unwrap();
-                for alarm in alarms {
-                    if alarm.timestamp <= now {
-                        alarm.timestamp = u64::MAX;
+            let next_alarm = critical_section::with(|cs| {
+                let alarms = unsafe { DRIVER.alarms.as_ref() }.borrow(cs);
+                loop {
+                    let pending = alarms
+                        .borrow_mut()
+                        .iter_mut()
+                        .find(|alarm| alarm.timestamp <= now)
+                        .map(|alarm| {
+                            alarm.timestamp = u64::MAX;
 
-                        // Call after clearing alarm, so the callback can set another alarm.
+                            (alarm.callback, alarm.ctx)
+                        });
 
+                    if let Some((callback, ctx)) = pending {
                         // safety:
                         // - we can ignore the possiblity of `f` being unset (null) because of the safety contract of `allocate_alarm`.
                         // - other than that we only store valid function pointers into alarm.callback
-                        let f: fn(*mut ()) = unsafe { mem::transmute(alarm.callback) };
-                        f(alarm.ctx);
+                        let f: fn(*mut ()) = unsafe { mem::transmute(callback) };
+                        f(ctx);
                     } else {
-                        next_alarm = next_alarm.min(alarm.timestamp);
+                        // No alarm due
+                        break;
                     }
                 }
-            }
+
+                alarms
+                    .borrow()
+                    .iter()
+                    .map(|alarm| alarm.timestamp)
+                    .min()
+                    .unwrap_or(u64::MAX)
+            });
 
             // Ensure we don't overflow
             let until = zero
@@ -121,18 +138,24 @@ impl Driver for TimeDriver {
 
     fn set_alarm_callback(&self, alarm: AlarmHandle, callback: fn(*mut ()), ctx: *mut ()) {
         self.init();
-        let mut alarms = unsafe { self.alarms.as_ref() }.lock().unwrap();
-        let alarm = &mut alarms[alarm.id() as usize];
-        alarm.callback = callback as *const ();
-        alarm.ctx = ctx;
+        critical_section::with(|cs| {
+            let mut alarms = unsafe { self.alarms.as_ref() }.borrow_ref_mut(cs);
+            let alarm = &mut alarms[alarm.id() as usize];
+            alarm.callback = callback as *const ();
+            alarm.ctx = ctx;
+        });
     }
 
-    fn set_alarm(&self, alarm: AlarmHandle, timestamp: u64) {
+    fn set_alarm(&self, alarm: AlarmHandle, timestamp: u64) -> bool {
         self.init();
-        let mut alarms = unsafe { self.alarms.as_ref() }.lock().unwrap();
-        let alarm = &mut alarms[alarm.id() as usize];
-        alarm.timestamp = timestamp;
-        unsafe { self.signaler.as_ref() }.signal();
+        critical_section::with(|cs| {
+            let mut alarms = unsafe { self.alarms.as_ref() }.borrow_ref_mut(cs);
+            let alarm = &mut alarms[alarm.id() as usize];
+            alarm.timestamp = timestamp;
+            unsafe { self.signaler.as_ref() }.signal();
+        });
+
+        true
     }
 }
 
diff --git a/embassy-time/src/driver_wasm.rs b/embassy-time/src/driver_wasm.rs
index e4497e6a2..0f672dc75 100644
--- a/embassy-time/src/driver_wasm.rs
+++ b/embassy-time/src/driver_wasm.rs
@@ -1,9 +1,9 @@
+use core::sync::atomic::{AtomicU8, Ordering};
 use std::cell::UnsafeCell;
 use std::mem::MaybeUninit;
 use std::ptr;
 use std::sync::{Mutex, Once};
 
-use atomic_polyfill::{AtomicU8, Ordering};
 use wasm_bindgen::prelude::*;
 use wasm_timer::Instant as StdInstant;
 
@@ -90,15 +90,23 @@ impl Driver for TimeDriver {
         }));
     }
 
-    fn set_alarm(&self, alarm: AlarmHandle, timestamp: u64) {
+    fn set_alarm(&self, alarm: AlarmHandle, timestamp: u64) -> bool {
         self.init();
         let mut alarms = unsafe { self.alarms.as_ref() }.lock().unwrap();
         let alarm = &mut alarms[alarm.id() as usize];
-        let timeout = (timestamp - self.now()) as u32;
         if let Some(token) = alarm.token {
             clearTimeout(token);
         }
-        alarm.token = Some(setTimeout(alarm.closure.as_ref().unwrap(), timeout / 1000));
+
+        let now = self.now();
+        if timestamp <= now {
+            false
+        } else {
+            let timeout = (timestamp - now) as u32;
+            alarm.token = Some(setTimeout(alarm.closure.as_ref().unwrap(), timeout / 1000));
+
+            true
+        }
     }
 }
 
diff --git a/embassy-time/src/duration.rs b/embassy-time/src/duration.rs
index dc4f16bd4..8366455be 100644
--- a/embassy-time/src/duration.rs
+++ b/embassy-time/src/duration.rs
@@ -1,7 +1,7 @@
 use core::fmt;
 use core::ops::{Add, AddAssign, Div, DivAssign, Mul, MulAssign, Sub, SubAssign};
 
-use super::{GCD_1K, GCD_1M, TICKS_PER_SECOND};
+use super::{GCD_1K, GCD_1M, TICK_HZ};
 
 #[derive(Debug, Default, Copy, Clone, PartialEq, Eq, PartialOrd, Ord)]
 #[cfg_attr(feature = "defmt", derive(defmt::Format))]
@@ -23,17 +23,17 @@ impl Duration {
 
     /// Convert the `Duration` to seconds, rounding down.
     pub const fn as_secs(&self) -> u64 {
-        self.ticks / TICKS_PER_SECOND
+        self.ticks / TICK_HZ
     }
 
     /// Convert the `Duration` to milliseconds, rounding down.
     pub const fn as_millis(&self) -> u64 {
-        self.ticks * (1000 / GCD_1K) / (TICKS_PER_SECOND / GCD_1K)
+        self.ticks * (1000 / GCD_1K) / (TICK_HZ / GCD_1K)
     }
 
     /// Convert the `Duration` to microseconds, rounding down.
     pub const fn as_micros(&self) -> u64 {
-        self.ticks * (1_000_000 / GCD_1M) / (TICKS_PER_SECOND / GCD_1M)
+        self.ticks * (1_000_000 / GCD_1M) / (TICK_HZ / GCD_1M)
     }
 
     /// Creates a duration from the specified number of clock ticks
@@ -43,15 +43,13 @@ impl Duration {
 
     /// Creates a duration from the specified number of seconds, rounding up.
     pub const fn from_secs(secs: u64) -> Duration {
-        Duration {
-            ticks: secs * TICKS_PER_SECOND,
-        }
+        Duration { ticks: secs * TICK_HZ }
     }
 
     /// Creates a duration from the specified number of milliseconds, rounding up.
     pub const fn from_millis(millis: u64) -> Duration {
         Duration {
-            ticks: div_ceil(millis * (TICKS_PER_SECOND / GCD_1K), 1000 / GCD_1K),
+            ticks: div_ceil(millis * (TICK_HZ / GCD_1K), 1000 / GCD_1K),
         }
     }
 
@@ -59,21 +57,19 @@ impl Duration {
     /// NOTE: Delays this small may be inaccurate.
     pub const fn from_micros(micros: u64) -> Duration {
         Duration {
-            ticks: div_ceil(micros * (TICKS_PER_SECOND / GCD_1M), 1_000_000 / GCD_1M),
+            ticks: div_ceil(micros * (TICK_HZ / GCD_1M), 1_000_000 / GCD_1M),
         }
     }
 
     /// Creates a duration from the specified number of seconds, rounding down.
     pub const fn from_secs_floor(secs: u64) -> Duration {
-        Duration {
-            ticks: secs * TICKS_PER_SECOND,
-        }
+        Duration { ticks: secs * TICK_HZ }
     }
 
     /// Creates a duration from the specified number of milliseconds, rounding down.
     pub const fn from_millis_floor(millis: u64) -> Duration {
         Duration {
-            ticks: millis * (TICKS_PER_SECOND / GCD_1K) / (1000 / GCD_1K),
+            ticks: millis * (TICK_HZ / GCD_1K) / (1000 / GCD_1K),
         }
     }
 
@@ -81,10 +77,24 @@ impl Duration {
     /// NOTE: Delays this small may be inaccurate.
     pub const fn from_micros_floor(micros: u64) -> Duration {
         Duration {
-            ticks: micros * (TICKS_PER_SECOND / GCD_1M) / (1_000_000 / GCD_1M),
+            ticks: micros * (TICK_HZ / GCD_1M) / (1_000_000 / GCD_1M),
         }
     }
 
+    /// Creates a duration corresponding to the specified Hz.
+    /// NOTE: Giving this function a hz >= the TICK_HZ of your platform will clamp the Duration to 1
+    /// tick. Doing so will not deadlock, but will certainly not produce the desired output.
+    pub const fn from_hz(hz: u64) -> Duration {
+        let ticks = {
+            if hz >= TICK_HZ {
+                1
+            } else {
+                (TICK_HZ + hz / 2) / hz
+            }
+        };
+        Duration { ticks }
+    }
+
     /// Adds one Duration to another, returning a new Duration or None in the event of an overflow.
     pub fn checked_add(self, rhs: Duration) -> Option<Duration> {
         self.ticks.checked_add(rhs.ticks).map(|ticks| Duration { ticks })
@@ -182,3 +192,19 @@ impl<'a> fmt::Display for Duration {
 const fn div_ceil(num: u64, den: u64) -> u64 {
     (num + den - 1) / den
 }
+
+impl TryFrom<core::time::Duration> for Duration {
+    type Error = <u64 as TryFrom<u128>>::Error;
+
+    /// Converts using [`Duration::from_micros`]. Fails if value can not be represented as u64.
+    fn try_from(value: core::time::Duration) -> Result<Self, Self::Error> {
+        Ok(Self::from_micros(value.as_micros().try_into()?))
+    }
+}
+
+impl From<Duration> for core::time::Duration {
+    /// Converts using [`Duration::as_micros`].
+    fn from(value: Duration) -> Self {
+        core::time::Duration::from_micros(value.as_micros())
+    }
+}
diff --git a/embassy-time/src/instant.rs b/embassy-time/src/instant.rs
index 6a4925f47..44f226f62 100644
--- a/embassy-time/src/instant.rs
+++ b/embassy-time/src/instant.rs
@@ -1,7 +1,7 @@
 use core::fmt;
 use core::ops::{Add, AddAssign, Sub, SubAssign};
 
-use super::{driver, Duration, GCD_1K, GCD_1M, TICKS_PER_SECOND};
+use super::{driver, Duration, GCD_1K, GCD_1M, TICK_HZ};
 
 #[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord)]
 #[cfg_attr(feature = "defmt", derive(defmt::Format))]
@@ -29,21 +29,21 @@ impl Instant {
     /// Create an Instant from a microsecond count since system boot.
     pub const fn from_micros(micros: u64) -> Self {
         Self {
-            ticks: micros * (TICKS_PER_SECOND / GCD_1M) / (1_000_000 / GCD_1M),
+            ticks: micros * (TICK_HZ / GCD_1M) / (1_000_000 / GCD_1M),
         }
     }
 
     /// Create an Instant from a millisecond count since system boot.
     pub const fn from_millis(millis: u64) -> Self {
         Self {
-            ticks: millis * (TICKS_PER_SECOND / GCD_1K) / (1000 / GCD_1K),
+            ticks: millis * (TICK_HZ / GCD_1K) / (1000 / GCD_1K),
         }
     }
 
     /// Create an Instant from a second count since system boot.
     pub const fn from_secs(seconds: u64) -> Self {
         Self {
-            ticks: seconds * TICKS_PER_SECOND,
+            ticks: seconds * TICK_HZ,
         }
     }
 
@@ -54,17 +54,17 @@ impl Instant {
 
     /// Seconds since system boot.
     pub const fn as_secs(&self) -> u64 {
-        self.ticks / TICKS_PER_SECOND
+        self.ticks / TICK_HZ
     }
 
     /// Milliseconds since system boot.
     pub const fn as_millis(&self) -> u64 {
-        self.ticks * (1000 / GCD_1K) / (TICKS_PER_SECOND / GCD_1K)
+        self.ticks * (1000 / GCD_1K) / (TICK_HZ / GCD_1K)
     }
 
     /// Microseconds since system boot.
     pub const fn as_micros(&self) -> u64 {
-        self.ticks * (1_000_000 / GCD_1M) / (TICKS_PER_SECOND / GCD_1M)
+        self.ticks * (1_000_000 / GCD_1M) / (TICK_HZ / GCD_1M)
     }
 
     /// Duration between this Instant and another Instant
diff --git a/embassy-time/src/lib.rs b/embassy-time/src/lib.rs
index a6c5d78cc..8f57eabcb 100644
--- a/embassy-time/src/lib.rs
+++ b/embassy-time/src/lib.rs
@@ -1,5 +1,5 @@
-#![cfg_attr(not(any(feature = "std", feature = "wasm")), no_std)]
-#![cfg_attr(feature = "nightly", feature(generic_associated_types, type_alias_impl_trait))]
+#![cfg_attr(not(any(feature = "std", feature = "wasm", test)), no_std)]
+#![cfg_attr(feature = "nightly", feature(async_fn_in_trait))]
 #![doc = include_str!("../README.md")]
 #![allow(clippy::new_without_default)]
 #![warn(missing_docs)]
@@ -11,37 +11,29 @@ mod delay;
 pub mod driver;
 mod duration;
 mod instant;
+pub mod queue;
+mod tick;
 mod timer;
 
 #[cfg(feature = "std")]
 mod driver_std;
 #[cfg(feature = "wasm")]
 mod driver_wasm;
+#[cfg(feature = "generic-queue")]
+mod queue_generic;
 
 pub use delay::{block_for, Delay};
 pub use duration::Duration;
 pub use instant::Instant;
 pub use timer::{with_timeout, Ticker, TimeoutError, Timer};
 
-#[cfg(feature = "tick-1000hz")]
-const TPS: u64 = 1_000;
-
-#[cfg(feature = "tick-32768hz")]
-const TPS: u64 = 32_768;
-
-#[cfg(feature = "tick-1mhz")]
-const TPS: u64 = 1_000_000;
-
-#[cfg(feature = "tick-16mhz")]
-const TPS: u64 = 16_000_000;
-
 /// Ticks per second of the global timebase.
 ///
 /// This value is specified by the `tick-*` Cargo features, which
 /// should be set by the time driver. Some drivers support a fixed tick rate, others
 /// allow you to choose a tick rate with Cargo features of their own. You should not
 /// set the `tick-*` features for embassy yourself as an end user.
-pub const TICKS_PER_SECOND: u64 = TPS;
+pub const TICK_HZ: u64 = tick::TICK_HZ;
 
 const fn gcd(a: u64, b: u64) -> u64 {
     if b == 0 {
@@ -51,8 +43,8 @@ const fn gcd(a: u64, b: u64) -> u64 {
     }
 }
 
-pub(crate) const GCD_1K: u64 = gcd(TICKS_PER_SECOND, 1_000);
-pub(crate) const GCD_1M: u64 = gcd(TICKS_PER_SECOND, 1_000_000);
+pub(crate) const GCD_1K: u64 = gcd(TICK_HZ, 1_000);
+pub(crate) const GCD_1M: u64 = gcd(TICK_HZ, 1_000_000);
 
 #[cfg(feature = "defmt-timestamp-uptime")]
 defmt::timestamp! {"{=u64:us}", Instant::now().as_micros() }
diff --git a/embassy-time/src/queue.rs b/embassy-time/src/queue.rs
new file mode 100644
index 000000000..c6f8b440a
--- /dev/null
+++ b/embassy-time/src/queue.rs
@@ -0,0 +1,58 @@
+//! Timer queue implementation
+//!
+//! This module defines the interface a timer queue needs to implement to power the `embassy_time` module.
+//!
+//! # Implementing a timer queue
+//!
+//! - Define a struct `MyTimerQueue`
+//! - Implement [`TimerQueue`] for it
+//! - Register it as the global timer queue with [`timer_queue_impl`](crate::timer_queue_impl).
+//!
+//! # Linkage details
+//!
+//! Check the documentation of the [`driver`](crate::driver) module for more information.
+//!
+//! Similarly to driver, if there is none or multiple timer queues in the crate tree, linking will fail.
+//!
+//! # Example
+//!
+//! ```
+//! use core::task::Waker;
+//!
+//! use embassy_time::Instant;
+//! use embassy_time::queue::{TimerQueue};
+//!
+//! struct MyTimerQueue{}; // not public!
+//! embassy_time::timer_queue_impl!(static QUEUE: MyTimerQueue = MyTimerQueue{});
+//!
+//! impl TimerQueue for MyTimerQueue {
+//!     fn schedule_wake(&'static self, at: Instant, waker: &Waker) {
+//!         todo!()
+//!     }
+//! }
+//! ```
+use core::task::Waker;
+
+use crate::Instant;
+
+/// Timer queue
+pub trait TimerQueue {
+    /// Schedules a waker in the queue to be awoken at moment `at`.
+    /// If this moment is in the past, the waker might be awoken immediately.
+    fn schedule_wake(&'static self, at: Instant, waker: &Waker);
+}
+
+/// Set the TimerQueue implementation.
+///
+/// See the module documentation for an example.
+#[macro_export]
+macro_rules! timer_queue_impl {
+    (static $name:ident: $t: ty = $val:expr) => {
+        static $name: $t = $val;
+
+        #[no_mangle]
+        fn _embassy_time_schedule_wake(at: $crate::Instant, waker: &core::task::Waker) {
+            <$t as $crate::queue::TimerQueue>::schedule_wake(&$name, at, waker);
+        }
+    };
+}
diff --git a/embassy-time/src/queue_generic.rs b/embassy-time/src/queue_generic.rs
new file mode 100644
index 000000000..77947ab29
--- /dev/null
+++ b/embassy-time/src/queue_generic.rs
@@ -0,0 +1,450 @@
+use core::cell::RefCell;
+use core::cmp::{min, Ordering};
+use core::task::Waker;
+
+use critical_section::Mutex;
+use heapless::Vec;
+
+use crate::driver::{allocate_alarm, set_alarm, set_alarm_callback, AlarmHandle};
+use crate::queue::TimerQueue;
+use crate::Instant;
+
+#[cfg(feature = "generic-queue-8")]
+const QUEUE_SIZE: usize = 8;
+#[cfg(feature = "generic-queue-16")]
+const QUEUE_SIZE: usize = 16;
+#[cfg(feature = "generic-queue-32")]
+const QUEUE_SIZE: usize = 32;
+#[cfg(feature = "generic-queue-64")]
+const QUEUE_SIZE: usize = 64;
+#[cfg(feature = "generic-queue-128")]
+const QUEUE_SIZE: usize = 128;
+#[cfg(not(any(
+    feature = "generic-queue-8",
+    feature = "generic-queue-16",
+    feature = "generic-queue-32",
+    feature = "generic-queue-64",
+    feature = "generic-queue-128"
+)))]
+const QUEUE_SIZE: usize = 64;
+
+#[derive(Debug)]
+struct Timer {
+    at: Instant,
+    waker: Waker,
+}
+
+impl PartialEq for Timer {
+    fn eq(&self, other: &Self) -> bool {
+        self.at == other.at
+    }
+}
+
+impl Eq for Timer {}
+
+impl PartialOrd for Timer {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        self.at.partial_cmp(&other.at)
+    }
+}
+
+impl Ord for Timer {
+    fn cmp(&self, other: &Self) -> Ordering {
+        self.at.cmp(&other.at)
+    }
+}
+
+struct InnerQueue {
+    queue: Vec<Timer, QUEUE_SIZE>,
+    alarm: AlarmHandle,
+}
+
+impl InnerQueue {
+    fn schedule_wake(&mut self, at: Instant, waker: &Waker) {
+        self.queue
+            .iter_mut()
+            .find(|timer| timer.waker.will_wake(waker))
+            .map(|timer| {
+                timer.at = min(timer.at, at);
+            })
+            .unwrap_or_else(|| {
+                let mut timer = Timer {
+                    waker: waker.clone(),
+                    at,
+                };
+
+                loop {
+                    match self.queue.push(timer) {
+                        Ok(()) => break,
+                        Err(e) => timer = e,
+                    }
+
+                    self.queue.pop().unwrap().waker.wake();
+                }
+            });
+
+        // Don't wait for the alarm callback to trigger and directly
+        // dispatch all timers that are already due
+        //
+        // Then update the alarm if necessary
+        self.dispatch();
+    }
+
+    fn dispatch(&mut self) {
+        loop {
+            let now = Instant::now();
+
+            let mut next_alarm = Instant::MAX;
+
+            let mut i = 0;
+            while i < self.queue.len() {
+                let timer = &self.queue[i];
+                if timer.at <= now {
+                    let timer = self.queue.swap_remove(i);
+                    timer.waker.wake();
+                } else {
+                    next_alarm = min(next_alarm, timer.at);
+                    i += 1;
+                }
+            }
+
+            if self.update_alarm(next_alarm) {
+                break;
+            }
+        }
+    }
+
+    fn update_alarm(&mut self, next_alarm: Instant) -> bool {
+        if next_alarm == Instant::MAX {
+            true
+        } else {
+            set_alarm(self.alarm, next_alarm.as_ticks())
+        }
+    }
+
+    fn handle_alarm(&mut self) {
+        self.dispatch();
+    }
+}
+
+struct Queue {
+    inner: Mutex<RefCell<Option<InnerQueue>>>,
+}
+
+impl Queue {
+    const fn new() -> Self {
+        Self {
+            inner: Mutex::new(RefCell::new(None)),
+        }
+    }
+
+    fn schedule_wake(&'static self, at: Instant, waker: &Waker) {
+        critical_section::with(|cs| {
+            let mut inner = self.inner.borrow_ref_mut(cs);
+
+            if inner.is_none() {}
+
+            inner
+                .get_or_insert_with(|| {
+                    let handle = unsafe { allocate_alarm() }.unwrap();
+                    set_alarm_callback(handle, Self::handle_alarm_callback, self as *const _ as _);
+                    InnerQueue {
+                        queue: Vec::new(),
+                        alarm: handle,
+                    }
+                })
+                .schedule_wake(at, waker)
+        });
+    }
+
+    fn handle_alarm(&self) {
+        critical_section::with(|cs| self.inner.borrow_ref_mut(cs).as_mut().unwrap().handle_alarm())
+    }
+
+    fn handle_alarm_callback(ctx: *mut ()) {
+        unsafe { (ctx as *const Self).as_ref().unwrap() }.handle_alarm();
+    }
+}
+
+impl TimerQueue for Queue {
+    fn schedule_wake(&'static self, at: Instant, waker: &Waker) {
+        Queue::schedule_wake(self, at, waker);
+    }
+}
+
+crate::timer_queue_impl!(static QUEUE: Queue = Queue::new());
+
+#[cfg(test)]
+mod tests {
+    use core::cell::Cell;
+    use core::task::{RawWaker, RawWakerVTable, Waker};
+    use std::rc::Rc;
+    use std::sync::Mutex;
+
+    use serial_test::serial;
+
+    use crate::driver::{AlarmHandle, Driver};
+    use crate::queue_generic::QUEUE;
+    use crate::Instant;
+
+    struct InnerTestDriver {
+        now: u64,
+        alarm: u64,
+        callback: fn(*mut ()),
+        ctx: *mut (),
+    }
+
+    impl InnerTestDriver {
+        const fn new() -> Self {
+            Self {
+                now: 0,
+                alarm: u64::MAX,
+                callback: Self::noop,
+                ctx: core::ptr::null_mut(),
+            }
+        }
+
+        fn noop(_ctx: *mut ()) {}
+    }
+
+    unsafe impl Send for InnerTestDriver {}
+
+    struct TestDriver(Mutex<InnerTestDriver>);
+
+    impl TestDriver {
+        const fn new() -> Self {
+            Self(Mutex::new(InnerTestDriver::new()))
+        }
+
+        fn reset(&self) {
+            *self.0.lock().unwrap() = InnerTestDriver::new();
+        }
+
+        fn set_now(&self, now: u64) {
+            let notify = {
+                let mut inner = self.0.lock().unwrap();
+
+                if inner.now < now {
+                    inner.now = now;
+
+                    if inner.alarm <= now {
+                        inner.alarm = u64::MAX;
+
+                        Some((inner.callback, inner.ctx))
+                    } else {
+                        None
+                    }
+                } else {
+                    panic!("Going back in time?");
+                }
+            };
+
+            if let Some((callback, ctx)) = notify {
+                (callback)(ctx);
+            }
+        }
+    }
+
+    impl Driver for TestDriver {
+        fn now(&self) -> u64 {
+            self.0.lock().unwrap().now
+        }
+
+        unsafe fn allocate_alarm(&self) -> Option<AlarmHandle> {
+            Some(AlarmHandle::new(0))
+        }
+
+        fn set_alarm_callback(&self, _alarm: AlarmHandle, callback: fn(*mut ()), ctx: *mut ()) {
+            let mut inner = self.0.lock().unwrap();
+
+            inner.callback = callback;
+            inner.ctx = ctx;
+        }
+
+        fn set_alarm(&self, _alarm: AlarmHandle, timestamp: u64) -> bool {
+            let mut inner = self.0.lock().unwrap();
+
+            if timestamp <= inner.now {
+                false
+            } else {
+                inner.alarm = timestamp;
+                true
+            }
+        }
+    }
+
+    struct TestWaker {
+        pub awoken: Rc<Cell<bool>>,
+        pub waker: Waker,
+    }
+
+    impl TestWaker {
+        fn new() -> Self {
+            let flag = Rc::new(Cell::new(false));
+
+            const VTABLE: RawWakerVTable = RawWakerVTable::new(
+                |data: *const ()| {
+                    unsafe {
+                        Rc::increment_strong_count(data as *const Cell<bool>);
+                    }
+
+                    RawWaker::new(data as _, &VTABLE)
+                },
+                |data: *const ()| unsafe {
+                    let data = data as *const Cell<bool>;
+                    data.as_ref().unwrap().set(true);
+                    Rc::decrement_strong_count(data);
+                },
+                |data: *const ()| unsafe {
+                    (data as *const Cell<bool>).as_ref().unwrap().set(true);
+                },
+                |data: *const ()| unsafe {
+                    Rc::decrement_strong_count(data);
+                },
+            );
+
+            let raw = RawWaker::new(Rc::into_raw(flag.clone()) as _, &VTABLE);
+
+            Self {
+                awoken: flag.clone(),
+                waker: unsafe { Waker::from_raw(raw) },
+            }
+        }
+    }
+
+    crate::time_driver_impl!(static DRIVER: TestDriver = TestDriver::new());
+
+    fn setup() {
+        DRIVER.reset();
+        critical_section::with(|cs| *QUEUE.inner.borrow_ref_mut(cs) = None);
+    }
+
+    fn queue_len() -> usize {
+        critical_section::with(|cs| {
+            QUEUE
+                .inner
+                .borrow_ref(cs)
+                .as_ref()
+                .map(|inner| inner.queue.iter().count())
+                .unwrap_or(0)
+        })
+    }
+
+    #[test]
+    #[serial]
+    fn test_schedule() {
+        setup();
+
+        assert_eq!(queue_len(), 0);
+
+        let waker = TestWaker::new();
+
+        QUEUE.schedule_wake(Instant::from_secs(1), &waker.waker);
+
+        assert!(!waker.awoken.get());
+        assert_eq!(queue_len(), 1);
+    }
+
+    #[test]
+    #[serial]
+    fn test_schedule_same() {
+        setup();
+
+        let waker = TestWaker::new();
+
+        QUEUE.schedule_wake(Instant::from_secs(1), &waker.waker);
+
+        assert_eq!(queue_len(), 1);
+
+        QUEUE.schedule_wake(Instant::from_secs(1), &waker.waker);
+
+        assert_eq!(queue_len(), 1);
+
+        QUEUE.schedule_wake(Instant::from_secs(100), &waker.waker);
+
+        assert_eq!(queue_len(), 1);
+
+        let waker2 = TestWaker::new();
+
+        QUEUE.schedule_wake(Instant::from_secs(100), &waker2.waker);
+
+        assert_eq!(queue_len(), 2);
+    }
+
+    #[test]
+    #[serial]
+    fn test_trigger() {
+        setup();
+
+        let waker = TestWaker::new();
+
+        QUEUE.schedule_wake(Instant::from_secs(100), &waker.waker);
+
+        assert!(!waker.awoken.get());
+
+        DRIVER.set_now(Instant::from_secs(99).as_ticks());
+
+        assert!(!waker.awoken.get());
+
+        assert_eq!(queue_len(), 1);
+
+        DRIVER.set_now(Instant::from_secs(100).as_ticks());
+
+        assert!(waker.awoken.get());
+
+        assert_eq!(queue_len(), 0);
+    }
+
+    #[test]
+    #[serial]
+    fn test_immediate_trigger() {
+        setup();
+
+        let waker = TestWaker::new();
+
+        QUEUE.schedule_wake(Instant::from_secs(100), &waker.waker);
+
+        DRIVER.set_now(Instant::from_secs(50).as_ticks());
+
+        let waker2 = TestWaker::new();
+
+        QUEUE.schedule_wake(Instant::from_secs(40), &waker2.waker);
+
+        assert!(!waker.awoken.get());
+        assert!(waker2.awoken.get());
+        assert_eq!(queue_len(), 1);
+    }
+
+    #[test]
+    #[serial]
+    fn test_queue_overflow() {
+        setup();
+
+        for i in 1..super::QUEUE_SIZE {
+            let waker = TestWaker::new();
+
+            QUEUE.schedule_wake(Instant::from_secs(310), &waker.waker);
+
+            assert_eq!(queue_len(), i);
+            assert!(!waker.awoken.get());
+        }
+
+        let first_waker = TestWaker::new();
+
+        QUEUE.schedule_wake(Instant::from_secs(300), &first_waker.waker);
+
+        assert_eq!(queue_len(), super::QUEUE_SIZE);
+        assert!(!first_waker.awoken.get());
+
+        let second_waker = TestWaker::new();
+
+        QUEUE.schedule_wake(Instant::from_secs(305), &second_waker.waker);
+
+        assert_eq!(queue_len(), super::QUEUE_SIZE);
+        assert!(first_waker.awoken.get());
+
+        QUEUE.schedule_wake(Instant::from_secs(320), &TestWaker::new().waker);
+        assert_eq!(queue_len(), super::QUEUE_SIZE);
+        assert!(second_waker.awoken.get());
+    }
+}
diff --git a/embassy-time/src/tick.rs b/embassy-time/src/tick.rs
new file mode 100644
index 000000000..608bc44f1
--- /dev/null
+++ b/embassy-time/src/tick.rs
@@ -0,0 +1,239 @@
+// Generated by gen_tick.py. DO NOT EDIT.
+
+#[cfg(feature = "tick-hz-1")]
+pub const TICK_HZ: u64 = 1;
+#[cfg(feature = "tick-hz-10")]
+pub const TICK_HZ: u64 = 10;
+#[cfg(feature = "tick-hz-100")]
+pub const TICK_HZ: u64 = 100;
+#[cfg(feature = "tick-hz-1_000")]
+pub const TICK_HZ: u64 = 1_000;
+#[cfg(feature = "tick-hz-10_000")]
+pub const TICK_HZ: u64 = 10_000;
+#[cfg(feature = "tick-hz-100_000")]
+pub const TICK_HZ: u64 = 100_000;
+#[cfg(feature = "tick-hz-1_000_000")]
+pub const TICK_HZ: u64 = 1_000_000;
+#[cfg(feature = "tick-hz-10_000_000")]
+pub const TICK_HZ: u64 = 10_000_000;
+#[cfg(feature = "tick-hz-100_000_000")]
+pub const TICK_HZ: u64 = 100_000_000;
+#[cfg(feature = "tick-hz-1_000_000_000")]
+pub const TICK_HZ: u64 = 1_000_000_000;
+#[cfg(feature = "tick-hz-2")]
+pub const TICK_HZ: u64 = 2;
+#[cfg(feature = "tick-hz-4")]
+pub const TICK_HZ: u64 = 4;
+#[cfg(feature = "tick-hz-8")]
+pub const TICK_HZ: u64 = 8;
+#[cfg(feature = "tick-hz-16")]
+pub const TICK_HZ: u64 = 16;
+#[cfg(feature = "tick-hz-32")]
+pub const TICK_HZ: u64 = 32;
+#[cfg(feature = "tick-hz-64")]
+pub const TICK_HZ: u64 = 64;
+#[cfg(feature = "tick-hz-128")]
+pub const TICK_HZ: u64 = 128;
+#[cfg(feature = "tick-hz-256")]
+pub const TICK_HZ: u64 = 256;
+#[cfg(feature = "tick-hz-512")]
+pub const TICK_HZ: u64 = 512;
+#[cfg(feature = "tick-hz-1_024")]
+pub const TICK_HZ: u64 = 1_024;
+#[cfg(feature = "tick-hz-2_048")]
+pub const TICK_HZ: u64 = 2_048;
+#[cfg(feature = "tick-hz-4_096")]
+pub const TICK_HZ: u64 = 4_096;
+#[cfg(feature = "tick-hz-8_192")]
+pub const TICK_HZ: u64 = 8_192;
+#[cfg(feature = "tick-hz-16_384")]
+pub const TICK_HZ: u64 = 16_384;
+#[cfg(feature = "tick-hz-32_768")]
+pub const TICK_HZ: u64 = 32_768;
+#[cfg(feature = "tick-hz-65_536")]
+pub const TICK_HZ: u64 = 65_536;
+#[cfg(feature = "tick-hz-131_072")]
+pub const TICK_HZ: u64 = 131_072;
+#[cfg(feature = "tick-hz-262_144")]
+pub const TICK_HZ: u64 = 262_144;
+#[cfg(feature = "tick-hz-524_288")]
+pub const TICK_HZ: u64 = 524_288;
+#[cfg(feature = "tick-hz-1_048_576")]
+pub const TICK_HZ: u64 = 1_048_576;
+#[cfg(feature = "tick-hz-2_097_152")]
+pub const TICK_HZ: u64 = 2_097_152;
+#[cfg(feature = "tick-hz-4_194_304")]
+pub const TICK_HZ: u64 = 4_194_304;
+#[cfg(feature = "tick-hz-8_388_608")]
+pub const TICK_HZ: u64 = 8_388_608;
+#[cfg(feature = "tick-hz-16_777_216")]
+pub const TICK_HZ: u64 = 16_777_216;
+#[cfg(feature = "tick-hz-2_000")]
+pub const TICK_HZ: u64 = 2_000;
+#[cfg(feature = "tick-hz-4_000")]
+pub const TICK_HZ: u64 = 4_000;
+#[cfg(feature = "tick-hz-8_000")]
+pub const TICK_HZ: u64 = 8_000;
+#[cfg(feature = "tick-hz-16_000")]
+pub const TICK_HZ: u64 = 16_000;
+#[cfg(feature = "tick-hz-32_000")]
+pub const TICK_HZ: u64 = 32_000;
+#[cfg(feature = "tick-hz-64_000")]
+pub const TICK_HZ: u64 = 64_000;
+#[cfg(feature = "tick-hz-128_000")]
+pub const TICK_HZ: u64 = 128_000;
+#[cfg(feature = "tick-hz-256_000")]
+pub const TICK_HZ: u64 = 256_000;
+#[cfg(feature = "tick-hz-512_000")]
+pub const TICK_HZ: u64 = 512_000;
+#[cfg(feature = "tick-hz-1_024_000")]
+pub const TICK_HZ: u64 = 1_024_000;
+#[cfg(feature = "tick-hz-2_048_000")]
+pub const TICK_HZ: u64 = 2_048_000;
+#[cfg(feature = "tick-hz-4_096_000")]
+pub const TICK_HZ: u64 = 4_096_000;
+#[cfg(feature = "tick-hz-8_192_000")]
+pub const TICK_HZ: u64 = 8_192_000;
+#[cfg(feature = "tick-hz-16_384_000")]
+pub const TICK_HZ: u64 = 16_384_000;
+#[cfg(feature = "tick-hz-32_768_000")]
+pub const TICK_HZ: u64 = 32_768_000;
+#[cfg(feature = "tick-hz-65_536_000")]
+pub const TICK_HZ: u64 = 65_536_000;
+#[cfg(feature = "tick-hz-131_072_000")]
+pub const TICK_HZ: u64 = 131_072_000;
+#[cfg(feature = "tick-hz-262_144_000")]
+pub const TICK_HZ: u64 = 262_144_000;
+#[cfg(feature = "tick-hz-524_288_000")]
+pub const TICK_HZ: u64 = 524_288_000;
+#[cfg(feature = "tick-hz-2_000_000")]
+pub const TICK_HZ: u64 = 2_000_000;
+#[cfg(feature = "tick-hz-3_000_000")]
+pub const TICK_HZ: u64 = 3_000_000;
+#[cfg(feature = "tick-hz-4_000_000")]
+pub const TICK_HZ: u64 = 4_000_000;
+#[cfg(feature = "tick-hz-6_000_000")]
+pub const TICK_HZ: u64 = 6_000_000;
+#[cfg(feature = "tick-hz-8_000_000")]
+pub const TICK_HZ: u64 = 8_000_000;
+#[cfg(feature = "tick-hz-9_000_000")]
+pub const TICK_HZ: u64 = 9_000_000;
+#[cfg(feature = "tick-hz-12_000_000")]
+pub const TICK_HZ: u64 = 12_000_000;
+#[cfg(feature = "tick-hz-16_000_000")]
+pub const TICK_HZ: u64 = 16_000_000;
+#[cfg(feature = "tick-hz-18_000_000")]
+pub const TICK_HZ: u64 = 18_000_000;
+#[cfg(feature = "tick-hz-24_000_000")]
+pub const TICK_HZ: u64 = 24_000_000;
+#[cfg(feature = "tick-hz-32_000_000")]
+pub const TICK_HZ: u64 = 32_000_000;
+#[cfg(feature = "tick-hz-36_000_000")]
+pub const TICK_HZ: u64 = 36_000_000;
+#[cfg(feature = "tick-hz-48_000_000")]
+pub const TICK_HZ: u64 = 48_000_000;
+#[cfg(feature = "tick-hz-64_000_000")]
+pub const TICK_HZ: u64 = 64_000_000;
+#[cfg(feature = "tick-hz-72_000_000")]
+pub const TICK_HZ: u64 = 72_000_000;
+#[cfg(feature = "tick-hz-96_000_000")]
+pub const TICK_HZ: u64 = 96_000_000;
+#[cfg(feature = "tick-hz-128_000_000")]
+pub const TICK_HZ: u64 = 128_000_000;
+#[cfg(feature = "tick-hz-144_000_000")]
+pub const TICK_HZ: u64 = 144_000_000;
+#[cfg(feature = "tick-hz-192_000_000")]
+pub const TICK_HZ: u64 = 192_000_000;
+#[cfg(feature = "tick-hz-256_000_000")]
+pub const TICK_HZ: u64 = 256_000_000;
+#[cfg(feature = "tick-hz-288_000_000")]
+pub const TICK_HZ: u64 = 288_000_000;
+#[cfg(feature = "tick-hz-384_000_000")]
+pub const TICK_HZ: u64 = 384_000_000;
+#[cfg(feature = "tick-hz-512_000_000")]
+pub const TICK_HZ: u64 = 512_000_000;
+#[cfg(feature = "tick-hz-576_000_000")]
+pub const TICK_HZ: u64 = 576_000_000;
+#[cfg(feature = "tick-hz-768_000_000")]
+pub const TICK_HZ: u64 = 768_000_000;
+#[cfg(not(any(
+    feature = "tick-hz-1",
+    feature = "tick-hz-10",
+    feature = "tick-hz-100",
+    feature = "tick-hz-1_000",
+    feature = "tick-hz-10_000",
+    feature = "tick-hz-100_000",
+    feature = "tick-hz-1_000_000",
+    feature = "tick-hz-10_000_000",
+    feature = "tick-hz-100_000_000",
+    feature = "tick-hz-1_000_000_000",
+    feature = "tick-hz-2",
+    feature = "tick-hz-4",
+    feature = "tick-hz-8",
+    feature = "tick-hz-16",
+    feature = "tick-hz-32",
+    feature = "tick-hz-64",
+    feature = "tick-hz-128",
+    feature = "tick-hz-256",
+    feature = "tick-hz-512",
+    feature = "tick-hz-1_024",
+    feature = "tick-hz-2_048",
+    feature = "tick-hz-4_096",
+    feature = "tick-hz-8_192",
+    feature = "tick-hz-16_384",
+    feature = "tick-hz-32_768",
+    feature = "tick-hz-65_536",
+    feature = "tick-hz-131_072",
+    feature = "tick-hz-262_144",
+    feature = "tick-hz-524_288",
+    feature = "tick-hz-1_048_576",
+    feature = "tick-hz-2_097_152",
+    feature = "tick-hz-4_194_304",
+    feature = "tick-hz-8_388_608",
+    feature = "tick-hz-16_777_216",
+    feature = "tick-hz-2_000",
+    feature = "tick-hz-4_000",
+    feature = "tick-hz-8_000",
+    feature = "tick-hz-16_000",
+    feature = "tick-hz-32_000",
+    feature = "tick-hz-64_000",
+    feature = "tick-hz-128_000",
+    feature = "tick-hz-256_000",
+    feature = "tick-hz-512_000",
+    feature = "tick-hz-1_024_000",
+    feature = "tick-hz-2_048_000",
+    feature = "tick-hz-4_096_000",
+    feature = "tick-hz-8_192_000",
+    feature = "tick-hz-16_384_000",
+    feature = "tick-hz-32_768_000",
+    feature = "tick-hz-65_536_000",
+    feature = "tick-hz-131_072_000",
+    feature = "tick-hz-262_144_000",
+    feature = "tick-hz-524_288_000",
+    feature = "tick-hz-2_000_000",
+    feature = "tick-hz-3_000_000",
+    feature = "tick-hz-4_000_000",
+    feature = "tick-hz-6_000_000",
+    feature = "tick-hz-8_000_000",
+    feature = "tick-hz-9_000_000",
+    feature = "tick-hz-12_000_000",
+    feature = "tick-hz-16_000_000",
+    feature = "tick-hz-18_000_000",
+    feature = "tick-hz-24_000_000",
+    feature = "tick-hz-32_000_000",
+    feature = "tick-hz-36_000_000",
+    feature = "tick-hz-48_000_000",
+    feature = "tick-hz-64_000_000",
+    feature = "tick-hz-72_000_000",
+    feature = "tick-hz-96_000_000",
+    feature = "tick-hz-128_000_000",
+    feature = "tick-hz-144_000_000",
+    feature = "tick-hz-192_000_000",
+    feature = "tick-hz-256_000_000",
+    feature = "tick-hz-288_000_000",
+    feature = "tick-hz-384_000_000",
+    feature = "tick-hz-512_000_000",
+    feature = "tick-hz-576_000_000",
+    feature = "tick-hz-768_000_000",
+)))]
+pub const TICK_HZ: u64 = 1_000_000;
diff --git a/embassy-time/src/timer.rs b/embassy-time/src/timer.rs
index bd791b817..d3d1f9f5f 100644
--- a/embassy-time/src/timer.rs
+++ b/embassy-time/src/timer.rs
@@ -1,4 +1,4 @@
-use core::future::Future;
+use core::future::{poll_fn, Future};
 use core::pin::Pin;
 use core::task::{Context, Poll, Waker};
 
@@ -26,6 +26,7 @@ pub async fn with_timeout<F: Future>(timeout: Duration, fut: F) -> Result<F::Out
 }
 
 /// A future that completes at a specified [Instant](struct.Instant.html).
+#[must_use = "futures do nothing unless you `.await` or poll them"]
 pub struct Timer {
     expires_at: Instant,
     yielded_once: bool,
@@ -108,7 +109,6 @@ impl Future for Timer {
 /// # #![feature(type_alias_impl_trait)]
 /// #
 /// use embassy_time::{Duration, Ticker};
-/// use futures::StreamExt;
 /// # fn foo(){}
 ///
 /// #[embassy_executor::task]
@@ -131,6 +131,20 @@ impl Ticker {
         let expires_at = Instant::now() + duration;
         Self { expires_at, duration }
     }
+
+    /// Waits for the next tick
+    pub fn next(&mut self) -> impl Future<Output = ()> + '_ {
+        poll_fn(|cx| {
+            if self.expires_at <= Instant::now() {
+                let dur = self.duration;
+                self.expires_at += dur;
+                Poll::Ready(())
+            } else {
+                schedule_wake(self.expires_at, cx.waker());
+                Poll::Pending
+            }
+        })
+    }
 }
 
 impl Unpin for Ticker {}