Add clock::Monotonic trait.

embassy/Cargo.toml

@@ -12,3 +12,4 @@ defmt = "0.1.0"
 cortex-m = "0.6.3"
 futures     = { version = "0.3.5", default-features = false, features = [ "async-await" ] }
 pin-project = { version = "0.4.23", default-features = false }
+futures-intrusive = { version = "0.3.1", default-features = false }

embassy/src/clock.rs

@@ -0,0 +1,21 @@
+/// Monotonic clock with support for setting an alarm.
+///
+/// The clock uses a "tick" time unit, whose length is an implementation-dependent constant.
+pub trait Monotonic {
+    /// Returns the current timestamp in ticks.
+    /// This is guaranteed to be monotonic, i.e. a call to now() will always return
+    /// a greater or equal value than earler calls.
+    fn now(&self) -> u64;
+
+    /// Sets an alarm at the given timestamp. When the clock reaches that
+    /// timestamp, the provided callback funcion will be called.
+    ///
+    /// 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. This overwrites any previously-set alarm if any.
+    fn set_alarm(&self, timestamp: u64, callback: fn());
+
+    /// Clears the previously-set alarm.
+    /// If no alarm was set, this is a noop.
+    fn clear_alarm(&self);
+}

embassy/src/lib.rs

@@ -3,6 +3,7 @@
 #![feature(generic_associated_types)]
 #![feature(const_fn)]
 
+pub mod clock;
 pub mod flash;
-pub mod util;
 pub mod io;
+pub mod util;