Merge #695

695: Simplify Channel. r=Dirbaio a=Dirbaio

- Allow initializing in a static, without Forever.
- Remove ability to close, since in embedded enviromnents channels usually live forever and don't get closed.
- Remove MPSC restriction, it's MPMC now. Rename "mpsc" to "channel".
- `Sender` and `Receiver` are still available if you want to enforce a piece of code only has send/receive access, but are optional: you can send/receive directly into the Channel if you want.

Co-authored-by: Dario Nieuwenhuis <[email protected]>

10 files changed, 571 insertions, 950 deletions

diff --git a/embassy/src/channel/channel.rs b/embassy/src/channel/channel.rs
new file mode 100644
index 000000000..9084cd57b
--- /dev/null
+++ b/embassy/src/channel/channel.rs
@@ -0,0 +1,430 @@
+//! A queue for sending values between asynchronous tasks.
+//!
+//! It can be used concurrently by multiple producers (senders) and multiple
+//! consumers (receivers), i.e. it is an  "MPMC channel".
+//!
+//! This queue takes a Mutex type so that various
+//! targets can be attained. For example, a ThreadModeMutex can be used
+//! for single-core Cortex-M targets where messages are only passed
+//! between tasks running in thread mode. Similarly, a CriticalSectionMutex
+//! can also be used for single-core targets where messages are to be
+//! passed from exception mode e.g. out of an interrupt handler.
+//!
+//! This module provides a bounded channel that has a limit on the number of
+//! messages that it can store, and if this limit is reached, trying to send
+//! another message will result in an error being returned.
+//!
+
+use core::cell::RefCell;
+use core::pin::Pin;
+use core::task::Context;
+use core::task::Poll;
+
+use futures::Future;
+use heapless::Deque;
+
+use crate::blocking_mutex::raw::RawMutex;
+use crate::blocking_mutex::Mutex;
+use crate::waitqueue::WakerRegistration;
+
+/// Send-only access to a [`Channel`].
+#[derive(Copy, Clone)]
+pub struct Sender<'ch, M, T, const N: usize>
+where
+    M: RawMutex,
+{
+    channel: &'ch Channel<M, T, N>,
+}
+
+impl<'ch, M, T, const N: usize> Sender<'ch, M, T, N>
+where
+    M: RawMutex,
+{
+    /// Sends a value.
+    ///
+    /// See [`Channel::send()`]
+    pub fn send(&self, message: T) -> SendFuture<'ch, M, T, N> {
+        self.channel.send(message)
+    }
+
+    /// Attempt to immediately send a message.
+    ///
+    /// See [`Channel::send()`]
+    pub fn try_send(&self, message: T) -> Result<(), TrySendError<T>> {
+        self.channel.try_send(message)
+    }
+}
+
+/// Receive-only access to a [`Channel`].
+#[derive(Copy, Clone)]
+pub struct Receiver<'ch, M, T, const N: usize>
+where
+    M: RawMutex,
+{
+    channel: &'ch Channel<M, T, N>,
+}
+
+impl<'ch, M, T, const N: usize> Receiver<'ch, M, T, N>
+where
+    M: RawMutex,
+{
+    /// Receive the next value.
+    ///
+    /// See [`Channel::recv()`].
+    pub fn recv(&self) -> RecvFuture<'_, M, T, N> {
+        self.channel.recv()
+    }
+
+    /// Attempt to immediately receive the next value.
+    ///
+    /// See [`Channel::try_recv()`]
+    pub fn try_recv(&self) -> Result<T, TryRecvError> {
+        self.channel.try_recv()
+    }
+}
+
+pub struct RecvFuture<'ch, M, T, const N: usize>
+where
+    M: RawMutex,
+{
+    channel: &'ch Channel<M, T, N>,
+}
+
+impl<'ch, M, T, const N: usize> Future for RecvFuture<'ch, M, T, N>
+where
+    M: RawMutex,
+{
+    type Output = T;
+
+    fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<T> {
+        self.channel
+            .lock(|c| match c.try_recv_with_context(Some(cx)) {
+                Ok(v) => Poll::Ready(v),
+                Err(TryRecvError::Empty) => Poll::Pending,
+            })
+    }
+}
+
+pub struct SendFuture<'ch, M, T, const N: usize>
+where
+    M: RawMutex,
+{
+    channel: &'ch Channel<M, T, N>,
+    message: Option<T>,
+}
+
+impl<'ch, M, T, const N: usize> Future for SendFuture<'ch, M, T, N>
+where
+    M: RawMutex,
+{
+    type Output = ();
+
+    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+        match self.message.take() {
+            Some(m) => match self.channel.lock(|c| c.try_send_with_context(m, Some(cx))) {
+                Ok(..) => Poll::Ready(()),
+                Err(TrySendError::Full(m)) => {
+                    self.message = Some(m);
+                    Poll::Pending
+                }
+            },
+            None => panic!("Message cannot be None"),
+        }
+    }
+}
+
+impl<'ch, M, T, const N: usize> Unpin for SendFuture<'ch, M, T, N> where M: RawMutex {}
+
+/// Error returned by [`try_recv`](Channel::try_recv).
+#[derive(PartialEq, Eq, Clone, Copy, Debug)]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+pub enum TryRecvError {
+    /// A message could not be received because the channel is empty.
+    Empty,
+}
+
+/// Error returned by [`try_send`](Channel::try_send).
+#[derive(PartialEq, Eq, Clone, Copy, Debug)]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+pub enum TrySendError<T> {
+    /// The data could not be sent on the channel because the channel is
+    /// currently full and sending would require blocking.
+    Full(T),
+}
+
+struct ChannelState<T, const N: usize> {
+    queue: Deque<T, N>,
+    receiver_waker: WakerRegistration,
+    senders_waker: WakerRegistration,
+}
+
+impl<T, const N: usize> ChannelState<T, N> {
+    const fn new() -> Self {
+        ChannelState {
+            queue: Deque::new(),
+            receiver_waker: WakerRegistration::new(),
+            senders_waker: WakerRegistration::new(),
+        }
+    }
+
+    fn try_recv(&mut self) -> Result<T, TryRecvError> {
+        self.try_recv_with_context(None)
+    }
+
+    fn try_recv_with_context(&mut self, cx: Option<&mut Context<'_>>) -> Result<T, TryRecvError> {
+        if self.queue.is_full() {
+            self.senders_waker.wake();
+        }
+
+        if let Some(message) = self.queue.pop_front() {
+            Ok(message)
+        } else {
+            if let Some(cx) = cx {
+                self.receiver_waker.register(cx.waker());
+            }
+            Err(TryRecvError::Empty)
+        }
+    }
+
+    fn try_send(&mut self, message: T) -> Result<(), TrySendError<T>> {
+        self.try_send_with_context(message, None)
+    }
+
+    fn try_send_with_context(
+        &mut self,
+        message: T,
+        cx: Option<&mut Context<'_>>,
+    ) -> Result<(), TrySendError<T>> {
+        match self.queue.push_back(message) {
+            Ok(()) => {
+                self.receiver_waker.wake();
+                Ok(())
+            }
+            Err(message) => {
+                if let Some(cx) = cx {
+                    self.senders_waker.register(cx.waker());
+                }
+                Err(TrySendError::Full(message))
+            }
+        }
+    }
+}
+
+/// A bounded channel for communicating between asynchronous tasks
+/// with backpressure.
+///
+/// The channel will buffer up to the provided number of messages.  Once the
+/// buffer is full, attempts to `send` new messages will wait until a message is
+/// received from the channel.
+///
+/// All data sent will become available in the same order as it was sent.
+pub struct Channel<M, T, const N: usize>
+where
+    M: RawMutex,
+{
+    inner: Mutex<M, RefCell<ChannelState<T, N>>>,
+}
+
+impl<M, T, const N: usize> Channel<M, T, N>
+where
+    M: RawMutex,
+{
+    /// Establish a new bounded channel. For example, to create one with a NoopMutex:
+    ///
+    /// ```
+    /// use embassy::channel::channel::Channel;
+    /// use embassy::blocking_mutex::raw::NoopRawMutex;
+    ///
+    /// // Declare a bounded channel of 3 u32s.
+    /// let mut channel = Channel::<NoopRawMutex, u32, 3>::new();
+    /// ```
+    #[cfg(feature = "nightly")]
+    pub const fn new() -> Self {
+        Self {
+            inner: Mutex::new(RefCell::new(ChannelState::new())),
+        }
+    }
+
+    /// Establish a new bounded channel. For example, to create one with a NoopMutex:
+    ///
+    /// ```
+    /// use embassy::channel::channel::Channel;
+    /// use embassy::blocking_mutex::raw::NoopRawMutex;
+    ///
+    /// // Declare a bounded channel of 3 u32s.
+    /// let mut channel = Channel::<NoopRawMutex, u32, 3>::new();
+    /// ```
+    #[cfg(not(feature = "nightly"))]
+    pub fn new() -> Self {
+        Self {
+            inner: Mutex::new(RefCell::new(ChannelState::new())),
+        }
+    }
+
+    fn lock<R>(&self, f: impl FnOnce(&mut ChannelState<T, N>) -> R) -> R {
+        self.inner.lock(|rc| f(&mut *rc.borrow_mut()))
+    }
+
+    /// Get a sender for this channel.
+    pub fn sender(&self) -> Sender<'_, M, T, N> {
+        Sender { channel: self }
+    }
+
+    /// Get a receiver for this channel.
+    pub fn receiver(&self) -> Receiver<'_, M, T, N> {
+        Receiver { channel: self }
+    }
+
+    /// Send a value, waiting until there is capacity.
+    ///
+    /// Sending completes when the value has been pushed to the channel's queue.
+    /// This doesn't mean the value has been received yet.
+    pub fn send(&self, message: T) -> SendFuture<'_, M, T, N> {
+        SendFuture {
+            channel: self,
+            message: Some(message),
+        }
+    }
+
+    /// Attempt to immediately send a message.
+    ///
+    /// This method differs from [`send`] by returning immediately if the channel's
+    /// buffer is full, instead of waiting.
+    ///
+    /// # Errors
+    ///
+    /// If the channel capacity has been reached, i.e., the channel has `n`
+    /// buffered values where `n` is the argument passed to [`Channel`], then an
+    /// error is returned.
+    pub fn try_send(&self, message: T) -> Result<(), TrySendError<T>> {
+        self.lock(|c| c.try_send(message))
+    }
+
+    /// Receive the next value.
+    ///
+    /// If there are no messages in the channel's buffer, this method will
+    /// wait until a message is sent.
+    pub fn recv(&self) -> RecvFuture<'_, M, T, N> {
+        RecvFuture { channel: self }
+    }
+
+    /// Attempt to immediately receive a message.
+    ///
+    /// This method will either receive a message from the channel immediately or return an error
+    /// if the channel is empty.
+    pub fn try_recv(&self) -> Result<T, TryRecvError> {
+        self.lock(|c| c.try_recv())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use core::time::Duration;
+
+    use futures::task::SpawnExt;
+    use futures_executor::ThreadPool;
+    use futures_timer::Delay;
+
+    use crate::blocking_mutex::raw::{CriticalSectionRawMutex, NoopRawMutex};
+    use crate::util::Forever;
+
+    use super::*;
+
+    fn capacity<T, const N: usize>(c: &ChannelState<T, N>) -> usize {
+        c.queue.capacity() - c.queue.len()
+    }
+
+    #[test]
+    fn sending_once() {
+        let mut c = ChannelState::<u32, 3>::new();
+        assert!(c.try_send(1).is_ok());
+        assert_eq!(capacity(&c), 2);
+    }
+
+    #[test]
+    fn sending_when_full() {
+        let mut c = ChannelState::<u32, 3>::new();
+        let _ = c.try_send(1);
+        let _ = c.try_send(1);
+        let _ = c.try_send(1);
+        match c.try_send(2) {
+            Err(TrySendError::Full(2)) => assert!(true),
+            _ => assert!(false),
+        }
+        assert_eq!(capacity(&c), 0);
+    }
+
+    #[test]
+    fn receiving_once_with_one_send() {
+        let mut c = ChannelState::<u32, 3>::new();
+        assert!(c.try_send(1).is_ok());
+        assert_eq!(c.try_recv().unwrap(), 1);
+        assert_eq!(capacity(&c), 3);
+    }
+
+    #[test]
+    fn receiving_when_empty() {
+        let mut c = ChannelState::<u32, 3>::new();
+        match c.try_recv() {
+            Err(TryRecvError::Empty) => assert!(true),
+            _ => assert!(false),
+        }
+        assert_eq!(capacity(&c), 3);
+    }
+
+    #[test]
+    fn simple_send_and_receive() {
+        let c = Channel::<NoopRawMutex, u32, 3>::new();
+        assert!(c.try_send(1).is_ok());
+        assert_eq!(c.try_recv().unwrap(), 1);
+    }
+
+    #[futures_test::test]
+    async fn receiver_receives_given_try_send_async() {
+        let executor = ThreadPool::new().unwrap();
+
+        static CHANNEL: Forever<Channel<CriticalSectionRawMutex, u32, 3>> = Forever::new();
+        let c = &*CHANNEL.put(Channel::new());
+        let c2 = c;
+        assert!(executor
+            .spawn(async move {
+                assert!(c2.try_send(1).is_ok());
+            })
+            .is_ok());
+        assert_eq!(c.recv().await, 1);
+    }
+
+    #[futures_test::test]
+    async fn sender_send_completes_if_capacity() {
+        let c = Channel::<CriticalSectionRawMutex, u32, 1>::new();
+        c.send(1).await;
+        assert_eq!(c.recv().await, 1);
+    }
+
+    #[futures_test::test]
+    async fn senders_sends_wait_until_capacity() {
+        let executor = ThreadPool::new().unwrap();
+
+        static CHANNEL: Forever<Channel<CriticalSectionRawMutex, u32, 1>> = Forever::new();
+        let c = &*CHANNEL.put(Channel::new());
+        assert!(c.try_send(1).is_ok());
+
+        let c2 = c;
+        let send_task_1 = executor.spawn_with_handle(async move { c2.send(2).await });
+        let c2 = c;
+        let send_task_2 = executor.spawn_with_handle(async move { c2.send(3).await });
+        // Wish I could think of a means of determining that the async send is waiting instead.
+        // However, I've used the debugger to observe that the send does indeed wait.
+        Delay::new(Duration::from_millis(500)).await;
+        assert_eq!(c.recv().await, 1);
+        assert!(executor
+            .spawn(async move {
+                loop {
+                    c.recv().await;
+                }
+            })
+            .is_ok());
+        send_task_1.unwrap().await;
+        send_task_2.unwrap().await;
+    }
+}
diff --git a/embassy/src/channel/mod.rs b/embassy/src/channel/mod.rs
index 9e8c67ee9..e51a442df 100644
--- a/embassy/src/channel/mod.rs
+++ b/embassy/src/channel/mod.rs
@@ -1,4 +1,4 @@
 //! Async channels
 
-pub mod mpsc;
+pub mod channel;
 pub mod signal;
diff --git a/embassy/src/channel/mpsc.rs b/embassy/src/channel/mpsc.rs
deleted file mode 100644
index 32787d810..000000000
--- a/embassy/src/channel/mpsc.rs
+++ /dev/null
@@ -1,822 +0,0 @@
-//! A multi-producer, single-consumer queue for sending values between
-//! asynchronous tasks. This queue takes a Mutex type so that various
-//! targets can be attained. For example, a ThreadModeMutex can be used
-//! for single-core Cortex-M targets where messages are only passed
-//! between tasks running in thread mode. Similarly, a CriticalSectionMutex
-//! can also be used for single-core targets where messages are to be
-//! passed from exception mode e.g. out of an interrupt handler.
-//!
-//! This module provides a bounded channel that has a limit on the number of
-//! messages that it can store, and if this limit is reached, trying to send
-//! another message will result in an error being returned.
-//!
-//! Similar to the `mpsc` channels provided by `std`, the channel constructor
-//! functions provide separate send and receive handles, [`Sender`] and
-//! [`Receiver`]. If there is no message to read, the current task will be
-//! notified when a new value is sent. [`Sender`] allows sending values into
-//! the channel. If the bounded channel is at capacity, the send is rejected.
-//!
-//! # Disconnection
-//!
-//! When all [`Sender`] handles have been dropped, it is no longer
-//! possible to send values into the channel. This is considered the termination
-//! event of the stream.
-//!
-//! If the [`Receiver`] handle is dropped, then messages can no longer
-//! be read out of the channel. In this case, all further attempts to send will
-//! result in an error.
-//!
-//! # Clean Shutdown
-//!
-//! When the [`Receiver`] is dropped, it is possible for unprocessed messages to
-//! remain in the channel. Instead, it is usually desirable to perform a "clean"
-//! shutdown. To do this, the receiver first calls `close`, which will prevent
-//! any further messages to be sent into the channel. Then, the receiver
-//! consumes the channel to completion, at which point the receiver can be
-//! dropped.
-//!
-//! This channel and its associated types were derived from <https://docs.rs/tokio/0.1.22/tokio/sync/mpsc/fn.channel.html>
-
-use core::cell::RefCell;
-use core::fmt;
-use core::pin::Pin;
-use core::task::Context;
-use core::task::Poll;
-use core::task::Waker;
-
-use futures::Future;
-use heapless::Deque;
-
-use crate::blocking_mutex::raw::RawMutex;
-use crate::blocking_mutex::Mutex;
-use crate::waitqueue::WakerRegistration;
-
-/// Send values to the associated `Receiver`.
-///
-/// Instances are created by the [`split`](split) function.
-pub struct Sender<'ch, M, T, const N: usize>
-where
-    M: RawMutex,
-{
-    channel: &'ch Channel<M, T, N>,
-}
-
-/// Receive values from the associated `Sender`.
-///
-/// Instances are created by the [`split`](split) function.
-pub struct Receiver<'ch, M, T, const N: usize>
-where
-    M: RawMutex,
-{
-    channel: &'ch Channel<M, T, N>,
-}
-
-/// Splits a bounded mpsc channel into a `Sender` and `Receiver`.
-///
-/// All data sent on `Sender` will become available on `Receiver` in the same
-/// order as it was sent.
-///
-/// The `Sender` can be cloned to `send` to the same channel from multiple code
-/// locations. Only one `Receiver` is valid.
-///
-/// If the `Receiver` is disconnected while trying to `send`, the `send` method
-/// will return a `SendError`. Similarly, if `Sender` is disconnected while
-/// trying to `recv`, the `recv` method will return a `RecvError`.
-///
-/// Note that when splitting the channel, the sender and receiver cannot outlive
-/// their channel. The following will therefore fail compilation:
-////
-/// ```compile_fail
-/// use embassy::channel::mpsc;
-/// use embassy::channel::mpsc::{Channel, WithThreadModeOnly};
-///
-/// let (sender, receiver) = {
-///    let mut channel = Channel::<WithThreadModeOnly, u32, 3>::with_thread_mode_only();
-///     mpsc::split(&mut channel)
-/// };
-/// ```
-pub fn split<M, T, const N: usize>(
-    channel: &mut Channel<M, T, N>,
-) -> (Sender<M, T, N>, Receiver<M, T, N>)
-where
-    M: RawMutex,
-{
-    let sender = Sender { channel };
-    let receiver = Receiver { channel };
-    channel.lock(|c| {
-        c.register_receiver();
-        c.register_sender();
-    });
-    (sender, receiver)
-}
-
-impl<'ch, M, T, const N: usize> Receiver<'ch, M, T, N>
-where
-    M: RawMutex,
-{
-    /// Receives the next value for this receiver.
-    ///
-    /// This method returns `None` if the channel has been closed and there are
-    /// no remaining messages in the channel's buffer. This indicates that no
-    /// further values can ever be received from this `Receiver`. The channel is
-    /// closed when all senders have been dropped, or when [`close`] is called.
-    ///
-    /// If there are no messages in the channel's buffer, but the channel has
-    /// not yet been closed, this method will sleep until a message is sent or
-    /// the channel is closed.
-    ///
-    /// Note that if [`close`] is called, but there are still outstanding
-    /// messages from before it was closed, the channel is not considered
-    /// closed by `recv` until they are all consumed.
-    ///
-    /// [`close`]: Self::close
-    pub fn recv(&mut self) -> RecvFuture<'_, M, T, N> {
-        RecvFuture {
-            channel: self.channel,
-        }
-    }
-
-    /// Attempts to immediately receive a message on this `Receiver`
-    ///
-    /// This method will either receive a message from the channel immediately or return an error
-    /// if the channel is empty.
-    pub fn try_recv(&self) -> Result<T, TryRecvError> {
-        self.channel.lock(|c| c.try_recv())
-    }
-
-    /// Closes the receiving half of a channel without dropping it.
-    ///
-    /// This prevents any further messages from being sent on the channel while
-    /// still enabling the receiver to drain messages that are buffered.
-    ///
-    /// To guarantee that no messages are dropped, after calling `close()`,
-    /// `recv()` must be called until `None` is returned. If there are
-    /// outstanding messages, the `recv` method will not return `None`
-    /// until those are released.
-    ///
-    pub fn close(&mut self) {
-        self.channel.lock(|c| c.close())
-    }
-}
-
-impl<'ch, M, T, const N: usize> Drop for Receiver<'ch, M, T, N>
-where
-    M: RawMutex,
-{
-    fn drop(&mut self) {
-        self.channel.lock(|c| c.deregister_receiver())
-    }
-}
-
-pub struct RecvFuture<'ch, M, T, const N: usize>
-where
-    M: RawMutex,
-{
-    channel: &'ch Channel<M, T, N>,
-}
-
-impl<'ch, M, T, const N: usize> Future for RecvFuture<'ch, M, T, N>
-where
-    M: RawMutex,
-{
-    type Output = Option<T>;
-
-    fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<T>> {
-        self.channel
-            .lock(|c| match c.try_recv_with_context(Some(cx)) {
-                Ok(v) => Poll::Ready(Some(v)),
-                Err(TryRecvError::Closed) => Poll::Ready(None),
-                Err(TryRecvError::Empty) => Poll::Pending,
-            })
-    }
-}
-
-impl<'ch, M, T, const N: usize> Sender<'ch, M, T, N>
-where
-    M: RawMutex,
-{
-    /// Sends a value, waiting until there is capacity.
-    ///
-    /// A successful send occurs when it is determined that the other end of the
-    /// channel has not hung up already. An unsuccessful send would be one where
-    /// the corresponding receiver has already been closed. Note that a return
-    /// value of `Err` means that the data will never be received, but a return
-    /// value of `Ok` does not mean that the data will be received. It is
-    /// possible for the corresponding receiver to hang up immediately after
-    /// this function returns `Ok`.
-    ///
-    /// # Errors
-    ///
-    /// If the receive half of the channel is closed, either due to [`close`]
-    /// being called or the [`Receiver`] handle dropping, the function returns
-    /// an error. The error includes the value passed to `send`.
-    ///
-    /// [`close`]: Receiver::close
-    /// [`Receiver`]: Receiver
-    pub fn send(&self, message: T) -> SendFuture<'ch, M, T, N> {
-        SendFuture {
-            channel: self.channel,
-            message: Some(message),
-        }
-    }
-
-    /// Attempts to immediately send a message on this `Sender`
-    ///
-    /// This method differs from [`send`] by returning immediately if the channel's
-    /// buffer is full or no receiver is waiting to acquire some data. Compared
-    /// with [`send`], this function has two failure cases instead of one (one for
-    /// disconnection, one for a full buffer).
-    ///
-    /// # Errors
-    ///
-    /// If the channel capacity has been reached, i.e., the channel has `n`
-    /// buffered values where `n` is the argument passed to [`channel`], then an
-    /// error is returned.
-    ///
-    /// If the receive half of the channel is closed, either due to [`close`]
-    /// being called or the [`Receiver`] handle dropping, the function returns
-    /// an error. The error includes the value passed to `send`.
-    ///
-    /// [`send`]: Sender::send
-    /// [`channel`]: channel
-    /// [`close`]: Receiver::close
-    pub fn try_send(&self, message: T) -> Result<(), TrySendError<T>> {
-        self.channel.lock(|c| c.try_send(message))
-    }
-
-    /// Completes when the receiver has dropped.
-    ///
-    /// This allows the producers to get notified when interest in the produced
-    /// values is canceled and immediately stop doing work.
-    pub async fn closed(&self) {
-        CloseFuture {
-            channel: self.channel,
-        }
-        .await
-    }
-
-    /// Checks if the channel has been closed. This happens when the
-    /// [`Receiver`] is dropped, or when the [`Receiver::close`] method is
-    /// called.
-    ///
-    /// [`Receiver`]: Receiver
-    /// [`Receiver::close`]: Receiver::close
-    pub fn is_closed(&self) -> bool {
-        self.channel.lock(|c| c.is_closed())
-    }
-}
-
-pub struct SendFuture<'ch, M, T, const N: usize>
-where
-    M: RawMutex,
-{
-    channel: &'ch Channel<M, T, N>,
-    message: Option<T>,
-}
-
-impl<'ch, M, T, const N: usize> Future for SendFuture<'ch, M, T, N>
-where
-    M: RawMutex,
-{
-    type Output = Result<(), SendError<T>>;
-
-    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
-        match self.message.take() {
-            Some(m) => match self.channel.lock(|c| c.try_send_with_context(m, Some(cx))) {
-                Ok(..) => Poll::Ready(Ok(())),
-                Err(TrySendError::Closed(m)) => Poll::Ready(Err(SendError(m))),
-                Err(TrySendError::Full(m)) => {
-                    self.message = Some(m);
-                    Poll::Pending
-                }
-            },
-            None => panic!("Message cannot be None"),
-        }
-    }
-}
-
-impl<'ch, M, T, const N: usize> Unpin for SendFuture<'ch, M, T, N> where M: RawMutex {}
-
-struct CloseFuture<'ch, M, T, const N: usize>
-where
-    M: RawMutex,
-{
-    channel: &'ch Channel<M, T, N>,
-}
-
-impl<'ch, M, T, const N: usize> Future for CloseFuture<'ch, M, T, N>
-where
-    M: RawMutex,
-{
-    type Output = ();
-
-    fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
-        if self.channel.lock(|c| c.is_closed_with_context(Some(cx))) {
-            Poll::Ready(())
-        } else {
-            Poll::Pending
-        }
-    }
-}
-
-impl<'ch, M, T, const N: usize> Drop for Sender<'ch, M, T, N>
-where
-    M: RawMutex,
-{
-    fn drop(&mut self) {
-        self.channel.lock(|c| c.deregister_sender())
-    }
-}
-
-impl<'ch, M, T, const N: usize> Clone for Sender<'ch, M, T, N>
-where
-    M: RawMutex,
-{
-    fn clone(&self) -> Self {
-        self.channel.lock(|c| c.register_sender());
-        Sender {
-            channel: self.channel,
-        }
-    }
-}
-
-/// An error returned from the [`try_recv`] method.
-///
-/// [`try_recv`]: Receiver::try_recv
-#[derive(PartialEq, Eq, Clone, Copy, Debug)]
-#[cfg_attr(feature = "defmt", derive(defmt::Format))]
-pub enum TryRecvError {
-    /// A message could not be received because the channel is empty.
-    Empty,
-
-    /// The message could not be received because the channel is empty and closed.
-    Closed,
-}
-
-/// Error returned by the `Sender`.
-#[derive(Debug)]
-pub struct SendError<T>(pub T);
-
-impl<T> fmt::Display for SendError<T> {
-    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(fmt, "channel closed")
-    }
-}
-
-#[cfg(feature = "defmt")]
-impl<T> defmt::Format for SendError<T> {
-    fn format(&self, fmt: defmt::Formatter<'_>) {
-        defmt::write!(fmt, "channel closed")
-    }
-}
-
-/// This enumeration is the list of the possible error outcomes for the
-/// [try_send](Sender::try_send) method.
-#[derive(Debug)]
-pub enum TrySendError<T> {
-    /// The data could not be sent on the channel because the channel is
-    /// currently full and sending would require blocking.
-    Full(T),
-
-    /// The receive half of the channel was explicitly closed or has been
-    /// dropped.
-    Closed(T),
-}
-
-impl<T> fmt::Display for TrySendError<T> {
-    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(
-            fmt,
-            "{}",
-            match self {
-                TrySendError::Full(..) => "no available capacity",
-                TrySendError::Closed(..) => "channel closed",
-            }
-        )
-    }
-}
-
-#[cfg(feature = "defmt")]
-impl<T> defmt::Format for TrySendError<T> {
-    fn format(&self, fmt: defmt::Formatter<'_>) {
-        match self {
-            TrySendError::Full(..) => defmt::write!(fmt, "no available capacity"),
-            TrySendError::Closed(..) => defmt::write!(fmt, "channel closed"),
-        }
-    }
-}
-
-struct ChannelState<T, const N: usize> {
-    queue: Deque<T, N>,
-    closed: bool,
-    receiver_registered: bool,
-    senders_registered: u32,
-    receiver_waker: WakerRegistration,
-    senders_waker: WakerRegistration,
-}
-
-impl<T, const N: usize> ChannelState<T, N> {
-    const fn new() -> Self {
-        ChannelState {
-            queue: Deque::new(),
-            closed: false,
-            receiver_registered: false,
-            senders_registered: 0,
-            receiver_waker: WakerRegistration::new(),
-            senders_waker: WakerRegistration::new(),
-        }
-    }
-
-    fn try_recv(&mut self) -> Result<T, TryRecvError> {
-        self.try_recv_with_context(None)
-    }
-
-    fn try_recv_with_context(&mut self, cx: Option<&mut Context<'_>>) -> Result<T, TryRecvError> {
-        if self.queue.is_full() {
-            self.senders_waker.wake();
-        }
-
-        if let Some(message) = self.queue.pop_front() {
-            Ok(message)
-        } else if !self.closed {
-            if let Some(cx) = cx {
-                self.set_receiver_waker(cx.waker());
-            }
-            Err(TryRecvError::Empty)
-        } else {
-            Err(TryRecvError::Closed)
-        }
-    }
-
-    fn try_send(&mut self, message: T) -> Result<(), TrySendError<T>> {
-        self.try_send_with_context(message, None)
-    }
-
-    fn try_send_with_context(
-        &mut self,
-        message: T,
-        cx: Option<&mut Context<'_>>,
-    ) -> Result<(), TrySendError<T>> {
-        if self.closed {
-            return Err(TrySendError::Closed(message));
-        }
-
-        match self.queue.push_back(message) {
-            Ok(()) => {
-                self.receiver_waker.wake();
-
-                Ok(())
-            }
-            Err(message) => {
-                cx.into_iter()
-                    .for_each(|cx| self.set_senders_waker(cx.waker()));
-                Err(TrySendError::Full(message))
-            }
-        }
-    }
-
-    fn close(&mut self) {
-        self.receiver_waker.wake();
-        self.closed = true;
-    }
-
-    fn is_closed(&mut self) -> bool {
-        self.is_closed_with_context(None)
-    }
-
-    fn is_closed_with_context(&mut self, cx: Option<&mut Context<'_>>) -> bool {
-        if self.closed {
-            cx.into_iter()
-                .for_each(|cx| self.set_senders_waker(cx.waker()));
-            true
-        } else {
-            false
-        }
-    }
-
-    fn register_receiver(&mut self) {
-        assert!(!self.receiver_registered);
-        self.receiver_registered = true;
-    }
-
-    fn deregister_receiver(&mut self) {
-        if self.receiver_registered {
-            self.closed = true;
-            self.senders_waker.wake();
-        }
-        self.receiver_registered = false;
-    }
-
-    fn register_sender(&mut self) {
-        self.senders_registered += 1;
-    }
-
-    fn deregister_sender(&mut self) {
-        assert!(self.senders_registered > 0);
-        self.senders_registered -= 1;
-        if self.senders_registered == 0 {
-            self.receiver_waker.wake();
-            self.closed = true;
-        }
-    }
-
-    fn set_receiver_waker(&mut self, receiver_waker: &Waker) {
-        self.receiver_waker.register(receiver_waker);
-    }
-
-    fn set_senders_waker(&mut self, senders_waker: &Waker) {
-        // Dispose of any existing sender causing them to be polled again.
-        // This could cause a spin given multiple concurrent senders, however given that
-        // most sends only block waiting for the receiver to become active, this should
-        // be a short-lived activity. The upside is a greatly simplified implementation
-        // that avoids the need for intrusive linked-lists and unsafe operations on pinned
-        // pointers.
-        self.senders_waker.wake();
-        self.senders_waker.register(senders_waker);
-    }
-}
-
-/// A a bounded mpsc channel for communicating between asynchronous tasks
-/// with backpressure.
-///
-/// The channel will buffer up to the provided number of messages.  Once the
-/// buffer is full, attempts to `send` new messages will wait until a message is
-/// received from the channel.
-///
-/// All data sent will become available in the same order as it was sent.
-pub struct Channel<M, T, const N: usize>
-where
-    M: RawMutex,
-{
-    inner: Mutex<M, RefCell<ChannelState<T, N>>>,
-}
-
-impl<M, T, const N: usize> Channel<M, T, N>
-where
-    M: RawMutex,
-{
-    /// Establish a new bounded channel. For example, to create one with a NoopMutex:
-    ///
-    /// ```
-    /// use embassy::channel::mpsc;
-    /// use embassy::blocking_mutex::raw::NoopRawMutex;
-    /// use embassy::channel::mpsc::Channel;
-    ///
-    /// // Declare a bounded channel of 3 u32s.
-    /// let mut channel = Channel::<NoopRawMutex, u32, 3>::new();
-    /// // once we have a channel, obtain its sender and receiver
-    /// let (sender, receiver) = mpsc::split(&mut channel);
-    /// ```
-    #[cfg(feature = "nightly")]
-    pub const fn new() -> Self {
-        Self {
-            inner: Mutex::new(RefCell::new(ChannelState::new())),
-        }
-    }
-
-    /// Establish a new bounded channel. For example, to create one with a NoopMutex:
-    ///
-    /// ```
-    /// use embassy::channel::mpsc;
-    /// use embassy::blocking_mutex::raw::NoopRawMutex;
-    /// use embassy::channel::mpsc::Channel;
-    ///
-    /// // Declare a bounded channel of 3 u32s.
-    /// let mut channel = Channel::<NoopRawMutex, u32, 3>::new();
-    /// // once we have a channel, obtain its sender and receiver
-    /// let (sender, receiver) = mpsc::split(&mut channel);
-    /// ```
-    #[cfg(not(feature = "nightly"))]
-    pub fn new() -> Self {
-        Self {
-            inner: Mutex::new(RefCell::new(ChannelState::new())),
-        }
-    }
-
-    fn lock<R>(&self, f: impl FnOnce(&mut ChannelState<T, N>) -> R) -> R {
-        self.inner.lock(|rc| f(&mut *rc.borrow_mut()))
-    }
-}
-
-#[cfg(test)]
-mod tests {
-    use core::time::Duration;
-
-    use futures::task::SpawnExt;
-    use futures_executor::ThreadPool;
-    use futures_timer::Delay;
-
-    use crate::blocking_mutex::raw::{CriticalSectionRawMutex, NoopRawMutex};
-    use crate::util::Forever;
-
-    use super::*;
-
-    fn capacity<T, const N: usize>(c: &ChannelState<T, N>) -> usize {
-        c.queue.capacity() - c.queue.len()
-    }
-
-    #[test]
-    fn sending_once() {
-        let mut c = ChannelState::<u32, 3>::new();
-        assert!(c.try_send(1).is_ok());
-        assert_eq!(capacity(&c), 2);
-    }
-
-    #[test]
-    fn sending_when_full() {
-        let mut c = ChannelState::<u32, 3>::new();
-        let _ = c.try_send(1);
-        let _ = c.try_send(1);
-        let _ = c.try_send(1);
-        match c.try_send(2) {
-            Err(TrySendError::Full(2)) => assert!(true),
-            _ => assert!(false),
-        }
-        assert_eq!(capacity(&c), 0);
-    }
-
-    #[test]
-    fn sending_when_closed() {
-        let mut c = ChannelState::<u32, 3>::new();
-        c.closed = true;
-        match c.try_send(2) {
-            Err(TrySendError::Closed(2)) => assert!(true),
-            _ => assert!(false),
-        }
-    }
-
-    #[test]
-    fn receiving_once_with_one_send() {
-        let mut c = ChannelState::<u32, 3>::new();
-        assert!(c.try_send(1).is_ok());
-        assert_eq!(c.try_recv().unwrap(), 1);
-        assert_eq!(capacity(&c), 3);
-    }
-
-    #[test]
-    fn receiving_when_empty() {
-        let mut c = ChannelState::<u32, 3>::new();
-        match c.try_recv() {
-            Err(TryRecvError::Empty) => assert!(true),
-            _ => assert!(false),
-        }
-        assert_eq!(capacity(&c), 3);
-    }
-
-    #[test]
-    fn receiving_when_closed() {
-        let mut c = ChannelState::<u32, 3>::new();
-        c.closed = true;
-        match c.try_recv() {
-            Err(TryRecvError::Closed) => assert!(true),
-            _ => assert!(false),
-        }
-    }
-
-    #[test]
-    fn simple_send_and_receive() {
-        let mut c = Channel::<NoopRawMutex, u32, 3>::new();
-        let (s, r) = split(&mut c);
-        assert!(s.clone().try_send(1).is_ok());
-        assert_eq!(r.try_recv().unwrap(), 1);
-    }
-
-    #[test]
-    fn should_close_without_sender() {
-        let mut c = Channel::<NoopRawMutex, u32, 3>::new();
-        let (s, r) = split(&mut c);
-        drop(s);
-        match r.try_recv() {
-            Err(TryRecvError::Closed) => assert!(true),
-            _ => assert!(false),
-        }
-    }
-
-    #[test]
-    fn should_close_once_drained() {
-        let mut c = Channel::<NoopRawMutex, u32, 3>::new();
-        let (s, r) = split(&mut c);
-        assert!(s.try_send(1).is_ok());
-        drop(s);
-        assert_eq!(r.try_recv().unwrap(), 1);
-        match r.try_recv() {
-            Err(TryRecvError::Closed) => assert!(true),
-            _ => assert!(false),
-        }
-    }
-
-    #[test]
-    fn should_reject_send_when_receiver_dropped() {
-        let mut c = Channel::<NoopRawMutex, u32, 3>::new();
-        let (s, r) = split(&mut c);
-        drop(r);
-        match s.try_send(1) {
-            Err(TrySendError::Closed(1)) => assert!(true),
-            _ => assert!(false),
-        }
-    }
-
-    #[test]
-    fn should_reject_send_when_channel_closed() {
-        let mut c = Channel::<NoopRawMutex, u32, 3>::new();
-        let (s, mut r) = split(&mut c);
-        assert!(s.try_send(1).is_ok());
-        r.close();
-        assert_eq!(r.try_recv().unwrap(), 1);
-        match r.try_recv() {
-            Err(TryRecvError::Closed) => assert!(true),
-            _ => assert!(false),
-        }
-        assert!(s.is_closed());
-    }
-
-    #[futures_test::test]
-    async fn receiver_closes_when_sender_dropped_async() {
-        let executor = ThreadPool::new().unwrap();
-
-        static CHANNEL: Forever<Channel<CriticalSectionRawMutex, u32, 3>> = Forever::new();
-        let c = CHANNEL.put(Channel::new());
-        let (s, mut r) = split(c);
-        assert!(executor
-            .spawn(async move {
-                drop(s);
-            })
-            .is_ok());
-        assert_eq!(r.recv().await, None);
-    }
-
-    #[futures_test::test]
-    async fn receiver_receives_given_try_send_async() {
-        let executor = ThreadPool::new().unwrap();
-
-        static CHANNEL: Forever<Channel<CriticalSectionRawMutex, u32, 3>> = Forever::new();
-        let c = CHANNEL.put(Channel::new());
-        let (s, mut r) = split(c);
-        assert!(executor
-            .spawn(async move {
-                assert!(s.try_send(1).is_ok());
-            })
-            .is_ok());
-        assert_eq!(r.recv().await, Some(1));
-    }
-
-    #[futures_test::test]
-    async fn sender_send_completes_if_capacity() {
-        let mut c = Channel::<CriticalSectionRawMutex, u32, 1>::new();
-        let (s, mut r) = split(&mut c);
-        assert!(s.send(1).await.is_ok());
-        assert_eq!(r.recv().await, Some(1));
-    }
-
-    #[futures_test::test]
-    async fn sender_send_completes_if_closed() {
-        static CHANNEL: Forever<Channel<CriticalSectionRawMutex, u32, 1>> = Forever::new();
-        let c = CHANNEL.put(Channel::new());
-        let (s, r) = split(c);
-        drop(r);
-        match s.send(1).await {
-            Err(SendError(1)) => assert!(true),
-            _ => assert!(false),
-        }
-    }
-
-    #[futures_test::test]
-    async fn senders_sends_wait_until_capacity() {
-        let executor = ThreadPool::new().unwrap();
-
-        static CHANNEL: Forever<Channel<CriticalSectionRawMutex, u32, 1>> = Forever::new();
-        let c = CHANNEL.put(Channel::new());
-        let (s0, mut r) = split(c);
-        assert!(s0.try_send(1).is_ok());
-        let s1 = s0.clone();
-        let send_task_1 = executor.spawn_with_handle(async move { s0.send(2).await });
-        let send_task_2 = executor.spawn_with_handle(async move { s1.send(3).await });
-        // Wish I could think of a means of determining that the async send is waiting instead.
-        // However, I've used the debugger to observe that the send does indeed wait.
-        Delay::new(Duration::from_millis(500)).await;
-        assert_eq!(r.recv().await, Some(1));
-        assert!(executor
-            .spawn(async move { while let Some(_) = r.recv().await {} })
-            .is_ok());
-        assert!(send_task_1.unwrap().await.is_ok());
-        assert!(send_task_2.unwrap().await.is_ok());
-    }
-
-    #[futures_test::test]
-    async fn sender_close_completes_if_closing() {
-        static CHANNEL: Forever<Channel<CriticalSectionRawMutex, u32, 1>> = Forever::new();
-        let c = CHANNEL.put(Channel::new());
-        let (s, mut r) = split(c);
-        r.close();
-        s.closed().await;
-    }
-
-    #[futures_test::test]
-    async fn sender_close_completes_if_closed() {
-        static CHANNEL: Forever<Channel<CriticalSectionRawMutex, u32, 1>> = Forever::new();
-        let c = CHANNEL.put(Channel::new());
-        let (s, r) = split(c);
-        drop(r);
-        s.closed().await;
-    }
-}
diff --git a/embassy/src/channel/signal.rs b/embassy/src/channel/signal.rs
index 027f4f47c..e1f6c4b1d 100644
--- a/embassy/src/channel/signal.rs
+++ b/embassy/src/channel/signal.rs
@@ -5,7 +5,7 @@ use core::task::{Context, Poll, Waker};
 
 /// Synchronization primitive. Allows creating awaitable signals that may be passed between tasks.
 /// For a simple use-case where the receiver is only ever interested in the latest value of
-/// something, Signals work well. For more advanced use cases, please consider [crate::channel::mpsc].
+/// something, Signals work well. For more advanced use cases, you might want to use [`Channel`](crate::channel::channel::Channel) instead..
 ///
 /// Signals are generally declared as being a static const and then borrowed as required.
 ///
diff --git a/examples/nrf/src/bin/channel.rs b/examples/nrf/src/bin/channel.rs
new file mode 100644
index 000000000..476ec09a1
--- /dev/null
+++ b/examples/nrf/src/bin/channel.rs
@@ -0,0 +1,45 @@
+#![no_std]
+#![no_main]
+#![feature(type_alias_impl_trait)]
+
+use defmt::unwrap;
+use embassy::blocking_mutex::raw::ThreadModeRawMutex;
+use embassy::channel::channel::Channel;
+use embassy::executor::Spawner;
+use embassy::time::{Duration, Timer};
+use embassy_nrf::gpio::{Level, Output, OutputDrive};
+use embassy_nrf::Peripherals;
+
+use defmt_rtt as _; // global logger
+use panic_probe as _;
+
+enum LedState {
+    On,
+    Off,
+}
+
+static CHANNEL: Channel<ThreadModeRawMutex, LedState, 1> = Channel::new();
+
+#[embassy::task]
+async fn my_task() {
+    loop {
+        CHANNEL.send(LedState::On).await;
+        Timer::after(Duration::from_secs(1)).await;
+        CHANNEL.send(LedState::Off).await;
+        Timer::after(Duration::from_secs(1)).await;
+    }
+}
+
+#[embassy::main]
+async fn main(spawner: Spawner, p: Peripherals) {
+    let mut led = Output::new(p.P0_13, Level::Low, OutputDrive::Standard);
+
+    unwrap!(spawner.spawn(my_task()));
+
+    loop {
+        match CHANNEL.recv().await {
+            LedState::On => led.set_high(),
+            LedState::Off => led.set_low(),
+        }
+    }
+}
diff --git a/examples/nrf/src/bin/channel_sender_receiver.rs b/examples/nrf/src/bin/channel_sender_receiver.rs
new file mode 100644
index 000000000..c79f2fd6b
--- /dev/null
+++ b/examples/nrf/src/bin/channel_sender_receiver.rs
@@ -0,0 +1,52 @@
+#![no_std]
+#![no_main]
+#![feature(type_alias_impl_trait)]
+
+use defmt::unwrap;
+use embassy::blocking_mutex::raw::NoopRawMutex;
+use embassy::channel::channel::{Channel, Receiver, Sender};
+use embassy::executor::Spawner;
+use embassy::time::{Duration, Timer};
+use embassy::util::Forever;
+use embassy_nrf::gpio::{AnyPin, Level, Output, OutputDrive, Pin};
+use embassy_nrf::Peripherals;
+
+use defmt_rtt as _; // global logger
+use panic_probe as _;
+
+enum LedState {
+    On,
+    Off,
+}
+
+static CHANNEL: Forever<Channel<NoopRawMutex, LedState, 1>> = Forever::new();
+
+#[embassy::task]
+async fn send_task(sender: Sender<'static, NoopRawMutex, LedState, 1>) {
+    loop {
+        sender.send(LedState::On).await;
+        Timer::after(Duration::from_secs(1)).await;
+        sender.send(LedState::Off).await;
+        Timer::after(Duration::from_secs(1)).await;
+    }
+}
+
+#[embassy::task]
+async fn recv_task(led: AnyPin, receiver: Receiver<'static, NoopRawMutex, LedState, 1>) {
+    let mut led = Output::new(led, Level::Low, OutputDrive::Standard);
+
+    loop {
+        match receiver.recv().await {
+            LedState::On => led.set_high(),
+            LedState::Off => led.set_low(),
+        }
+    }
+}
+
+#[embassy::main]
+async fn main(spawner: Spawner, p: Peripherals) {
+    let channel = CHANNEL.put(Channel::new());
+
+    unwrap!(spawner.spawn(send_task(channel.sender())));
+    unwrap!(spawner.spawn(recv_task(p.P0_13.degrade(), channel.receiver())));
+}
diff --git a/examples/nrf/src/bin/mpsc.rs b/examples/nrf/src/bin/mpsc.rs
deleted file mode 100644
index 0cb182755..000000000
--- a/examples/nrf/src/bin/mpsc.rs
+++ /dev/null
@@ -1,60 +0,0 @@
-#![no_std]
-#![no_main]
-#![feature(type_alias_impl_trait)]
-
-use defmt::unwrap;
-use embassy::blocking_mutex::raw::NoopRawMutex;
-use embassy::channel::mpsc::{self, Channel, Sender, TryRecvError};
-use embassy::executor::Spawner;
-use embassy::time::{Duration, Timer};
-use embassy::util::Forever;
-use embassy_nrf::gpio::{Level, Output, OutputDrive};
-use embassy_nrf::Peripherals;
-
-use defmt_rtt as _; // global logger
-use panic_probe as _;
-
-enum LedState {
-    On,
-    Off,
-}
-
-static CHANNEL: Forever<Channel<NoopRawMutex, LedState, 1>> = Forever::new();
-
-#[embassy::task(pool_size = 1)]
-async fn my_task(sender: Sender<'static, NoopRawMutex, LedState, 1>) {
-    loop {
-        let _ = sender.send(LedState::On).await;
-        Timer::after(Duration::from_secs(1)).await;
-        let _ = sender.send(LedState::Off).await;
-        Timer::after(Duration::from_secs(1)).await;
-    }
-}
-
-#[embassy::main]
-async fn main(spawner: Spawner, p: Peripherals) {
-    let mut led = Output::new(p.P0_13, Level::Low, OutputDrive::Standard);
-
-    let channel = CHANNEL.put(Channel::new());
-    let (sender, mut receiver) = mpsc::split(channel);
-
-    unwrap!(spawner.spawn(my_task(sender)));
-
-    // We could just loop on `receiver.recv()` for simplicity. The code below
-    // is optimized to drain the queue as fast as possible in the spirit of
-    // handling events as fast as possible. This optimization is benign when in
-    // thread mode, but can be useful when interrupts are sending messages
-    // with the channel having been created via with_critical_sections.
-    loop {
-        let maybe_message = match receiver.try_recv() {
-            m @ Ok(..) => m.ok(),
-            Err(TryRecvError::Empty) => receiver.recv().await,
-            Err(TryRecvError::Closed) => break,
-        };
-        match maybe_message {
-            Some(LedState::On) => led.set_high(),
-            Some(LedState::Off) => led.set_low(),
-            _ => (),
-        }
-    }
-}
diff --git a/examples/nrf/src/bin/uart_split.rs b/examples/nrf/src/bin/uart_split.rs
index 909429b1a..3fde2f0d8 100644
--- a/examples/nrf/src/bin/uart_split.rs
+++ b/examples/nrf/src/bin/uart_split.rs
@@ -3,10 +3,9 @@
 #![feature(type_alias_impl_trait)]
 
 use defmt::*;
-use embassy::blocking_mutex::raw::NoopRawMutex;
-use embassy::channel::mpsc::{self, Channel, Sender};
+use embassy::blocking_mutex::raw::ThreadModeRawMutex;
+use embassy::channel::channel::Channel;
 use embassy::executor::Spawner;
-use embassy::util::Forever;
 use embassy_nrf::peripherals::UARTE0;
 use embassy_nrf::uarte::UarteRx;
 use embassy_nrf::{interrupt, uarte, Peripherals};
@@ -14,7 +13,7 @@ use embassy_nrf::{interrupt, uarte, Peripherals};
 use defmt_rtt as _; // global logger
 use panic_probe as _;
 
-static CHANNEL: Forever<Channel<NoopRawMutex, [u8; 8], 1>> = Forever::new();
+static CHANNEL: Channel<ThreadModeRawMutex, [u8; 8], 1> = Channel::new();
 
 #[embassy::main]
 async fn main(spawner: Spawner, p: Peripherals) {
@@ -26,14 +25,11 @@ async fn main(spawner: Spawner, p: Peripherals) {
     let uart = uarte::Uarte::new(p.UARTE0, irq, p.P0_08, p.P0_06, config);
     let (mut tx, rx) = uart.split();
 
-    let c = CHANNEL.put(Channel::new());
-    let (s, mut r) = mpsc::split(c);
-
     info!("uarte initialized!");
 
     // Spawn a task responsible purely for reading
 
-    unwrap!(spawner.spawn(reader(rx, s)));
+    unwrap!(spawner.spawn(reader(rx)));
 
     // Message must be in SRAM
     {
@@ -48,19 +44,18 @@ async fn main(spawner: Spawner, p: Peripherals) {
     // back out the buffer we receive from the read
     // task.
     loop {
-        if let Some(buf) = r.recv().await {
-            info!("writing...");
-            unwrap!(tx.write(&buf).await);
-        }
+        let buf = CHANNEL.recv().await;
+        info!("writing...");
+        unwrap!(tx.write(&buf).await);
     }
 }
 
 #[embassy::task]
-async fn reader(mut rx: UarteRx<'static, UARTE0>, s: Sender<'static, NoopRawMutex, [u8; 8], 1>) {
+async fn reader(mut rx: UarteRx<'static, UARTE0>) {
     let mut buf = [0; 8];
     loop {
         info!("reading...");
         unwrap!(rx.read(&mut buf).await);
-        unwrap!(s.send(buf).await);
+        CHANNEL.send(buf).await;
     }
 }
diff --git a/examples/stm32f3/src/bin/button_events.rs b/examples/stm32f3/src/bin/button_events.rs
index 99aab3027..06e8eec1f 100644
--- a/examples/stm32f3/src/bin/button_events.rs
+++ b/examples/stm32f3/src/bin/button_events.rs
@@ -11,11 +11,10 @@
 #![feature(type_alias_impl_trait)]
 
 use defmt::*;
-use embassy::blocking_mutex::raw::NoopRawMutex;
-use embassy::channel::mpsc::{self, Channel, Receiver, Sender};
+use embassy::blocking_mutex::raw::ThreadModeRawMutex;
+use embassy::channel::channel::Channel;
 use embassy::executor::Spawner;
 use embassy::time::{with_timeout, Duration, Timer};
-use embassy::util::Forever;
 use embassy_stm32::exti::ExtiInput;
 use embassy_stm32::gpio::{AnyPin, Input, Level, Output, Pin, Pull, Speed};
 use embassy_stm32::peripherals::PA0;
@@ -51,14 +50,15 @@ impl<'a> Leds<'a> {
         }
     }
 
-    async fn show(&mut self, queue: &mut Receiver<'static, NoopRawMutex, ButtonEvent, 4>) {
+    async fn show(&mut self) {
         self.leds[self.current_led].set_high();
-        if let Ok(new_message) = with_timeout(Duration::from_millis(500), queue.recv()).await {
+        if let Ok(new_message) = with_timeout(Duration::from_millis(500), CHANNEL.recv()).await {
             self.leds[self.current_led].set_low();
             self.process_event(new_message).await;
         } else {
             self.leds[self.current_led].set_low();
-            if let Ok(new_message) = with_timeout(Duration::from_millis(200), queue.recv()).await {
+            if let Ok(new_message) = with_timeout(Duration::from_millis(200), CHANNEL.recv()).await
+            {
                 self.process_event(new_message).await;
             }
         }
@@ -77,15 +77,18 @@ impl<'a> Leds<'a> {
         }
     }
 
-    async fn process_event(&mut self, event: Option<ButtonEvent>) {
+    async fn process_event(&mut self, event: ButtonEvent) {
         match event {
-            Some(ButtonEvent::SingleClick) => self.move_next(),
-            Some(ButtonEvent::DoubleClick) => {
+            ButtonEvent::SingleClick => {
+                self.move_next();
+            }
+            ButtonEvent::DoubleClick => {
                 self.change_direction();
-                self.move_next()
+                self.move_next();
+            }
+            ButtonEvent::Hold => {
+                self.flash().await;
             }
-            Some(ButtonEvent::Hold) => self.flash().await,
-            _ => {}
         }
     }
 }
@@ -97,7 +100,7 @@ enum ButtonEvent {
     Hold,
 }
 
-static BUTTON_EVENTS_QUEUE: Forever<Channel<NoopRawMutex, ButtonEvent, 4>> = Forever::new();
+static CHANNEL: Channel<ThreadModeRawMutex, ButtonEvent, 4> = Channel::new();
 
 #[embassy::main]
 async fn main(spawner: Spawner, p: Peripherals) {
@@ -116,27 +119,19 @@ async fn main(spawner: Spawner, p: Peripherals) {
     ];
     let leds = Leds::new(leds);
 
-    let buttons_queue = BUTTON_EVENTS_QUEUE.put(Channel::new());
-    let (sender, receiver) = mpsc::split(buttons_queue);
-    spawner.spawn(button_waiter(button, sender)).unwrap();
-    spawner.spawn(led_blinker(leds, receiver)).unwrap();
+    spawner.spawn(button_waiter(button)).unwrap();
+    spawner.spawn(led_blinker(leds)).unwrap();
 }
 
 #[embassy::task]
-async fn led_blinker(
-    mut leds: Leds<'static>,
-    mut queue: Receiver<'static, NoopRawMutex, ButtonEvent, 4>,
-) {
+async fn led_blinker(mut leds: Leds<'static>) {
     loop {
-        leds.show(&mut queue).await;
+        leds.show().await;
     }
 }
 
 #[embassy::task]
-async fn button_waiter(
-    mut button: ExtiInput<'static, PA0>,
-    queue: Sender<'static, NoopRawMutex, ButtonEvent, 4>,
-) {
+async fn button_waiter(mut button: ExtiInput<'static, PA0>) {
     const DOUBLE_CLICK_DELAY: u64 = 250;
     const HOLD_DELAY: u64 = 1000;
 
@@ -150,9 +145,7 @@ async fn button_waiter(
         .is_err()
         {
             info!("Hold");
-            if queue.send(ButtonEvent::Hold).await.is_err() {
-                break;
-            }
+            CHANNEL.send(ButtonEvent::Hold).await;
             button.wait_for_falling_edge().await;
         } else if with_timeout(
             Duration::from_millis(DOUBLE_CLICK_DELAY),
@@ -161,15 +154,11 @@ async fn button_waiter(
         .await
         .is_err()
         {
-            if queue.send(ButtonEvent::SingleClick).await.is_err() {
-                break;
-            }
             info!("Single click");
+            CHANNEL.send(ButtonEvent::SingleClick).await;
         } else {
             info!("Double click");
-            if queue.send(ButtonEvent::DoubleClick).await.is_err() {
-                break;
-            }
+            CHANNEL.send(ButtonEvent::DoubleClick).await;
             button.wait_for_falling_edge().await;
         }
         button.wait_for_rising_edge().await;
diff --git a/examples/stm32h7/src/bin/usart_split.rs b/examples/stm32h7/src/bin/usart_split.rs
index ee1763aa4..40a7c3e44 100644
--- a/examples/stm32h7/src/bin/usart_split.rs
+++ b/examples/stm32h7/src/bin/usart_split.rs
@@ -4,10 +4,9 @@
 
 use defmt::*;
 use defmt_rtt as _; // global logger
-use embassy::blocking_mutex::raw::NoopRawMutex;
-use embassy::channel::mpsc::{self, Channel, Sender};
+use embassy::blocking_mutex::raw::ThreadModeRawMutex;
+use embassy::channel::channel::Channel;
 use embassy::executor::Spawner;
-use embassy::util::Forever;
 use embassy_stm32::dma::NoDma;
 use embassy_stm32::{
     peripherals::{DMA1_CH1, UART7},
@@ -28,7 +27,7 @@ async fn writer(mut usart: Uart<'static, UART7, NoDma, NoDma>) {
     }
 }
 
-static CHANNEL: Forever<Channel<NoopRawMutex, [u8; 8], 1>> = Forever::new();
+static CHANNEL: Channel<ThreadModeRawMutex, [u8; 8], 1> = Channel::new();
 
 #[embassy::main]
 async fn main(spawner: Spawner, p: Peripherals) -> ! {
@@ -40,28 +39,21 @@ async fn main(spawner: Spawner, p: Peripherals) -> ! {
 
     let (mut tx, rx) = usart.split();
 
-    let c = CHANNEL.put(Channel::new());
-    let (s, mut r) = mpsc::split(c);
-
-    unwrap!(spawner.spawn(reader(rx, s)));
+    unwrap!(spawner.spawn(reader(rx)));
 
     loop {
-        if let Some(buf) = r.recv().await {
-            info!("writing...");
-            unwrap!(tx.write(&buf).await);
-        }
+        let buf = CHANNEL.recv().await;
+        info!("writing...");
+        unwrap!(tx.write(&buf).await);
     }
 }
 
 #[embassy::task]
-async fn reader(
-    mut rx: UartRx<'static, UART7, DMA1_CH1>,
-    s: Sender<'static, NoopRawMutex, [u8; 8], 1>,
-) {
+async fn reader(mut rx: UartRx<'static, UART7, DMA1_CH1>) {
     let mut buf = [0; 8];
     loop {
         info!("reading...");
         unwrap!(rx.read(&mut buf).await);
-        unwrap!(s.send(buf).await);
+        CHANNEL.send(buf).await;
     }
 }