Multi Producer Single Consumer channel

An MPSC inspired by Tokio and Crossbeam. The MPSC is designed to support both single and multi core processors, with only single core implemented at this time. The allocation of the channel’s buffer is inspired by the const generic parameters that Heapless provides.

examples/nrf/src/bin/mpsc.rs

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+#![no_std]
+#![no_main]
+#![feature(min_type_alias_impl_trait)]
+#![feature(impl_trait_in_bindings)]
+#![feature(type_alias_impl_trait)]
+#![allow(incomplete_features)]
+
+#[path = "../example_common.rs"]
+mod example_common;
+
+use defmt::panic;
+use embassy::executor::Spawner;
+use embassy::time::{Duration, Timer};
+use embassy::util::mpsc::TryRecvError;
+use embassy::util::{mpsc, Forever};
+use embassy_nrf::gpio::{Level, Output, OutputDrive};
+use embassy_nrf::Peripherals;
+use embedded_hal::digital::v2::OutputPin;
+use mpsc::{Channel, Sender, WithThreadModeOnly};
+
+enum LedState {
+    On,
+    Off,
+}
+
+static CHANNEL: Forever<Channel<WithThreadModeOnly, LedState, 1>> = Forever::new();
+
+#[embassy::task(pool_size = 1)]
+async fn my_task(sender: Sender<'static, WithThreadModeOnly, 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::with_thread_mode_only());
+    let (sender, mut receiver) = mpsc::split(channel);
+
+    spawner.spawn(my_task(sender)).unwrap();
+
+    // 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().unwrap(),
+            Some(LedState::Off) => led.set_low().unwrap(),
+            _ => (),
+        }
+    }
+}