Simpler Channel.

- 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.

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(),
+        }
+    }
+}