107 lines
4.0 KiB
Rust
107 lines
4.0 KiB
Rust
#![no_std]
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#![no_main]
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#![feature(type_alias_impl_trait)]
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use defmt::unwrap;
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use embassy_executor::executor::Spawner;
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use embassy_executor::time::{Duration, Timer};
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use embassy_util::blocking_mutex::raw::ThreadModeRawMutex;
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use embassy_util::channel::pubsub::{DynSubscriber, PubSubChannel, Subscriber};
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use {defmt_rtt as _, panic_probe as _};
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/// Create the message bus. It has a queue of 4, supports 3 subscribers and 1 publisher
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static MESSAGE_BUS: PubSubChannel<ThreadModeRawMutex, Message, 4, 3, 1> = PubSubChannel::new();
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#[derive(Clone, defmt::Format)]
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enum Message {
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A,
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B,
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C,
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}
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#[embassy_executor::main]
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async fn main(spawner: Spawner, _p: embassy_nrf::Peripherals) {
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defmt::info!("Hello World!");
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// It's good to set up the subscribers before publishing anything.
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// A subscriber will only yield messages that have been published after its creation.
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spawner.must_spawn(fast_logger(unwrap!(MESSAGE_BUS.subscriber())));
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spawner.must_spawn(slow_logger(unwrap!(MESSAGE_BUS.dyn_subscriber())));
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spawner.must_spawn(slow_logger_pure(unwrap!(MESSAGE_BUS.dyn_subscriber())));
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// Get a publisher
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let message_publisher = unwrap!(MESSAGE_BUS.publisher());
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// We can't get more (normal) publishers
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// We can have an infinite amount of immediate publishers. They can't await a publish, only do an immediate publish
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defmt::assert!(MESSAGE_BUS.publisher().is_err());
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let mut index = 0;
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loop {
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Timer::after(Duration::from_millis(500)).await;
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let message = match index % 3 {
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0 => Message::A,
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1 => Message::B,
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2..=u32::MAX => Message::C,
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};
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// We publish immediately and don't await anything.
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// If the queue is full, it will cause the oldest message to not be received by some/all subscribers
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message_publisher.publish_immediate(message);
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// Try to comment out the last one and uncomment this line below.
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// The behaviour will change:
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// - The subscribers won't miss any messages any more
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// - Trying to publish now has some wait time when the queue is full
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// message_publisher.publish(message).await;
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index += 1;
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}
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}
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/// A logger task that just awaits the messages it receives
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///
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/// This takes the generic `Subscriber`. This is most performant, but requires you to write down all of the generics
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#[embassy_executor::task]
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async fn fast_logger(mut messages: Subscriber<'static, ThreadModeRawMutex, Message, 4, 3, 1>) {
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loop {
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let message = messages.next_message().await;
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defmt::info!("Received message at fast logger: {:?}", message);
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}
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}
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/// A logger task that awaits the messages, but also does some other work.
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/// Because of this, depeding on how the messages were published, the subscriber might miss some messages
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///
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/// This takes the dynamic `DynSubscriber`. This is not as performant as the generic version, but let's you ignore some of the generics
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#[embassy_executor::task]
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async fn slow_logger(mut messages: DynSubscriber<'static, Message>) {
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loop {
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// Do some work
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Timer::after(Duration::from_millis(2000)).await;
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// If the publisher has used the `publish_immediate` function, then we may receive a lag message here
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let message = messages.next_message().await;
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defmt::info!("Received message at slow logger: {:?}", message);
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// If the previous one was a lag message, then we should receive the next message here immediately
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let message = messages.next_message().await;
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defmt::info!("Received message at slow logger: {:?}", message);
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}
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}
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/// Same as `slow_logger` but it ignores lag results
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#[embassy_executor::task]
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async fn slow_logger_pure(mut messages: DynSubscriber<'static, Message>) {
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loop {
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// Do some work
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Timer::after(Duration::from_millis(2000)).await;
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// Instead of receiving lags here, we just ignore that and read the next message
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let message = messages.next_message_pure().await;
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defmt::info!("Received message at slow logger pure: {:?}", message);
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}
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}
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