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