embassy #[main] convenience for RISC-V / Xtensa

[bjoernQ]

This makes the #[main] macro easily useable.

For RISC-V it just delegates to the existing macro and passes the entry.

For Xtensa it's basically an adaption of the code found in embassy-macro. Since we bring our own executor there it probably won't make sense to have it in embassy

For now, I haven't changed the examples - wanted to wait for a first review round

Here is the embassy_hello_world.rs adapted for S3:

//! embassy hello world
//!
//! This is an example of running the embassy executor with multiple tasks
//! concurrently.

#![no_std]
#![no_main]
#![feature(type_alias_impl_trait)]

use embassy_executor::Spawner;
use embassy_time::{Duration, Timer};
use esp32s3_hal::{
    clock::ClockControl,
    embassy::{self},
    peripherals::Peripherals,
    prelude::*,
};
use esp_backtrace as _;

#[embassy_executor::task]
async fn run1() {
    loop {
        esp_println::println!("Hello world from embassy using esp-hal-async!");
        Timer::after(Duration::from_millis(1_000)).await;
    }
}

#[embassy_executor::task]
async fn run2() {
    loop {
        esp_println::println!("Bing!");
        Timer::after(Duration::from_millis(5_000)).await;
    }
}

#[main]
async fn main(spawner: Spawner) {
    esp_println::println!("Init!");
    let peripherals = Peripherals::take();
    let system = peripherals.SYSTEM.split();
    let clocks = ClockControl::boot_defaults(system.clock_control).freeze();

    #[cfg(feature = "embassy-time-systick")]
    embassy::init(
        &clocks,
        esp32s3_hal::systimer::SystemTimer::new(peripherals.SYSTIMER),
    );

    #[cfg(feature = "embassy-time-timg0")]
    {
        let timer_group0 = esp32s3_hal::timer::TimerGroup::new(peripherals.TIMG0, &clocks);
        embassy::init(&clocks, timer_group0.timer0);
    }

    spawner.spawn(run1()).ok();
    spawner.spawn(run2()).ok();

    loop {
        esp_println::println!("Tada!");
        Timer::after(Duration::from_millis(1_500)).await;
    }
}

It's really just a convenience - the current way of creating and using an executor can still be used unchanged.

[bugadani]

I thought you must call embassy::init before creating the first executor. Won't this just immediately always panic because the executor can't allocate an alarm?

Nvm I checked now and I guess I just didn't understand how this works.

[MabezDev]

Nice, I've been meaning to do this for a while 😅. Looks good to me :)