embassy/examples/stm32f0/src/bin/multiprio.rs

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//! This example showcases how to create multiple Executor instances to run tasks at
//! different priority levels.
//!
//! Low priority executor runs in thread mode (not interrupt), and uses `sev` for signaling
//! there's work in the queue, and `wfe` for waiting for work.
//!
//! Medium and high priority executors run in two interrupts with different priorities.
//! Signaling work is done by pending the interrupt. No "waiting" needs to be done explicitly, since
//! when there's work the interrupt will trigger and run the executor.
//!
//! Sample output below. Note that high priority ticks can interrupt everything else, and
//! medium priority computations can interrupt low priority computations, making them to appear
//! to take significantly longer time.
//!
//! ```not_rust
//! [med] Starting long computation
//! [med] done in 992 ms
//! [high] tick!
//! [low] Starting long computation
//! [med] Starting long computation
//! [high] tick!
//! [high] tick!
//! [med] done in 993 ms
//! [med] Starting long computation
//! [high] tick!
//! [high] tick!
//! [med] done in 993 ms
//! [low] done in 3972 ms
//! [med] Starting long computation
//! [high] tick!
//! [high] tick!
//! [med] done in 993 ms
//! ```
//!
//! For comparison, try changing the code so all 3 tasks get spawned on the low priority executor.
//! You will get an output like the following. Note that no computation is ever interrupted.
//!
//! ```not_rust
//! [high] tick!
//! [med] Starting long computation
//! [med] done in 496 ms
//! [low] Starting long computation
//! [low] done in 992 ms
//! [med] Starting long computation
//! [med] done in 496 ms
//! [high] tick!
//! [low] Starting long computation
//! [low] done in 992 ms
//! [high] tick!
//! [med] Starting long computation
//! [med] done in 496 ms
//! [high] tick!
//! ```
//!
#![no_std]
#![no_main]
use cortex_m_rt::entry;
use defmt::*;
use embassy_executor::{Executor, InterruptExecutor};
use embassy_stm32::interrupt;
use embassy_stm32::interrupt::{InterruptExt, Priority};
use embassy_time::{Instant, Timer};
use static_cell::StaticCell;
use {defmt_rtt as _, panic_probe as _};
#[embassy_executor::task]
async fn run_high() {
loop {
// info!(" [high] tick!");
Timer::after_ticks(27374).await;
}
}
#[embassy_executor::task]
async fn run_med() {
loop {
let start = Instant::now();
info!(" [med] Starting long computation");
// Spin-wait to simulate a long CPU computation
cortex_m::asm::delay(8_000_000); // ~1 second
let end = Instant::now();
let ms = end.duration_since(start).as_ticks() / 33;
info!(" [med] done in {} ms", ms);
Timer::after_ticks(23421).await;
}
}
#[embassy_executor::task]
async fn run_low() {
loop {
let start = Instant::now();
info!("[low] Starting long computation");
// Spin-wait to simulate a long CPU computation
cortex_m::asm::delay(16_000_000); // ~2 seconds
let end = Instant::now();
let ms = end.duration_since(start).as_ticks() / 33;
info!("[low] done in {} ms", ms);
Timer::after_ticks(32983).await;
}
}
static EXECUTOR_HIGH: InterruptExecutor = InterruptExecutor::new();
static EXECUTOR_MED: InterruptExecutor = InterruptExecutor::new();
static EXECUTOR_LOW: StaticCell<Executor> = StaticCell::new();
#[interrupt]
unsafe fn USART1() {
EXECUTOR_HIGH.on_interrupt()
}
#[interrupt]
unsafe fn USART2() {
EXECUTOR_MED.on_interrupt()
}
#[entry]
fn main() -> ! {
// Initialize and create handle for devicer peripherals
let _p = embassy_stm32::init(Default::default());
// STM32s dont have any interrupts exclusively for software use, but they can all be triggered by software as well as
// by the peripheral, so we can just use any free interrupt vectors which arent used by the rest of your application.
// In this case were using UART1 and UART2, but theres nothing special about them. Any otherwise unused interrupt
// vector would work exactly the same.
// High-priority executor: USART1, priority level 6
interrupt::USART1.set_priority(Priority::P6);
let spawner = EXECUTOR_HIGH.start(interrupt::USART1);
unwrap!(spawner.spawn(run_high()));
// Medium-priority executor: USART2, priority level 7
interrupt::USART2.set_priority(Priority::P7);
let spawner = EXECUTOR_MED.start(interrupt::USART2);
unwrap!(spawner.spawn(run_med()));
// Low priority executor: runs in thread mode, using WFE/SEV
let executor = EXECUTOR_LOW.init(Executor::new());
executor.run(|spawner| {
unwrap!(spawner.spawn(run_low()));
});
}