diff --git a/examples/stm32f0/src/bin/priority.rs b/examples/stm32f0/src/bin/priority.rs new file mode 100644 index 00000000..7fed6a77 --- /dev/null +++ b/examples/stm32f0/src/bin/priority.rs @@ -0,0 +1,139 @@ +//! 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] +#![feature(type_alias_impl_trait)] + +use cortex_m_rt::entry; +use defmt::*; +use embassy_stm32::executor::{Executor, InterruptExecutor}; +use embassy_stm32::interrupt; +use embassy_stm32::interrupt::InterruptExt; +use embassy_time::{Duration, 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(Duration::from_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(Duration::from_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(Duration::from_ticks(32983)).await; + } +} + +static EXECUTOR_HIGH: StaticCell> = StaticCell::new(); +static EXECUTOR_MED: StaticCell> = StaticCell::new(); +static EXECUTOR_LOW: StaticCell = StaticCell::new(); + +#[entry] +fn main() -> ! { + // Initialize and create handle for devicer peripherals + let _p = embassy_stm32::init(Default::default()); + + // High-priority executor: USART1, priority level 6 + let irq = interrupt::take!(USART1); + irq.set_priority(interrupt::Priority::P6); + let executor = EXECUTOR_HIGH.init(InterruptExecutor::new(irq)); + let spawner = executor.start(); + unwrap!(spawner.spawn(run_high())); + + // Medium-priority executor: USART2, priority level 7 + let irq = interrupt::take!(USART2); + irq.set_priority(interrupt::Priority::P7); + let executor = EXECUTOR_MED.init(InterruptExecutor::new(irq)); + let spawner = executor.start(); + 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())); + }); +}