examples/idle-wfi.rs


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//! examples/idle-wfi.rs

#![deny(unsafe_code)]
#![deny(warnings)]
#![no_main]
#![no_std]

use panic_semihosting as _;

#[rtic::app(device = lm3s6965)]
mod app {
    use cortex_m_semihosting::{debug, hprintln};

    #[shared]
    struct Shared {}

    #[local]
    struct Local {}

    #[init]
    fn init(mut cx: init::Context) -> (Shared, Local, init::Monotonics) {
        hprintln!("init").unwrap();

        // Set the ARM SLEEPONEXIT bit to go to sleep after handling interrupts
        // See https://developer.arm.com/docs/100737/0100/power-management/sleep-mode/sleep-on-exit-bit
        cx.core.SCB.set_sleepdeep();

        (Shared {}, Local {}, init::Monotonics())
    }

    #[idle(local = [x: u32 = 0])]
    fn idle(cx: idle::Context) -> ! {
        // Locals in idle have lifetime 'static
        let _x: &'static mut u32 = cx.local.x;

        hprintln!("idle").unwrap();

        debug::exit(debug::EXIT_SUCCESS); // Exit QEMU simulator

        loop {
            // Now Wait For Interrupt is used instead of a busy-wait loop
            // to allow MCU to sleep between interrupts
            // https://developer.arm.com/documentation/ddi0406/c/Application-Level-Architecture/Instruction-Details/Alphabetical-list-of-instructions/WFI
            rtic::export::wfi()
        }
    }
}