Module f3::examples::_09_cooperative

Cooperative multitasking

This programs runs the roulette and serial-echo examples as concurrent tasks using generators.

#![deny(unsafe_code)]
#![deny(warnings)]
#![feature(generator_trait)]
#![feature(generators)]
#![no_std]
 
extern crate cortex_m;
extern crate f3;
#[macro_use(await)]
extern crate nb;
 
use core::ops::Generator;
 
use f3::hal::prelude::*;
use f3::hal::serial::Serial;
use f3::hal::stm32f30x;
use f3::hal::timer::Timer;
use f3::led::Leds;
 
fn main() {
    let p = stm32f30x::Peripherals::take().unwrap();
 
    let mut flash = p.FLASH.constrain();
    let mut rcc = p.RCC.constrain();
    let gpioe = p.GPIOE.split(&mut rcc.ahb);
    let mut gpioa = p.GPIOA.split(&mut rcc.ahb);
 
    let clocks = rcc.cfgr.freeze(&mut flash.acr);
 
    let tx = gpioa.pa9.into_af7(&mut gpioa.moder, &mut gpioa.afrh);
    let rx = gpioa.pa10.into_af7(&mut gpioa.moder, &mut gpioa.afrh);
 
    let serial = Serial::usart1(p.USART1, (tx, rx), 115_200.bps(), clocks, &mut rcc.apb2);
    let (mut tx, mut rx) = serial.split();
 
    let mut leds: Leds = Leds::new(gpioe);
    // This timer, unlike `delay`, does *periodic* count downs at specified frequency (8 Hz)
    let mut timer = Timer::tim6(p.TIM6, 8.hz(), clocks, &mut rcc.apb1);
 
    // Tasks
    let mut roulette = || {
        let n = leds.len();
        loop {
            for curr in 0..n {
                let next = (curr + 1) % n;
                leds[curr].off();
                leds[next].on();
 
                // NOTE error type is `!`
                await!(timer.wait()).ok();
            }
        }
    };
 
    let mut echo = || {
        loop {
            let byte = await!(rx.read()).unwrap();
            // NOTE error type is `!`
            await!(tx.write(byte)).ok();
        }
    };
 
    // Run tasks cooperatively
    // When a task can't do any more progress it suspends it execution and the next task is resumed
    loop {
        roulette.resume();
        echo.resume();
    }
}