Crate minimult_cortex_m

This crate for Rust provides a minimal multitask library Minimult for Cortex-M microcontrollers.

Target

Single-core systems of

• Cortex-M0 / M0+ / M1 (thumbv6m-none-eabi)
• Cortex-M3 (thumbv7m-none-eabi)
• Cortex-M4 / M7 (thumbv7em-none-eabi)
• Cortex-M4 / M7 with FPU (thumbv7em-none-eabihf)
• Cortex-M23 (thumbv8m.base-none-eabi)
• Cortex-M33 / M35P (thumbv8m.main-none-eabi)

Minimult is still in beta because the author had only a few tests only on Cortex-M4 with FPU.

Features

• Task like that of a typical RTOS
  • Minimult can take closures and register them as tasks.
  • Minimult runs into a loop to start dispatching those tasks.
    • Not supported: dynamically creating and spawning.
• Synchronization
  • idle and kick
    • A task goes into an idle state and other tasks/interrupts wake it up by kicking.
  • MTMsgSender and MTMsgReceiver
    • Task-to-task communication by message passing.
• Priority-based dispatching
  • A higher priority task preempts lower priority tasks.
  • Round-robin dispatching within the same priority tasks.
  • dispatch can be directly requested so that timer-based preemption is also possible.
• Static memory allocation
  • Minimult doesn't require a global allocator but reserves a bunch of memory block in advance.

Examples

Usage Outline

#![no_main]
#![no_std]

use cortex_m::Peripherals;
use cortex_m_rt::entry;
use cortex_m_rt::exception;
extern crate panic_semihosting;

// other codes...

use minimult_cortex_m::*;

#[entry]
fn main() -> ! {
    let mut mem = Minimult::mem::<[u8; 4096]>();
    let mut mt = Minimult::new(&mut mem, 2);

    // other codes...

    let mut q = mt.msgq::<u32>(4);
    let (snd, rcv) = q.ch();

    mt.register(0/*tid*/, 1, 256, || task0(snd));
    mt.register(1/*tid*/, 1, 256, || task1(rcv));

    // other codes...

    let cmperi = Peripherals::take().unwrap();
    let mut syst = cmperi.SYST;
    syst.set_clock_source(cortex_m::peripheral::syst::SystClkSource::Core);
    syst.set_reload(0xffffff);
    syst.clear_current();
    syst.enable_counter();
    syst.enable_interrupt();

    // other codes...

    mt.run()
}

#[exception]
fn SysTick()
{
    // other codes...

    Minimult::kick(0/*tid*/);
}

fn task0(snd: MTMsgSender<u32>)
{
    // other codes...

    loop {
        Minimult::idle();

        // other codes...

        let some_value = 1;
        snd.send(some_value);
    }
}

fn task1(rcv: MTMsgReceiver<u32>)
{
    // other codes...

    loop {
        let mut some_value = 0;
        rcv.receive(|v| {some_value = *v});

        // other codes...
    }
}

Other Examples

You can find a specific board's example here. Currently there are very few examples, however.

Structs

MTMemBlk	Memory block used by Minimult
MTMsgQueue	Message queue for task-to-task communication
MTMsgReceiver	Message receiving channel
MTMsgSender	Message sending channel
Minimult	Multitasking API

Type Definitions

MTTaskId	Task identifier
MTTaskPri	Task priority