rtic/book/en/src/migration/migration_v4.md

Migrating from v0.4.x to v0.5.0

This section covers how to upgrade an application written against RTIC v0.4.x to the version v0.5.0 of the framework.

Cargo.toml

First, the version of the cortex-m-rtic dependency needs to be updated to "0.5.0". The timer-queue feature needs to be removed.

[dependencies.cortex-m-rtic]
# change this
version = "0.4.3"

# into this
version = "0.5.0"

# and remove this Cargo feature
features = ["timer-queue"]
#           ^^^^^^^^^^^^^

Context argument

All functions inside the #[rtic::app] item need to take as first argument a Context structure. This Context type will contain the variables that were magically injected into the scope of the function by version v0.4.x of the framework: resources, spawn, schedule -- these variables will become fields of the Context structure. Each function within the #[rtic::app] item gets a different Context type.

#[rtic::app(/* .. */)]
const APP: () = {
    // change this
    #[task(resources = [x], spawn = [a], schedule = [b])]
    fn foo() {
        resources.x.lock(|x| /* .. */);
        spawn.a(message);
        schedule.b(baseline);
    }

    // into this
    #[task(resources = [x], spawn = [a], schedule = [b])]
    fn foo(mut cx: foo::Context) {
        // ^^^^^^^^^^^^^^^^^^^^

        cx.resources.x.lock(|x| /* .. */);
    //  ^^^

        cx.spawn.a(message);
    //  ^^^

        cx.schedule.b(message, baseline);
    //  ^^^
    }

    // change this
    #[init]
    fn init() {
        // ..
    }

    // into this
    #[init]
    fn init(cx: init::Context) {
        //  ^^^^^^^^^^^^^^^^^
        // ..
    }

    // ..
};

Resources

The syntax used to declare resources has been changed from static mut variables to a struct Resources.

#[rtic::app(/* .. */)]
const APP: () = {
    // change this
    static mut X: u32 = 0;
    static mut Y: u32 = (); // late resource

    // into this
    struct Resources {
        #[init(0)] // <- initial value
        X: u32, // NOTE: we suggest changing the naming style to `snake_case`

        Y: u32, // late resource
    }

    // ..
};

Device peripherals

If your application was accessing the device peripherals in #[init] through the device variable then you'll need to add peripherals = true to the #[rtic::app] attribute to continue to access the device peripherals through the device field of the init::Context structure.

Change this:

#[rtic::app(/* .. */)]
const APP: () = {
    #[init]
    fn init() {
        device.SOME_PERIPHERAL.write(something);
    }

    // ..
};

Into this:

#[rtic::app(/* .. */, peripherals = true)]
//                    ^^^^^^^^^^^^^^^^^^
const APP: () = {
    #[init]
    fn init(cx: init::Context) {
        //  ^^^^^^^^^^^^^^^^^
        cx.device.SOME_PERIPHERAL.write(something);
    //  ^^^
    }

    // ..
};

#[interrupt] and #[exception]

The #[interrupt] and #[exception] attributes have been removed. To declare hardware tasks in v0.5.x use the #[task] attribute with the binds argument.

Change this:

#[rtic::app(/* .. */)]
const APP: () = {
    // hardware tasks
    #[exception]
    fn SVCall() { /* .. */ }

    #[interrupt]
    fn UART0() { /* .. */ }

    // software task
    #[task]
    fn foo() { /* .. */ }

    // ..
};

Into this:

#[rtic::app(/* .. */)]
const APP: () = {
    #[task(binds = SVCall)]
    //     ^^^^^^^^^^^^^^
    fn svcall(cx: svcall::Context) { /* .. */ }
    // ^^^^^^ we suggest you use a `snake_case` name here

    #[task(binds = UART0)]
    //     ^^^^^^^^^^^^^
    fn uart0(cx: uart0::Context) { /* .. */ }

    #[task]
    fn foo(cx: foo::Context) { /* .. */ }

    // ..
};

schedule

The timer-queue feature has been removed. To use the schedule API one must first define the monotonic timer the runtime will use using the monotonic argument of the #[rtic::app] attribute. To continue using the cycle counter (CYCCNT) as the monotonic timer, and match the behavior of version v0.4.x, add the monotonic = rtic::cyccnt::CYCCNT argument to the #[rtic::app] attribute.

Also, the Duration and Instant types and the U32Ext trait have been moved into the rtic::cyccnt module. This module is only available on ARMv7-M+ devices. The removal of the timer-queue also brings back the DWT peripheral inside the core peripherals struct, this will need to be enabled by the application inside init.

Change this:

use rtic::{Duration, Instant, U32Ext};

#[rtic::app(/* .. */)]
const APP: () = {
    #[task(schedule = [b])]
    fn a() {
        // ..
    }
};

Into this:

use rtic::cyccnt::{Duration, Instant, U32Ext};
//        ^^^^^^^^

#[rtic::app(/* .. */, monotonic = rtic::cyccnt::CYCCNT)]
//                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
const APP: () = {
    #[init]
    fn init(cx: init::Context) {
        cx.core.DWT.enable_cycle_counter();
        // optional, configure the DWT run without a debugger connected
        cx.core.DCB.enable_trace();
    }
    #[task(schedule = [b])]
    fn a(cx: a::Context) {
        // ..
    }
};