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<ol class="chapter"><li class="chapter-item expanded affix "><a href="../preface.html">Preface</a></li><li class="chapter-item expanded "><a href="../by-example.html"><strong aria-hidden="true">1.</strong> RTIC by example</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../by-example/app.html"><strong aria-hidden="true">1.1.</strong> The app</a></li><li class="chapter-item expanded "><a href="../by-example/resources.html"><strong aria-hidden="true">1.2.</strong> Resources</a></li><li class="chapter-item expanded "><a href="../by-example/app_init.html"><strong aria-hidden="true">1.3.</strong> The init task</a></li><li class="chapter-item expanded "><a href="../by-example/app_idle.html"><strong aria-hidden="true">1.4.</strong> The idle task</a></li><li class="chapter-item expanded "><a href="../by-example/app_task.html"><strong aria-hidden="true">1.5.</strong> Defining tasks</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../by-example/hardware_tasks.html" class="active"><strong aria-hidden="true">1.5.1.</strong> Hardware tasks</a></li><li class="chapter-item expanded "><a href="../by-example/software_tasks.html"><strong aria-hidden="true">1.5.2.</strong> Software tasks & spawn</a></li><li class="chapter-item expanded "><a href="../by-example/message_passing.html"><strong aria-hidden="true">1.5.3.</strong> Message passing & capacity</a></li><li class="chapter-item expanded "><a href="../by-example/app_priorities.html"><strong aria-hidden="true">1.5.4.</strong> Task priorities</a></li><li class="chapter-item expanded "><a href="../by-example/monotonic.html"><strong aria-hidden="true">1.5.5.</strong> Monotonic & spawn_{at/after}</a></li></ol></li><li class="chapter-item expanded "><a href="../by-example/starting_a_project.html"><strong aria-hidden="true">1.6.</strong> Starting a new project</a></li><li class="chapter-item expanded "><a href="../by-example/app_minimal.html"><strong aria-hidden="true">1.7.</strong> The minimal app</a></li><li class="chapter-item expanded "><a href="../by-example/tips.html"><strong aria-hidden="true">1.8.</strong> Tips & Tricks</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../by-example/tips_monotonic_impl.html"><strong aria-hidden="true">1.8.1.</strong> Implementing Monotonic</a></li><li class="chapter-item expanded "><a href="../by-example/tips_destructureing.html"><strong aria-hidden="true">1.8.2.</strong> Resource de-structure-ing</a></li><li class="chapter-item expanded "><a href="../by-example/tips_indirection.html"><strong aria-hidden="true">1.8.3.</strong> Avoid copies when message passing</a></li><li class="chapter-item expanded "><a href="../by-example/tips_static_lifetimes.html"><strong aria-hidden="true">1.8.4.</strong> 'static super-powers</a></li><li class="chapter-item expanded "><a href="../by-example/tips_view_code.html"><strong aria-hidden="true">1.8.5.</strong> Inspecting generated code</a></li><li class="chapter-item expanded "><a href="../by-example/tips_from_ram.html"><strong aria-hidden="true">1.8.6.</strong> Running tasks from RAM</a></li></ol></li></ol></li><li class="chapter-item expanded "><a href="../awesome_rtic.html"><strong aria-hidden="true">2.</strong> Awesome RTIC examples</a></li><li class="chapter-item expanded "><a href="../migration.html"><strong aria-hidden="true">3.</strong> Migration Guides</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../migration/migration_v5.html"><strong aria-hidden="true">3.1.</strong> v0.5.x to v1.0.x</a></li><li class="chapter-item expanded "><a href="../migration/migration_v4.html"><strong aria-hidden="true">3.2.</strong> v0.4.x to v0.5.x</a></li><li class="chapter-item expanded "><a href="../migration/migration_rtic.html"><strong aria-hidden="true">3.3.</strong> RTFM to RTIC</a></li></ol></li><li class="chapter-item expanded "><a href="../internals.html"><strong aria-hidden="true">4.</strong> Under the hood</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../internals/targ
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<h1 class="menu-title">Real-Time Interrupt-driven Concurrency</h1>
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<main>
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<h1 id="hardware-tasks"><a class="header" href="#hardware-tasks">Hardware tasks</a></h1>
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<p>At its core RTIC is using a hardware interrupt controller (<a href="https://developer.arm.com/documentation/100166/0001/Nested-Vectored-Interrupt-Controller/NVIC-functional-description/NVIC-interrupts">ARM NVIC on cortex-m</a>)
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to schedule and start execution of tasks. All tasks except <code>pre-init</code>, <code>#[init]</code> and <code>#[idle]</code>
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run as interrupt handlers.</p>
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<p>Hardware tasks are explicitly bound to interrupt handlers.</p>
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<p>To bind a task to an interrupt, use the <code>#[task]</code> attribute argument <code>binds = InterruptName</code>.
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This task then becomes the interrupt handler for this hardware interrupt vector.</p>
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<p>All tasks bound to an explicit interrupt are called <em>hardware tasks</em> since they
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start execution in reaction to a hardware event.</p>
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<p>Specifying a non-existing interrupt name will cause a compilation error. The interrupt names
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are commonly defined by <a href="https://docs.rust-embedded.org/book/start/registers.html">PAC or HAL</a> crates.</p>
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<p>Any available interrupt vector should work. Specific devices may bind
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specific interrupt priorities to specific interrupt vectors outside
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user code control. See for example the
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<a href="https://github.com/rtic-rs/cortex-m-rtic/issues/434">nRF “softdevice”</a>.</p>
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<p>Beware of using interrupt vectors that are used internally by hardware features;
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RTIC is unaware of such hardware specific details.</p>
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<p>The example below demonstrates the use of the <code>#[task(binds = InterruptName)]</code> attribute to declare a
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hardware task bound to an interrupt handler.</p>
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<pre><pre class="playground"><code class="language-rust"><span class="boring">#![allow(unused)]
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</span><span class="boring">fn main() {
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</span>//! examples/hardware.rs
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#![deny(unsafe_code)]
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#![deny(warnings)]
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#![deny(missing_docs)]
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#![no_main]
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#![no_std]
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use panic_semihosting as _;
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#[rtic::app(device = lm3s6965)]
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mod app {
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use cortex_m_semihosting::{debug, hprintln};
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use lm3s6965::Interrupt;
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#[shared]
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struct Shared {}
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#[local]
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struct Local {}
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#[init]
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fn init(_: init::Context) -> (Shared, Local, init::Monotonics) {
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// Pends the UART0 interrupt but its handler won't run until *after*
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// `init` returns because interrupts are disabled
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rtic::pend(Interrupt::UART0); // equivalent to NVIC::pend
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hprintln!("init");
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(Shared {}, Local {}, init::Monotonics())
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}
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#[idle]
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fn idle(_: idle::Context) -> ! {
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// interrupts are enabled again; the `UART0` handler runs at this point
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hprintln!("idle");
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rtic::pend(Interrupt::UART0);
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loop {
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// Exit moved after nop to ensure that rtic::pend gets
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// to run before exiting
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cortex_m::asm::nop();
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debug::exit(debug::EXIT_SUCCESS); // Exit QEMU simulator
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}
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}
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#[task(binds = UART0, local = [times: u32 = 0])]
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fn uart0(cx: uart0::Context) {
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// Safe access to local `static mut` variable
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*cx.local.times += 1;
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hprintln!(
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"UART0 called {} time{}",
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*cx.local.times,
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if *cx.local.times > 1 { "s" } else { "" }
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);
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}
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}
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<span class="boring">}</span></code></pre></pre>
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<pre><code class="language-console">$ cargo run --target thumbv7m-none-eabi --example hardware
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init
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UART0 called 1 time
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idle
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UART0 called 2 times
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</code></pre>
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