rtic/stable/book/en/by-example/app_minimal.html
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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 affix "><li class="spacer"></li><li class="chapter-item expanded "><a href="../starting_a_project.html"><strong aria-hidden="true">1.</strong> Starting a new project</a></li><li class="chapter-item expanded "><a href="../by-example.html"><strong aria-hidden="true">2.</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">2.1.</strong> The app</a></li><li class="chapter-item expanded "><a href="../by-example/hardware_tasks.html"><strong aria-hidden="true">2.2.</strong> Hardware tasks</a></li><li class="chapter-item expanded "><a href="../by-example/software_tasks.html"><strong aria-hidden="true">2.3.</strong> Software tasks & spawn</a></li><li class="chapter-item expanded "><a href="../by-example/resources.html"><strong aria-hidden="true">2.4.</strong> Resources</a></li><li class="chapter-item expanded "><a href="../by-example/app_init.html"><strong aria-hidden="true">2.5.</strong> The init task</a></li><li class="chapter-item expanded "><a href="../by-example/app_idle.html"><strong aria-hidden="true">2.6.</strong> The idle task</a></li><li class="chapter-item expanded "><a href="../by-example/channel.html"><strong aria-hidden="true">2.7.</strong> Channel based communication</a></li><li class="chapter-item expanded "><a href="../by-example/delay.html"><strong aria-hidden="true">2.8.</strong> Delay and Timeout using Monotonics</a></li><li class="chapter-item expanded "><a href="../by-example/app_minimal.html" class="active"><strong aria-hidden="true">2.9.</strong> The minimal app</a></li><li class="chapter-item expanded "><a href="../by-example/tips/index.html"><strong aria-hidden="true">2.10.</strong> Tips & Tricks</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../by-example/tips/destructureing.html"><strong aria-hidden="true">2.10.1.</strong> Resource de-structure-ing</a></li><li class="chapter-item expanded "><a href="../by-example/tips/indirection.html"><strong aria-hidden="true">2.10.2.</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">2.10.3.</strong> 'static super-powers</a></li><li class="chapter-item expanded "><a href="../by-example/tips/view_code.html"><strong aria-hidden="true">2.10.4.</strong> Inspecting generated code</a></li></ol></li></ol></li><li class="chapter-item expanded "><a href="../monotonic_impl.html"><strong aria-hidden="true">3.</strong> Monotonics & the Timer Queue</a></li><li class="chapter-item expanded "><a href="../rtic_vs.html"><strong aria-hidden="true">4.</strong> RTIC vs. the world</a></li><li class="chapter-item expanded "><a href="../rtic_and_embassy.html"><strong aria-hidden="true">5.</strong> RTIC and Embassy</a></li><li class="chapter-item expanded "><a href="../awesome_rtic.html"><strong aria-hidden="true">6.</strong> Awesome RTIC examples</a></li><li class="chapter-item expanded affix "><li class="spacer"></li><li class="chapter-item expanded "><a href="../migration_v1_v2.html"><strong aria-hidden="true">7.</strong> Migrating from v1.0.x to v2.0.0</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../migration_v1_v2/monotonics.html"><strong aria-hidden="true">7.1.</strong> Migrating to rtic-monotonics</a></li><li class="chapter-item expanded "><a href="../migration_v1_v2/async_tasks.html"><strong aria-hidden="true">7.2.</strong> Software tasks must now be async</a></li><li class="chapter-item expanded "><a href="../migration_v1_v2/rtic-sync.html"><strong aria-hidden="true">7.3.</strong> Using and understanding rtic-sync</a></li><li class="chapter-item expanded "><a href="../migration_v1_v2/complete_example.html"><strong aria-hidden="true">7.4.</strong> A code example on migration</a></li></ol></li><li class="chapter-item expanded "><li class="spacer"></li><li class="chapter-item expanded "><a href="../internals.html"><strong aria-hidden="true">8.</strong> Under the hood</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../internals/targets.html"><strong aria-hidden="true">8.1.</strong> Cortex-M architectures</a></li></ol></li></ol>
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<h1 class="menu-title">Real-Time Interrupt-driven Concurrency</h1>
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<h1 id="the-minimal-app"><a class="header" href="#the-minimal-app">The minimal app</a></h1>
<p>This is the smallest possible RTIC application:</p>
<pre><code class="language-rust noplayground">//! examples/smallest.rs
#![no_main]
#![no_std]
#![deny(warnings)]
#![deny(unsafe_code)]
#![deny(missing_docs)]
use panic_semihosting as _; // panic handler
use rtic::app;
#[app(device = lm3s6965)]
mod app {
use cortex_m_semihosting::debug;
#[shared]
struct Shared {}
#[local]
struct Local {}
#[init]
fn init(_: init::Context) -&gt; (Shared, Local) {
debug::exit(debug::EXIT_SUCCESS); // Exit QEMU simulator
(Shared {}, Local {})
}
}</code></pre>
<p>RTIC is designed with resource efficiency in mind. RTIC itself does not rely on any dynamic memory allocation, thus RAM requirement is dependent only on the application. The flash memory footprint is below 1kB including the interrupt vector table.</p>
<p>For a minimal example you can expect something like:</p>
<pre><code class="language-console">$ cargo size --example smallest --target thumbv7m-none-eabi --release
</code></pre>
<pre><code class="language-console">Finished release [optimized] target(s) in 0.07s
text data bss dec hex filename
924 0 0 924 39c smallest
</code></pre>
<!-- ---
Technically, RTIC will generate a statically allocated future for each *software* task (holding the execution context, including the `Context` struct and stack allocated variables). Futures associated to the same static priority will share an asynchronous stack during execution. -->
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