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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"><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" class="active"><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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<h1 id="implementing-a-monotonic-timer-for-scheduling"><a class="header" href="#implementing-a-monotonic-timer-for-scheduling">Implementing a <code>Monotonic</code> timer for scheduling</a></h1>
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<p>The framework is flexible because it can use any timer which has compare-match and optionally
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supporting overflow interrupts for scheduling.
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The single requirement to make a timer usable with RTIC is implementing the
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<a href="https://docs.rs/rtic-monotonic/"><code>rtic_monotonic::Monotonic</code></a> trait.</p>
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<p>Implementing time counting that supports large time spans is generally <strong>difficult</strong>, in RTIC 0.5
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implementing time handling was a common problem.
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Moreover, the relation between time and timers used for scheduling was difficult to understand.</p>
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<p>For RTIC 1.0 we instead assume the user has a time library, e.g. <a href="https://docs.rs/fugit/"><code>fugit</code></a> or <a href="https://docs.rs/embedded_time/"><code>embedded_time</code></a>,
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as the basis for all time-based operations when implementing <code>Monotonic</code>.
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These libraries make it much easier to correctly implement the <code>Monotonic</code> trait, allowing the use of
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almost any timer in the system for scheduling.</p>
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<p>The trait documents the requirements for each method,
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and for inspiration here is a list of <code>Monotonic</code> implementations:</p>
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<ul>
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<li><a href="https://github.com/kalkyl/f411-rtic/blob/a696fce7d6d19fda2356c37642c4d53547982cca/src/mono.rs"><code>STM32F411 series</code></a>, implemented for the 32-bit timers</li>
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<li><a href="https://github.com/kalkyl/nrf-play/blob/47f4410d4e39374c18ff58dc17c25159085fb526/src/mono.rs"><code>Nordic nRF52 series Timer</code></a>, implemented for the 32-bit timers</li>
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<li><a href="https://gist.github.com/korken89/fe94a475726414dd1bce031c76adc3dd"><code>Nordic nRF52 series RTC</code></a>, implemented for the RTCs</li>
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<li><a href="https://github.com/rtic-rs/systick-monotonic"><code>Systick based</code></a>, runs at a fixed interrupt (tick) rate - with some overhead but simple and with support for large time spans</li>
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<li><a href="https://github.com/rtic-rs/dwt-systick-monotonic"><code>DWT and Systick based</code></a>, a more efficient (tickless) implementation - requires both <code>SysTick</code> and <code>DWT</code>, supports both high resolution and large time spans</li>
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</ul>
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<p>If you know of more implementations feel free to add them to this list.</p>
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