https://blog.implrust.com • This is a web feed, also known as an Atom feed. Subscribe by copying the URL from the address bar into your newsreader. Visit About Feeds to learn more and get started. It's free. Visit website Recent posts Updated on $DATE date nrf52833 impl Blog for Rust - nrf52833 impl Rust Blog Posts Zola2026-08-25T00:00:00+00:00https://blog.implrust.com/tags/nrf52833/atom.xml Make the micro:bit's LED Matrix React to Sound with Rust 2026-08-25T00:00:00+00:00 2026-08-25T00:00:00+00:00 implFerris https://blog.implrust.com/posts/2026/08/microbit-sound-meter/ <video autoplay muted loop playsinline> <source src="/videos/2026/08/microbit-v2-embedded-rust-led-matrix-sound-meter.mp4" type="video/mp4"> </video> <p>My first dev board, the micro:bit, has been sitting in my box and staring at me every time I open my electronics box. So I thought it was time to give it a little attention and have some fun with it.</p> <p>In this project, I used the micro:bit’s built-in microphone to make its LED matrix react to sound. Try shouting at it and watch the LEDs light up!</p> <p>Your little one (or you) will love it ;)</p> <h2 id="project-setup"><a class="header-anchor no-hover-padding" href="#project-setup" aria-label="Anchor link for: project-setup"><span class="link-icon" aria-hidden="true"></span></a> Project Setup</h2> <p>I will be using <a rel="external" href="https://github.com/lulf/microbit-bsp"><code>microbit-bsp</code></a>, an async Board Support Package (BSP) for the BBC micro:bit V2.</p> <p>The <code>microbit-bsp</code> repository already has a nice <a rel="external" href="https://github.com/lulf/microbit-bsp/tree/main/examples/microphone">microphone example</a> that reads the sound level and lights up the LED matrix accordingly.</p> <p>I also implemented a similar project, <a rel="external" href="https://mb2.implrust.com/microphone/clap-to-smile.html">Clap to Smile</a>, in my <a rel="external" href="https://mb2.implrust.com/">Impl Rust for micro:bit</a> book. There, we detect a loud sound such as a clap and display a smiley on the LED matrix.</p> <p>So this time, instead of reacting to a single loud sound, we will keep track of the recent sound levels and turn them into a small moving wave on the LED matrix.</p> <p>I generated the project using the same template I use for the book:</p> <pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-entity z-name">cargo</span><span class="z-string"> generate</span><span class="z-constant"> --git</span><span class="z-string"> https://github.com/ImplFerris/mb2-template.git</span><span class="z-constant"> --rev</span><span class="z-string"> 3d07b56</span></span></code></pre> <p>When it asks, select Embassy and enabled the BSP.</p> <h2 id="reading-the-microphone"><a class="header-anchor no-hover-padding" href="#reading-the-microphone" aria-label="Anchor link for: reading-the-microphone"><span class="link-icon" aria-hidden="true"></span></a> Reading the Microphone</h2> <p>Let’s initialize the microphone using the SAADC peripheral.</p> <pre class="giallo z-code"><code data-lang="rust"><span class="giallo-l"><span class="z-storage z-type z-storage z-modifier">let mut</span><span class="z-variable z-other"> microphone</span><span class="z-keyword z-operator"> =</span><span class="z-entity z-name z-type"> Microphone</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">new</span><span class="z-punctuation">(</span><span class="z-variable z-other">board</span><span class="z-keyword z-operator">.</span><span>saadc</span><span class="z-punctuation">,</span><span class="z-variable z-other"> irqs</span><span class="z-punctuation">,</span><span class="z-variable z-other"> board</span><span class="z-keyword z-operator">.</span><span>microphone</span><span class="z-punctuation">,</span><span class="z-variable z-other"> board</span><span class="z-keyword z-operator">.</span><span>micen</span><span class="z-punctuation">);</span></span></code></pre><h2 id="collecting-sound-levels"><a class="header-anchor no-hover-padding" href="#collecting-sound-levels" aria-label="Anchor link for: collecting-sound-levels"><span class="link-icon" aria-hidden="true"></span></a> Collecting Sound Levels</h2> <p>Now let’s continuously read the sound level and keep track of the five most recent readings. We smooth the sound level by averaging the previous value with the new reading. This makes the LED display less jumpy.</p> <div class="admonition tip"> <div class="admonition-icon admonition-icon-tip"></div> <div class="admonition-content"> <strong class="admonition-title">TIP</strong> <p>There are many ways to process the sound level and display it on the LED matrix. The approach I used here is just one of them. Feel free to experiment and make your own version more fun and interesting, like the Clap to Smile project I mentioned earlier.</p> </div> </div> <pre class="giallo z-code"><code data-lang="rust"><span class="giallo-l"><span class="z-storage z-type z-storage z-modifier">let mut</span><span class="z-variable z-other"> smooth_level</span><span class="z-keyword z-operator"> =</span><span class="z-constant"> 0</span><span class="z-entity z-name z-type">usize</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-storage z-type z-storage z-modifier">let mut</span><span class="z-variable z-other"> levels</span><span class="z-keyword z-operator"> =</span><span class="z-punctuation"> [</span><span class="z-constant">0</span><span class="z-entity z-name z-type">usize</span><span class="z-punctuation">;</span><span class="z-constant"> 5</span><span class="z-punctuation">];</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-keyword z-control">loop</span><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-storage z-type"> let</span><span class="z-variable z-other"> sound_level</span><span class="z-keyword z-operator"> =</span><span class="z-variable z-other"> microphone</span><span class="z-keyword z-operator">.</span><span class="z-entity z-name z-function">sound_level</span><span class="z-punctuation">()</span><span class="z-keyword z-operator">.</span><span class="z-keyword z-control z-keyword">await as</span><span class="z-entity z-name z-type"> usize</span><span class="z-punctuation">;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-variable z-other"> smooth_level</span><span class="z-keyword z-operator"> =</span><span class="z-punctuation"> (</span><span class="z-variable z-other">smooth_level</span><span class="z-keyword z-operator"> +</span><span class="z-variable z-other"> sound_level</span><span class="z-punctuation">)</span><span class="z-keyword z-operator"> /</span><span class="z-constant"> 2</span><span class="z-punctuation">;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-variable z-other"> levels</span><span class="z-keyword z-operator">.</span><span class="z-entity z-name z-function">copy_within</span><span class="z-punctuation">(</span><span class="z-constant">1</span><span class="z-keyword z-operator">..</span><span class="z-constant">5</span><span class="z-punctuation">,</span><span class="z-constant"> 0</span><span class="z-punctuation">);</span></span> <span class="giallo-l"><span class="z-variable z-other"> levels</span><span class="z-punctuation">[</span><span class="z-constant">4</span><span class="z-punctuation">]</span><span class="z-keyword z-operator"> =</span><span class="z-variable z-other"> smooth_level</span><span class="z-punctuation">;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-entity z-name z-function"> display_sound_wave</span><span class="z-punctuation">(</span><span class="z-keyword z-operator">&amp;</span><span class="z-storage z-modifier">mut</span><span class="z-variable z-other"> display</span><span class="z-punctuation">,</span><span class="z-constant"> DISPLAY_DURATION</span><span class="z-punctuation">,</span><span class="z-keyword z-operator"> &amp;</span><span class="z-variable z-other">levels</span><span class="z-punctuation">)</span><span class="z-keyword z-operator">.</span><span class="z-keyword z-control">await</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span></code></pre> <p>We use <code>copy_within</code> to move the previous readings one position to the left and add the latest reading at the end. This makes the sound wave appear to move from right to left.</p> <h2 id="displaying-the-sound-wave"><a class="header-anchor no-hover-padding" href="#displaying-the-sound-wave" aria-label="Anchor link for: displaying-the-sound-wave"><span class="link-icon" aria-hidden="true"></span></a> Displaying the Sound Wave</h2> <p>Now let’s display the sound levels on the LED matrix.</p> <p>We use one column for each sound level. We convert each sound level into a value from 0 to 5, which tells us how many LEDs to light up in that column.</p> <p>The LEDs are lit from the bottom row upwards. So a low sound level produces a short column, while a loud sound produces a taller one.</p> <pre class="giallo z-code"><code data-lang="rust"><span class="giallo-l"><span class="z-keyword">async fn</span><span class="z-entity z-name z-function"> display_sound_wave</span><span class="z-punctuation">(</span><span class="z-variable z-other">display</span><span class="z-keyword z-operator">: &amp;</span><span class="z-storage z-modifier">mut</span><span class="z-entity z-name z-type"> LedMatrix</span><span class="z-punctuation">,</span><span class="z-variable z-other"> length</span><span class="z-keyword z-operator">:</span><span class="z-entity z-name z-type"> Duration</span><span class="z-punctuation">,</span><span class="z-variable z-other"> levels</span><span class="z-keyword z-operator">: &amp;</span><span class="z-punctuation">[</span><span class="z-entity z-name z-type">usize</span><span class="z-punctuation">;</span><span class="z-constant"> 5</span><span class="z-punctuation">]) {</span></span> <span class="giallo-l"><span class="z-storage z-type z-storage z-modifier"> let mut</span><span class="z-variable z-other"> frame</span><span class="z-keyword z-operator"> =</span><span class="z-entity z-name z-type"> Frame</span><span class="z-keyword z-operator">::</span><span class="z-punctuation">&lt;</span><span class="z-constant">5</span><span class="z-punctuation">,</span><span class="z-constant"> 5</span><span class="z-punctuation">&gt;</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">empty</span><span class="z-punctuation">();</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-storage z-type"> const</span><span class="z-constant"> MAX_ROWS</span><span class="z-keyword z-operator">:</span><span class="z-entity z-name z-type"> usize</span><span class="z-keyword z-operator"> =</span><span class="z-constant"> 5</span><span class="z-punctuation">;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-keyword z-control"> for</span><span class="z-punctuation"> (</span><span class="z-variable z-other">column</span><span class="z-punctuation">,</span><span class="z-variable z-other"> level</span><span class="z-punctuation">)</span><span class="z-keyword"> in</span><span class="z-variable z-other"> levels</span><span class="z-keyword z-operator">.</span><span class="z-entity z-name z-function">iter</span><span class="z-punctuation">()</span><span class="z-keyword z-operator">.</span><span class="z-entity z-name z-function">enumerate</span><span class="z-punctuation">()</span><span class="z-keyword z-operator">.</span><span class="z-entity z-name z-function">take</span><span class="z-punctuation">(</span><span class="z-constant">5</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-storage z-type"> let</span><span class="z-variable z-other"> height</span><span class="z-keyword z-operator"> =</span><span class="z-keyword z-control"> match</span><span class="z-variable z-other"> level</span><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-constant"> 0</span><span class="z-keyword z-operator">..=</span><span class="z-constant">10</span><span class="z-keyword z-operator"> =&gt;</span><span class="z-constant"> 0</span><span class="z-punctuation">,</span></span> <span class="giallo-l"><span class="z-constant"> 11</span><span class="z-keyword z-operator">..=</span><span class="z-constant">24</span><span class="z-keyword z-operator"> =&gt;</span><span class="z-constant"> 1</span><span class="z-punctuation">,</span></span> <span class="giallo-l"><span class="z-constant"> 25</span><span class="z-keyword z-operator">..=</span><span class="z-constant">38</span><span class="z-keyword z-operator"> =&gt;</span><span class="z-constant"> 2</span><span class="z-punctuation">,</span></span> <span class="giallo-l"><span class="z-constant"> 39</span><span class="z-keyword z-operator">..=</span><span class="z-constant">52</span><span class="z-keyword z-operator"> =&gt;</span><span class="z-constant"> 3</span><span class="z-punctuation">,</span></span> <span class="giallo-l"><span class="z-constant"> 53</span><span class="z-keyword z-operator">..=</span><span class="z-constant">66</span><span class="z-keyword z-operator"> =&gt;</span><span class="z-constant"> 4</span><span class="z-punctuation">,</span></span> <span class="giallo-l"><span class="z-variable z-other"> _</span><span class="z-keyword z-operator"> =&gt;</span><span class="z-constant"> 5</span><span class="z-punctuation">,</span></span> <span class="giallo-l"><span class="z-punctuation"> };</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-keyword z-control"> for</span><span class="z-variable z-other"> row</span><span class="z-keyword"> in</span><span class="z-punctuation"> (</span><span class="z-constant">MAX_ROWS</span><span class="z-keyword z-operator"> -</span><span class="z-variable z-other"> height</span><span class="z-punctuation">)</span><span class="z-keyword z-operator">..</span><span class="z-constant">MAX_ROWS</span><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-variable z-other"> frame</span><span class="z-keyword z-operator">.</span><span class="z-entity z-name z-function">set</span><span class="z-punctuation">(</span><span class="z-variable z-other">column</span><span class="z-punctuation">,</span><span class="z-variable z-other"> row</span><span class="z-punctuation">);</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-variable z-other"> display</span><span class="z-keyword z-operator">.</span><span class="z-entity z-name z-function">display</span><span class="z-punctuation">(</span><span class="z-variable z-other">frame</span><span class="z-punctuation">,</span><span class="z-variable z-other"> length</span><span class="z-punctuation">)</span><span class="z-keyword z-operator">.</span><span class="z-keyword z-control">await</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span></code></pre><h2 id="completed-project"><a class="header-anchor no-hover-padding" href="#completed-project" aria-label="Anchor link for: completed-project"><span class="link-icon" aria-hidden="true"></span></a> Completed Project</h2> <p>You can check out the <a rel="external" href="https://github.com/ImplFerris/microbit-sound-meter">completed project</a> if you want to clone it and build on top of it.</p> <h2 id="run-the-program"><a class="header-anchor no-hover-padding" href="#run-the-program" aria-label="Anchor link for: run-the-program"><span class="link-icon" aria-hidden="true"></span></a> Run the Program</h2> <p>Flash the program to the micro:bit and make some noise. As you speak or shout near the microphone, the LED matrix reacts to the sound and the wave moves across the display.</p> <pre class="giallo z-code"><code data-lang="shellscript"><span class="giallo-l"><span class="z-entity z-name">cargo</span><span class="z-string"> run</span></span></code></pre><h2 id="full-code"><a class="header-anchor no-hover-padding" href="#full-code" aria-label="Anchor link for: full-code"><span class="link-icon" aria-hidden="true"></span></a> Full Code</h2> <pre class="giallo z-code"><code data-lang="rust"><span class="giallo-l"><span class="z-punctuation">#</span><span>!</span><span class="z-punctuation">[</span><span>no_std</span><span class="z-punctuation">]</span></span> <span class="giallo-l"><span class="z-punctuation">#</span><span>!</span><span class="z-punctuation">[</span><span>no_main</span><span class="z-punctuation">]</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-keyword">use</span><span class="z-entity z-name"> defmt</span><span class="z-keyword z-operator">::</span><span>info</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-keyword">use</span><span class="z-entity z-name"> embassy_executor</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-type">Spawner</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-keyword">use</span><span class="z-entity z-name"> embassy_time</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-type">Duration</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-keyword">use</span><span class="z-entity z-name"> microbit_bsp</span><span class="z-keyword z-operator">::</span><span class="z-punctuation">{</span></span> <span class="giallo-l"><span class="z-entity z-name z-type"> LedMatrix</span><span class="z-punctuation">,</span><span class="z-entity z-name z-type"> Microbit</span><span class="z-punctuation">,</span></span> <span class="giallo-l"><span class="z-entity z-name"> display</span><span class="z-keyword z-operator">::</span><span class="z-punctuation">{</span><span class="z-entity z-name z-type">Brightness</span><span class="z-punctuation">,</span><span class="z-entity z-name z-type"> Frame</span><span class="z-punctuation">},</span></span> <span class="giallo-l"><span class="z-entity z-name"> embassy_nrf</span><span class="z-keyword z-operator">::</span><span class="z-punctuation">{</span><span>bind_interrupts</span><span class="z-punctuation">,</span><span class="z-entity z-name"> saadc</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-type">InterruptHandler</span><span class="z-punctuation">},</span></span> <span class="giallo-l"><span class="z-entity z-name"> mic</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-type">Microphone</span><span class="z-punctuation">,</span></span> <span class="giallo-l"><span class="z-punctuation">};</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-keyword">use</span><span class="z-punctuation"> {</span><span>defmt_rtt </span><span class="z-keyword">as</span><span> _</span><span class="z-punctuation">,</span><span> panic_probe </span><span class="z-keyword">as</span><span> _</span><span class="z-punctuation">};</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-storage z-type">const</span><span class="z-constant"> DISPLAY_DURATION</span><span class="z-keyword z-operator">:</span><span class="z-entity z-name z-type"> Duration</span><span class="z-keyword z-operator"> =</span><span class="z-entity z-name z-type"> Duration</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">from_millis</span><span class="z-punctuation">(</span><span class="z-constant">50</span><span class="z-punctuation">);</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-entity z-name z-function">bind_interrupts!</span><span class="z-punctuation">(</span></span> <span class="giallo-l"><span class="z-storage z-type"> struct</span><span class="z-entity z-name z-type"> InterruptRequests</span><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-constant"> SAADC</span><span class="z-keyword z-operator"> =&gt;</span><span class="z-entity z-name z-type"> InterruptHandler</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation">);</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-punctuation">#[</span><span>embassy_executor</span><span class="z-keyword z-operator">::</span><span>main</span><span class="z-punctuation">]</span></span> <span class="giallo-l"><span class="z-keyword">async fn</span><span class="z-entity z-name z-function"> main</span><span class="z-punctuation">(</span><span class="z-variable z-other">_spawner</span><span class="z-keyword z-operator">:</span><span class="z-entity z-name z-type"> Spawner</span><span class="z-punctuation">)</span><span class="z-keyword z-operator"> -&gt;</span><span class="z-keyword z-operator z-logical"> !</span><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-storage z-type"> let</span><span class="z-variable z-other"> board</span><span class="z-keyword z-operator"> =</span><span class="z-entity z-name z-type"> Microbit</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">default</span><span class="z-punctuation">();</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-storage z-type z-storage z-modifier"> let mut</span><span class="z-variable z-other"> display</span><span class="z-keyword z-operator"> =</span><span class="z-variable z-other"> board</span><span class="z-keyword z-operator">.</span><span>display</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-variable z-other"> display</span><span class="z-keyword z-operator">.</span><span class="z-entity z-name z-function">set_brightness</span><span class="z-punctuation">(</span><span class="z-entity z-name">Brightness</span><span class="z-keyword z-operator">::</span><span class="z-constant">MAX</span><span class="z-punctuation">);</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-storage z-type"> let</span><span class="z-variable z-other"> irqs</span><span class="z-keyword z-operator"> =</span><span class="z-entity z-name z-type"> InterruptRequests</span><span class="z-punctuation"> {};</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-storage z-type z-storage z-modifier"> let mut</span><span class="z-variable z-other"> microphone</span><span class="z-keyword z-operator"> =</span><span class="z-entity z-name z-type"> Microphone</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">new</span><span class="z-punctuation">(</span><span class="z-variable z-other">board</span><span class="z-keyword z-operator">.</span><span>saadc</span><span class="z-punctuation">,</span><span class="z-variable z-other"> irqs</span><span class="z-punctuation">,</span><span class="z-variable z-other"> board</span><span class="z-keyword z-operator">.</span><span>microphone</span><span class="z-punctuation">,</span><span class="z-variable z-other"> board</span><span class="z-keyword z-operator">.</span><span>micen</span><span class="z-punctuation">);</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-storage z-type z-storage z-modifier"> let mut</span><span class="z-variable z-other"> smooth_level</span><span class="z-keyword z-operator"> =</span><span class="z-constant"> 0</span><span class="z-entity z-name z-type">usize</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-storage z-type z-storage z-modifier"> let mut</span><span class="z-variable z-other"> levels</span><span class="z-keyword z-operator"> =</span><span class="z-punctuation"> [</span><span class="z-constant">0</span><span class="z-entity z-name z-type">usize</span><span class="z-punctuation">;</span><span class="z-constant"> 5</span><span class="z-punctuation">];</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-keyword z-control"> loop</span><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-storage z-type"> let</span><span class="z-variable z-other"> sound_level</span><span class="z-keyword z-operator"> =</span><span class="z-variable z-other"> microphone</span><span class="z-keyword z-operator">.</span><span class="z-entity z-name z-function">sound_level</span><span class="z-punctuation">()</span><span class="z-keyword z-operator">.</span><span class="z-keyword z-control z-keyword">await as</span><span class="z-entity z-name z-type"> usize</span><span class="z-punctuation">;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-variable z-other"> smooth_level</span><span class="z-keyword z-operator"> =</span><span class="z-punctuation"> (</span><span class="z-variable z-other">smooth_level</span><span class="z-keyword z-operator"> +</span><span class="z-variable z-other"> sound_level</span><span class="z-punctuation">)</span><span class="z-keyword z-operator"> /</span><span class="z-constant"> 2</span><span class="z-punctuation">;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-entity z-name z-function"> info!</span><span class="z-punctuation">(&quot;</span><span class="z-string">Sound level: </span><span class="z-punctuation">{}&quot;,</span><span class="z-variable z-other"> smooth_level</span><span class="z-punctuation">);</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-variable z-other"> levels</span><span class="z-keyword z-operator">.</span><span class="z-entity z-name z-function">copy_within</span><span class="z-punctuation">(</span><span class="z-constant">1</span><span class="z-keyword z-operator">..</span><span class="z-constant">5</span><span class="z-punctuation">,</span><span class="z-constant"> 0</span><span class="z-punctuation">);</span></span> <span class="giallo-l"><span class="z-variable z-other"> levels</span><span class="z-punctuation">[</span><span class="z-constant">4</span><span class="z-punctuation">]</span><span class="z-keyword z-operator"> =</span><span class="z-variable z-other"> smooth_level</span><span class="z-punctuation">;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-entity z-name z-function"> display_sound_wave</span><span class="z-punctuation">(</span><span class="z-keyword z-operator">&amp;</span><span class="z-storage z-modifier">mut</span><span class="z-variable z-other"> display</span><span class="z-punctuation">,</span><span class="z-constant"> DISPLAY_DURATION</span><span class="z-punctuation">,</span><span class="z-keyword z-operator"> &amp;</span><span class="z-variable z-other">levels</span><span class="z-punctuation">)</span><span class="z-keyword z-operator">.</span><span class="z-keyword z-control">await</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-keyword">async fn</span><span class="z-entity z-name z-function"> display_sound_wave</span><span class="z-punctuation">(</span><span class="z-variable z-other">display</span><span class="z-keyword z-operator">: &amp;</span><span class="z-storage z-modifier">mut</span><span class="z-entity z-name z-type"> LedMatrix</span><span class="z-punctuation">,</span><span class="z-variable z-other"> length</span><span class="z-keyword z-operator">:</span><span class="z-entity z-name z-type"> Duration</span><span class="z-punctuation">,</span><span class="z-variable z-other"> levels</span><span class="z-keyword z-operator">: &amp;</span><span class="z-punctuation">[</span><span class="z-entity z-name z-type">usize</span><span class="z-punctuation">;</span><span class="z-constant"> 5</span><span class="z-punctuation">]) {</span></span> <span class="giallo-l"><span class="z-storage z-type z-storage z-modifier"> let mut</span><span class="z-variable z-other"> frame</span><span class="z-keyword z-operator"> =</span><span class="z-entity z-name z-type"> Frame</span><span class="z-keyword z-operator">::</span><span class="z-punctuation">&lt;</span><span class="z-constant">5</span><span class="z-punctuation">,</span><span class="z-constant"> 5</span><span class="z-punctuation">&gt;</span><span class="z-keyword z-operator">::</span><span class="z-entity z-name z-function">empty</span><span class="z-punctuation">();</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-storage z-type"> const</span><span class="z-constant"> MAX_ROWS</span><span class="z-keyword z-operator">:</span><span class="z-entity z-name z-type"> usize</span><span class="z-keyword z-operator"> =</span><span class="z-constant"> 5</span><span class="z-punctuation">;</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-keyword z-control"> for</span><span class="z-punctuation"> (</span><span class="z-variable z-other">column</span><span class="z-punctuation">,</span><span class="z-variable z-other"> level</span><span class="z-punctuation">)</span><span class="z-keyword"> in</span><span class="z-variable z-other"> levels</span><span class="z-keyword z-operator">.</span><span class="z-entity z-name z-function">iter</span><span class="z-punctuation">()</span><span class="z-keyword z-operator">.</span><span class="z-entity z-name z-function">enumerate</span><span class="z-punctuation">()</span><span class="z-keyword z-operator">.</span><span class="z-entity z-name z-function">take</span><span class="z-punctuation">(</span><span class="z-constant">5</span><span class="z-punctuation">) {</span></span> <span class="giallo-l"><span class="z-storage z-type"> let</span><span class="z-variable z-other"> height</span><span class="z-keyword z-operator"> =</span><span class="z-keyword z-control"> match</span><span class="z-variable z-other"> level</span><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-constant"> 0</span><span class="z-keyword z-operator">..=</span><span class="z-constant">10</span><span class="z-keyword z-operator"> =&gt;</span><span class="z-constant"> 0</span><span class="z-punctuation">,</span></span> <span class="giallo-l"><span class="z-constant"> 11</span><span class="z-keyword z-operator">..=</span><span class="z-constant">24</span><span class="z-keyword z-operator"> =&gt;</span><span class="z-constant"> 1</span><span class="z-punctuation">,</span></span> <span class="giallo-l"><span class="z-constant"> 25</span><span class="z-keyword z-operator">..=</span><span class="z-constant">38</span><span class="z-keyword z-operator"> =&gt;</span><span class="z-constant"> 2</span><span class="z-punctuation">,</span></span> <span class="giallo-l"><span class="z-constant"> 39</span><span class="z-keyword z-operator">..=</span><span class="z-constant">52</span><span class="z-keyword z-operator"> =&gt;</span><span class="z-constant"> 3</span><span class="z-punctuation">,</span></span> <span class="giallo-l"><span class="z-constant"> 53</span><span class="z-keyword z-operator">..=</span><span class="z-constant">66</span><span class="z-keyword z-operator"> =&gt;</span><span class="z-constant"> 4</span><span class="z-punctuation">,</span></span> <span class="giallo-l"><span class="z-variable z-other"> _</span><span class="z-keyword z-operator"> =&gt;</span><span class="z-constant"> 5</span><span class="z-punctuation">,</span></span> <span class="giallo-l"><span class="z-punctuation"> };</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-keyword z-control"> for</span><span class="z-variable z-other"> row</span><span class="z-keyword"> in</span><span class="z-punctuation"> (</span><span class="z-constant">MAX_ROWS</span><span class="z-keyword z-operator"> -</span><span class="z-variable z-other"> height</span><span class="z-punctuation">)</span><span class="z-keyword z-operator">..</span><span class="z-constant">MAX_ROWS</span><span class="z-punctuation"> {</span></span> <span class="giallo-l"><span class="z-variable z-other"> frame</span><span class="z-keyword z-operator">.</span><span class="z-entity z-name z-function">set</span><span class="z-punctuation">(</span><span class="z-variable z-other">column</span><span class="z-punctuation">,</span><span class="z-variable z-other"> row</span><span class="z-punctuation">);</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"><span class="z-punctuation"> }</span></span> <span class="giallo-l"></span> <span class="giallo-l"><span class="z-variable z-other"> display</span><span class="z-keyword z-operator">.</span><span class="z-entity z-name z-function">display</span><span class="z-punctuation">(</span><span class="z-variable z-other">frame</span><span class="z-punctuation">,</span><span class="z-variable z-other"> length</span><span class="z-punctuation">)</span><span class="z-keyword z-operator">.</span><span class="z-keyword z-control">await</span><span class="z-punctuation">;</span></span> <span class="giallo-l"><span class="z-punctuation">}</span></span></code></pre> Embedded Rust code using Embassy and microbit-bsp to read the micro:bit V2's built-in microphone and make its onboard LED matrix react to sound.