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<!DOCTYPE html><html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><meta name="generator" content="rustdoc"><meta name="description" content="Read the value from a RORegister, RWRegister, UnsafeRORegister, or UnsafeRWRegister."><title>read_reg in imxrt_ral - Rust</title><script>if(window.location.protocol!=="file:")document.head.insertAdjacentHTML("beforeend","SourceSerif4-Regular-46f98efaafac5295.ttf.woff2,FiraSans-Regular-018c141bf0843ffd.woff2,FiraSans-Medium-8f9a781e4970d388.woff2,SourceCodePro-Regular-562dcc5011b6de7d.ttf.woff2,SourceCodePro-Semibold-d899c5a5c4aeb14a.ttf.woff2".split(",").map(f=>`<link rel="preload" as="font" type="font/woff2" crossorigin href="../static.files/${f}">`).join(""))</script><link rel="stylesheet" href="../static.files/normalize-76eba96aa4d2e634.css"><link rel="stylesheet" href="../static.files/rustdoc-492a78a4a87dcc01.css"><meta name="rustdoc-vars" data-root-path="../" data-static-root-path="../static.files/" data-current-crate="imxrt_ral" data-themes="" data-resource-suffix="" data-rustdoc-version="1.82.0 (f6e511eec 2024-10-15)" data-channel="1.82.0" data-search-js="search-a99f1315e7cc5121.js" data-settings-js="settings-4313503d2e1961c2.js" ><script src="../static.files/storage-118b08c4c78b968e.js"></script><script defer src="sidebar-items.js"></script><script defer src="../static.files/main-921df33f47b8780c.js"></script><noscript><link rel="stylesheet" href="../static.files/noscript-3b12f09e550e0385.css"></noscript><link rel="alternate icon" type="image/png" href="../static.files/favicon-32x32-422f7d1d52889060.png"><link rel="icon" type="image/svg+xml" href="../static.files/favicon-2c020d218678b618.svg"></head><body class="rustdoc macro"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="mobile-topbar"><button class="sidebar-menu-toggle" title="show sidebar"></button></nav><nav class="sidebar"><div class="sidebar-crate"><h2><a href="../imxrt_ral/index.html">imxrt_<wbr>ral</a><span class="version">0.5.3</span></h2></div><div class="sidebar-elems"></div></nav><div class="sidebar-resizer"></div><main><div class="width-limiter"><rustdoc-search></rustdoc-search><section id="main-content" class="content"><div class="main-heading"><h1>Macro <a href="index.html">imxrt_ral</a>::<wbr><a class="macro" href="#">read_reg</a><button id="copy-path" title="Copy item path to clipboard">Copy item path</button></h1><span class="out-of-band"><a class="src" href="../src/ral_registers/lib.rs.html#544">source</a> · <button id="toggle-all-docs" title="collapse all docs">[<span>−</span>]</button></span></div><pre class="rust item-decl"><span class="macro">macro_rules!</span> read_reg {
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( <span class="macro-nonterminal">$periph</span>:path, <span class="macro-nonterminal">$instance</span>:expr, <span class="macro-nonterminal">$reg</span>:ident $([<span class="macro-nonterminal">$offset</span>:expr])<span class="kw-2">*</span>, $( <span class="macro-nonterminal">$field</span>:ident ),+ $(,)<span class="question-mark">? </span>) => { ... };
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( <span class="macro-nonterminal">$periph</span>:path, <span class="macro-nonterminal">$instance</span>:expr, <span class="macro-nonterminal">$reg</span>:ident $([<span class="macro-nonterminal">$offset</span>:expr])<span class="kw-2">*</span>, <span class="macro-nonterminal">$field</span>:ident $(<span class="macro-nonterminal">$cmp</span>:tt)* ) => { ... };
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( <span class="macro-nonterminal">$periph</span>:path, <span class="macro-nonterminal">$instance</span>:expr, <span class="macro-nonterminal">$reg</span>:ident $([<span class="macro-nonterminal">$offset</span>:expr])* ) => { ... };
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}</pre><details class="toggle top-doc" open><summary class="hideme"><span>Expand description</span></summary><div class="docblock"><p>Read the value from a RORegister, RWRegister, UnsafeRORegister, or UnsafeRWRegister.</p>
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<h2 id="examples"><a class="doc-anchor" href="#examples">§</a>Examples</h2>
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<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="comment">// Safely acquire the peripheral instance (will panic if already acquired)
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</span><span class="kw">let </span>gpioa = stm32ral::gpio::GPIOA::take().unwrap();
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<span class="comment">// Read the whole register.
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</span><span class="kw">let </span>val = <span class="macro">read_reg!</span>(stm32ral::gpio, gpioa, IDR);
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<span class="comment">// Read one field from the register.
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</span><span class="kw">let </span>val = <span class="macro">read_reg!</span>(stm32ral::gpio, gpioa, IDR, IDR2);
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<span class="comment">// Read multiple fields from the register.
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</span><span class="kw">let </span>(val1, val2, val3) = <span class="macro">read_reg!</span>(stm32ral::gpio, gpioa, IDR, IDR0, IDR1, IDR2);
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<span class="comment">// Check if one field is equal to a specific value, with the field's named values in scope.
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</span><span class="kw">while </span><span class="macro">read_reg!</span>(stm32ral::gpio, gpioa, IDR, IDR2 == High) {}
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<span class="comment">// Unsafe access without requiring you to first `take()` the instance
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</span><span class="kw">let </span>val = <span class="kw">unsafe </span>{ <span class="macro">read_reg!</span>(stm32ral::gpio, GPIOA, IDR) };</code></pre></div>
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<p>To support register arrays, each macro form also supports one or more array indices after the
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register. For example, <code>read_reg!(stm32ral::gpio, gpioa, ODR[2]);</code> reads from the third
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register of an <code>ODR</code> register array.</p>
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<h2 id="usage"><a class="doc-anchor" href="#usage">§</a>Usage</h2>
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<p>Like <code>write_reg!</code>, this macro can be used multiple ways, either reading the entire register or
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reading a one or more fields from it and potentially performing a comparison with one field.</p>
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<p>In all cases, the first arguments are:</p>
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<ul>
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<li>the path to the peripheral module: <code>stm32ral::gpio</code>,</li>
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<li>a reference to the instance of that peripheral: ‘gpioa’ (anything which dereferences to
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<code>RegisterBlock</code>, such as <code>Instance</code>, <code>&Instance</code>, <code>&RegisterBlock</code>, or
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<code>*const RegisterBlock</code>),</li>
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<li>the register (and offset, for arrays) you wish to access: <code>IDR</code> (a field on the
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<code>RegisterBlock</code>).</li>
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</ul>
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<p>In the whole-register usage, the macro simply returns the register’s value:</p>
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<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="comment">// Read the entire value of GPIOA.IDR into `val`.
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</span><span class="kw">let </span>val = <span class="macro">read_reg!</span>(stm32ral::gpio, gpioa, IDR);</code></pre></div>
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<p>For reading individual fields, the macro masks and shifts appropriately:</p>
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<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="comment">// Read just the value of the field GPIOA.IDR2 into `val`.
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</span><span class="kw">let </span>val = <span class="macro">read_reg!</span>(stm32ral::gpio, gpioa, IDR, IDR2);
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<span class="comment">// As above, but expanded for exposition:
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</span><span class="kw">let </span>val = ((<span class="kw-2">*</span>gpioa).IDR.read() & stm32ral::gpio::IDR::IDR2::mask)
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>> stm32ral::gpio::IDR::IDR2::offset;
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<span class="comment">// Read multiple fields
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</span><span class="kw">let </span>(val1, val2) = <span class="macro">read_reg!</span>(stm32ral::gpio, gpioa, IDR, IDR2, IDR3);
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<span class="comment">// As above, but expanded for exposition:
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</span><span class="kw">let </span>(val1, val2) = { <span class="kw">let </span>val = (<span class="kw-2">*</span>gpioa).IDR.read();
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((val & stm32ral::gpio::IDR::IDR2::mask) >> stm32ral::gpio::IDR::IDR2::offset,
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(val & stm32ral::gpio::IDR::IDR3::mask) >> stm32ral::gpio::IDR::IDR3::offset,
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)};</code></pre></div>
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<p>For comparing a single field, the macro masks and shifts and then performs the comparison:</p>
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<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="comment">// Loop while PA2 is High.
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</span><span class="kw">while </span><span class="macro">read_reg!</span>(stm32ral::gpio, gpioa, IDR, IDR2 == High) {}
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<span class="comment">// Only proceed if the clock is not the HSI.
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</span><span class="kw">if </span><span class="macro">read_reg!</span>(stm32ral::rcc, rcc, CFGR, SWS != HSI) { }
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<span class="comment">// Equivalent expansion:
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</span><span class="kw">if </span>(((<span class="kw-2">*</span>rcc).CFGR.read() & stm32ral::rcc::CFGR::SWS::mask)
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>> stm32ral::rcc::CFGR::SWS::offset) != stm32ral::rcc::CFGR::SWS::R::HSI { }</code></pre></div>
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<h2 id="safety"><a class="doc-anchor" href="#safety">§</a>Safety</h2>
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<p>This macro will require an unsafe function or block when used with an UnsafeRWRegister or
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UnsafeRORegister, but not if used with RWRegister, or RORegister.</p>
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<p>When run in an unsafe context, peripheral instances are directly accessible without requiring
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having called <code>take()</code> beforehand:</p>
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<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">let </span>val = <span class="kw">unsafe </span>{ <span class="macro">read_reg!</span>(stm32ral::gpio, GPIOA, MODER) };</code></pre></div>
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<p>This works because <code>GPIOA</code> is a <code>*const RegisterBlock</code> in the <code>stm32ral::gpio</code> module;
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and the macro brings such constants into scope and then dereferences the provided reference.</p>
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</div></details></section></div></main></body></html>
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