add userguide for GPIO
related to https://github.com/google/periph/issues/432 fixes https://github.com/gokrazy/gokrazy/issues/33
This commit is contained in:
Michael Stapelberg
parent
59d57578b9
commit
1ec8cbf7d9
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<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9"
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xmlns:xhtml="http://www.w3.org/1999/xhtml">
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<url>
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<loc>https://gokrazy.org/userguide/gpio/</loc>
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</url>
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<url>
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<loc>https://gokrazy.org/userguide/remotesyslog/</loc>
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</url>
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122
docs/userguide/gpio/index.html
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docs/userguide/gpio/index.html
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<!DOCTYPE html>
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<html> <head>
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<meta charset="utf-8">
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<meta http-equiv="X-UA-Compatible" content="IE=edge">
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<meta name="viewport" content="width=device-width, initial-scale=1">
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<title>Controlling a GPIO input/output pin</title>
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<link rel="stylesheet" href="//maxcdn.bootstrapcdn.com/bootstrap/3.3.2/css/bootstrap.min.css">
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<link rel="stylesheet" href="//maxcdn.bootstrapcdn.com/font-awesome/4.3.0/css/font-awesome.min.css">
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<link href="/jumbotron-narrow.css" rel="stylesheet">
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<link rel="stylesheet" href="//fonts.googleapis.com/css?family=Open+Sans:300,300italic,400,400italic,600,600italic%7CNoto+Serif:400,400italic,700,700italic%7CDroid+Sans+Mono:400">
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<style type="text/css">
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body {
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font-family: "Open Sans";
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}
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.table-striped>tr:nth-child(odd){
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background-color:red;
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}
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</style>
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</head>
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<body>
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<div class="container"><div class="header"><nav>
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<ul class="nav nav-pills pull-right">
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<li role="presentation" class=""><a href="/">Home </a></li>
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<li role="presentation" class=""><a href="/platforms/">Platforms </a></li>
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<li role="presentation" class=""><a href="/quickstart/">Quickstart </a></li>
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<li role="presentation" class=""><a href="/showcase/">Showcase </a></li>
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<li role="presentation" class=""><a href="/userguide/">Userguide </a></li>
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<li role="presentation" class=""><a href="https://github.com/gokrazy/gokrazy">Source </a></li>
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</ul>
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</nav>
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<h3 class="text-muted">gokrazy</h3>
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</div>
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<h1 id="controlling-a-gpio-inputoutput-pin">Controlling a GPIO input/output pin</h1>
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<p>In this guide, we are using <a href="https://periph.io/">periph.io</a>, a library for
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peripheral I/O in Go, to set one of the Raspberry Pi’s General Purpose I/O
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(GPIO) pins to a logical high (3.3V) or low (0V) signal.</p>
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<p>periph.io supports the Raspberry Pi 3 and Raspberry Pi 4, starting with version
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<code>v3.6.4</code>.</p>
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<h2 id="connect-gpio-pins-based-on-pinout">Connect GPIO pins based on pinout</h2>
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<p><a href="https://pinout.xyz"><img src="/img/raspberry-pi-pinout.png" width="700" align="right" style="border: 1px solid grey; margin-bottom: 2em; margin-top: 1em"></a></p>
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<p>To verify the code is doing what we expect, let’s connect a multimeter as per
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<a href="https://pinout.xyz">pinout.xyz</a>’s pinout:</p>
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<ul>
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<li>pin number 18 (signal <code>BCM24</code>, labeled <code>24</code> in the pinout above)</li>
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<li>pin number 20 (signal <code>GND</code>)</li>
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</ul>
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<p>We need to set the multimeter to “Voltage measurement, DC (direct current)”.</p>
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<h2 id="setting-an-output-pin-signal">Setting an output pin signal</h2>
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<p>To set the pin high and low, alternatingly, with a 5 second frequency, we will
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be using the <code>hello-gpio</code> program, which is a slightly modified version of the
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example at <a href="https://periph.io/device/led/">periph.io/device/led</a>:</p>
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<div class="highlight"><pre style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4"><code class="language-go" data-lang="go"><span style="color:#f92672">package</span> <span style="color:#a6e22e">main</span>
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<span style="color:#f92672">import</span> (
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<span style="color:#e6db74">"log"</span>
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<span style="color:#e6db74">"time"</span>
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<span style="color:#e6db74">"periph.io/x/periph/conn/gpio"</span>
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<span style="color:#e6db74">"periph.io/x/periph/host"</span>
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<span style="color:#e6db74">"periph.io/x/periph/host/rpi"</span>
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)
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<span style="color:#66d9ef">func</span> <span style="color:#a6e22e">doGPIO</span>() <span style="color:#66d9ef">error</span> {
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<span style="color:#a6e22e">log</span>.<span style="color:#a6e22e">Printf</span>(<span style="color:#e6db74">"Loading periph.io drivers"</span>)
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<span style="color:#75715e">// Load periph.io drivers:
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</span><span style="color:#75715e"></span> <span style="color:#66d9ef">if</span> <span style="color:#a6e22e">_</span>, <span style="color:#a6e22e">err</span> <span style="color:#f92672">:=</span> <span style="color:#a6e22e">host</span>.<span style="color:#a6e22e">Init</span>(); <span style="color:#a6e22e">err</span> <span style="color:#f92672">!=</span> <span style="color:#66d9ef">nil</span> {
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<span style="color:#66d9ef">return</span> <span style="color:#a6e22e">err</span>
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}
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<span style="color:#a6e22e">log</span>.<span style="color:#a6e22e">Printf</span>(<span style="color:#e6db74">"Toggling GPIO forever"</span>)
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<span style="color:#a6e22e">t</span> <span style="color:#f92672">:=</span> <span style="color:#a6e22e">time</span>.<span style="color:#a6e22e">NewTicker</span>(<span style="color:#ae81ff">5</span> <span style="color:#f92672">*</span> <span style="color:#a6e22e">time</span>.<span style="color:#a6e22e">Second</span>)
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<span style="color:#66d9ef">for</span> <span style="color:#a6e22e">l</span> <span style="color:#f92672">:=</span> <span style="color:#a6e22e">gpio</span>.<span style="color:#a6e22e">Low</span>; ; <span style="color:#a6e22e">l</span> = !<span style="color:#a6e22e">l</span> {
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<span style="color:#a6e22e">log</span>.<span style="color:#a6e22e">Printf</span>(<span style="color:#e6db74">"setting GPIO pin number 18 (signal BCM24) to %v"</span>, <span style="color:#a6e22e">l</span>)
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<span style="color:#75715e">// Lookup a pin by its location on the board:
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</span><span style="color:#75715e"></span> <span style="color:#66d9ef">if</span> <span style="color:#a6e22e">err</span> <span style="color:#f92672">:=</span> <span style="color:#a6e22e">rpi</span>.<span style="color:#a6e22e">P1_18</span>.<span style="color:#a6e22e">Out</span>(<span style="color:#a6e22e">l</span>); <span style="color:#a6e22e">err</span> <span style="color:#f92672">!=</span> <span style="color:#66d9ef">nil</span> {
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<span style="color:#66d9ef">return</span> <span style="color:#a6e22e">err</span>
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}
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<span style="color:#f92672"><-</span><span style="color:#a6e22e">t</span>.<span style="color:#a6e22e">C</span>
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}
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<span style="color:#66d9ef">return</span> <span style="color:#66d9ef">nil</span>
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}
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<span style="color:#66d9ef">func</span> <span style="color:#a6e22e">main</span>() {
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<span style="color:#66d9ef">if</span> <span style="color:#a6e22e">err</span> <span style="color:#f92672">:=</span> <span style="color:#a6e22e">doGPIO</span>(); <span style="color:#a6e22e">err</span> <span style="color:#f92672">!=</span> <span style="color:#66d9ef">nil</span> {
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<span style="color:#a6e22e">log</span>.<span style="color:#a6e22e">Fatal</span>(<span style="color:#a6e22e">err</span>)
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}
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}
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</code></pre></div><p>Install the program on your Raspberry Pi using gokrazy (see <a href="/quickstart/">Quickstart</a>):</p>
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<div class="highlight"><pre style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4"><code class="language-shell" data-lang="shell">gokr-packer <span style="color:#ae81ff">\
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</span><span style="color:#ae81ff"></span> -update<span style="color:#f92672">=</span>yes <span style="color:#ae81ff">\
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</span><span style="color:#ae81ff"></span> github.com/gokrazy/hello <span style="color:#ae81ff">\
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</span><span style="color:#ae81ff"></span> github.com/gokrazy/breakglass <span style="color:#ae81ff">\
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</span><span style="color:#ae81ff"></span> github.com/gokrazy/serial-busybox <span style="color:#ae81ff">\
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</span><span style="color:#ae81ff"></span> github.com/gokrazy/hello-gpio
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</code></pre></div><p>…and wait a few seconds for it to reboot.</p>
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<p>At this point, we should be able to see the high/low signal on the multimeter,
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alternating between 3.3V (high) and 0V (low) every 5 seconds:</p>
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<p><a href="/img/2020-06-15-gpio.jpg"><img src="/img/2020-06-15-gpio.thumb.jpg" srcset="/img/2020-06-15-gpio.thumb.2x.jpg 2x,/img/2020-06-15-gpio.thumb.3x.jpg 3x" width="700" style="border: 1px solid grey; margin-bottom: 2em; margin-top: 1em"></a></p>
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<footer class="footer" style="text-align: center">
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<p>© 2017 gokrazy authors (Michael Stapelberg and contributors)</p>
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</footer>
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</div>
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</body>
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</html>
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</div>
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</body>
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</html>
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@ -57,6 +57,10 @@ GitHub</a>.</p>
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<ul>
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<li>
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<a href="https://gokrazy.org/userguide/gpio/">Controlling a GPIO input/output pin</a>
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</li>
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<li>
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<a href="https://gokrazy.org/userguide/remotesyslog/">Using Remote Syslog to send gokrazy logs over the network</a>
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</li>
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88
website/content/userguide/gpio.md
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88
website/content/userguide/gpio.md
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---
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title: "Controlling a GPIO input/output pin"
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weight: 10
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---
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# Controlling a GPIO input/output pin
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In this guide, we are using [periph.io](https://periph.io/), a library for
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peripheral I/O in Go, to set one of the Raspberry Pi’s General Purpose I/O
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(GPIO) pins to a logical high (3.3V) or low (0V) signal.
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periph.io supports the Raspberry Pi 3 and Raspberry Pi 4, starting with version
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`v3.6.4`.
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## Connect GPIO pins based on pinout
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<a href="https://pinout.xyz"><img src="/img/raspberry-pi-pinout.png" width="700" align="right" style="border: 1px solid grey; margin-bottom: 2em; margin-top: 1em"></a>
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To verify the code is doing what we expect, let’s connect a multimeter as per
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[pinout.xyz](https://pinout.xyz)’s pinout:
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* pin number 18 (signal `BCM24`, labeled `24` in the pinout above)
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* pin number 20 (signal `GND`)
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We need to set the multimeter to “Voltage measurement, DC (direct current)”.
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## Setting an output pin signal
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To set the pin high and low, alternatingly, with a 5 second frequency, we will
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be using the `hello-gpio` program, which is a slightly modified version of the
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example at [periph.io/device/led](https://periph.io/device/led/):
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```go
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package main
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import (
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"log"
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"time"
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"periph.io/x/periph/conn/gpio"
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"periph.io/x/periph/host"
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"periph.io/x/periph/host/rpi"
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)
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func doGPIO() error {
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log.Printf("Loading periph.io drivers")
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// Load periph.io drivers:
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if _, err := host.Init(); err != nil {
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return err
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}
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log.Printf("Toggling GPIO forever")
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t := time.NewTicker(5 * time.Second)
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for l := gpio.Low; ; l = !l {
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log.Printf("setting GPIO pin number 18 (signal BCM24) to %v", l)
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// Lookup a pin by its location on the board:
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if err := rpi.P1_18.Out(l); err != nil {
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return err
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}
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<-t.C
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}
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return nil
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}
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func main() {
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if err := doGPIO(); err != nil {
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log.Fatal(err)
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}
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}
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```
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Install the program on your Raspberry Pi using gokrazy (see [Quickstart](/quickstart/)):
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```shell
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gokr-packer \
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-update=yes \
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github.com/gokrazy/hello \
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github.com/gokrazy/breakglass \
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github.com/gokrazy/serial-busybox \
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github.com/gokrazy/hello-gpio
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```
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…and wait a few seconds for it to reboot.
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At this point, we should be able to see the high/low signal on the multimeter,
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alternating between 3.3V (high) and 0V (low) every 5 seconds:
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<a href="/img/2020-06-15-gpio.jpg"><img src="/img/2020-06-15-gpio.thumb.jpg" srcset="/img/2020-06-15-gpio.thumb.2x.jpg 2x,/img/2020-06-15-gpio.thumb.3x.jpg 3x" width="700" style="border: 1px solid grey; margin-bottom: 2em; margin-top: 1em"></a>
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@ -1,6 +1,6 @@
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---
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title: "Using Remote Syslog to send gokrazy logs over the network"
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weight: 10
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weight: 20
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---
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# Using Remote Syslog to send gokrazy logs over the network
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@ -1,6 +1,6 @@
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---
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title: "Using TLS in untrusted networks"
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weight: 20
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weight: 30
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---
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# Using TLS in untrusted networks
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@ -1,6 +1,6 @@
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---
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title: "Connecting to unencrypted WiFi networks"
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weight: 30
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weight: 40
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---
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# Connecting to unencrypted WiFi networks
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BIN
website/static/img/2020-06-15-gpio.jpg
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website/static/img/2020-06-15-gpio.jpg
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website/static/img/2020-06-15-gpio.thumb.2x.jpg
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website/static/img/2020-06-15-gpio.thumb.2x.jpg
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After Width: | Height: | Size: 283 KiB |
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website/static/img/2020-06-15-gpio.thumb.3x.jpg
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website/static/img/2020-06-15-gpio.thumb.3x.jpg
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BIN
website/static/img/2020-06-15-gpio.thumb.jpg
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BIN
website/static/img/2020-06-15-gpio.thumb.jpg
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After Width: | Height: | Size: 87 KiB |
BIN
website/static/img/raspberry-pi-pinout.png
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BIN
website/static/img/raspberry-pi-pinout.png
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After Width: | Height: | Size: 76 KiB |
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