Summary: <p>USB 3.2 testing is darn hard! We talk compliance test specs, USB 3.2 testing BKMs, and pre-spec silicon. Guest Jit Lim sits down with Mike Hoffman and Daniel Bogdanoff to talk about the new difficulties engineers are facing as they develop USB 3.2 silicon.</p> <div class="jetpack-video-wrapper"></div> <p> </p> <audio class="wp-audio-shortcode" id="audio-1950-1" style="width: 100%;"><a href="https://eestalktech.com/wp-content/uploads/2018/08/The-Huge-Challenge-of-Testing-USB-3.2-Electrical-Engineering-Podcast-33.mp3">https://eestalktech.com/wp-content/uploads/2018/08/The-Huge-Challenge-of-Testing-USB-3.2-Electrical-Engineering-Podcast-33.mp3</a></audio> <p>Agenda:</p> <p>In the last <a href="https://www.eestalktech.com">electrical engineering podcast</a>, we talked about how<a href="https://eestalktech.com/usb-3-2/"> USB 3.2 </a>runs in x2 mode (“by two”)</p> <p>This means there’s a lot of crosstalk. The <a href="https://eestalktech.com/usb-type-c/">USB Type C</a> connector is great, but its small size and fast edges means crosstalk is a serious concern.</p> <p>When we test USB, we want to emulate real-world communications. This means you have to check, connect, and capture signals from four lanes.</p> <p>For testing Thunderbolt you always have to do this, too.</p> <p>Early silicon creators and early adopters are already creating IP and chips for a spec that isn’t released yet.</p> <p>2:00 They’re testing based on the BKM (Best Known Method)</p> <p>3:30 Jit was just at Keysight World Japan, where many people presented BKMs for current technologies. Waiting for a test spec to be released is not an excuse for starting to work on a technology.</p> <p>4:50 How many companies are actually developing USB 3.2 products? The answer isn’t straightforward – the ecosystem is very complex and there are multiple vendors for a single system (like a cable).</p> <p>6:30 Many USB silicon vendors will develop an end-product and get it certified to prove that their silicon will work. They then sell the silicon and IP to other companies for use in their products.</p> <p>7:50 Daniel listened to an interesting podcast about how Monoprice reverse engineers complex products and sells them for cheaper:<br> https://www.npr.org/sections/money/2014/11/28/366793693/episode-586-how-stuff-gets-cheaper</p> <p>9:40 There are some BNC cables at the Keysight Colorado Springs site that were literally wire pulled and built in the building.</p> <p>10:00 Has anything changed as USB technology advances? There are a lot of new challenges – multiple challenges, retimers, multiple test modes</p> <p>Testing retimers is nontrivial, they are full receivers and full transmitter.</p> <p>11:30 When a new spec is developed, what does that look like? How far does the test group go when setting a new spec?</p> <p>The spec doesn’t look at how to test, it just looks it what it should do.</p> <p>Then, there’s a compliance test specification (CTS). This is developed by a test group, that looks at how things should be tested.</p> <p>So, there are two groups. the first asks “what should the spec be?” and the second asks “how do we test that group?”</p> <p>13:30 How many people are testing USB 3.2? Even though the compliance test specification is not developed yet? There are non being shipped, but there is a lot of activity!</p> <p>14:30 What are the main challenges? Basics. When you have 10 Gbps over copper on a PCB, people are failing spec! There are issues with some devices passing only intermittently. Especially over long cables and traces.</p> <p>15:45 Cheap PCBs make things even more tricky. So, there’s very</p>
