DisplayPort: Tapping The Altmode

July 24, 2023 by Arya Voronova 11 Comments

Really, the most modern implementation of DisplayPort is the USB-C DisplayPort altmode, synonymous with “video over USB-C”, and we’d miss out if I were to skip it. Incidentally, our last two articles about talking USB-PD have given a few people a cool new toy to play with – people have commented on the articles, reached out to me for debugging help, and I’ve even seen people build the FUSB302B into their projects! Hot on the heels of that achievement, let’s reach further and conquer one more USB-C feature – one that isn’t yet openly available for us to hack on, even though it deserves to be.

For our long-time readers, it’s no surprise to see mundane capabilities denied to hackers. By now, we all know that many laptops and phones let you get a DisplayPort connection out of a USB-C port. Given that the USB-C specifications are openly available, and we’ve previously implemented a PD sink using those specifications, you’d expect that we could do DisplayPort with the same ease. Yet, the DisplayPort altmode specification is behind a VESA membership paywall, with a hefty pricetag – a practice of theirs that has been widely criticized, counter to their purpose as a standards organization and having resulted in some of their standards failing.

Not to worry, however – we can easily find an assortment of PDFs giving a high-level overview and some details of the DisplayPort altmode, and here’s my favorite! I also have a device running MicroPython with a FUSB302 chip connected, and a few DisplayPort altmode devices of mine that I can disassemble. This, turns out, is more than enough for us to reverse-engineer our way into an open-source DisplayPort altmode library!

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The BSides: More Curious Uses Of Off-the-shelf Parts

April 24, 2023 by Sonya Vasquez 10 Comments

Off-the-shelf stock parts are the blocks from which we build mechanical projects. And while plenty of parts have dedicated uses, I enjoy reusing them in ways that challenge what they were originally meant for while respecting the constraints of their construction. Building off of my piece from last time, I’d like to add to your mechanical hacking palette with four more ways we can re-use some familiar off-the-shelf parts. Continue reading “The BSides: More Curious Uses Of Off-the-shelf Parts” →

PCIe For Hackers: Extracting The Most

March 30, 2023 by Arya Voronova 25 Comments

So, you now know the basics of approaching PCIe, and perhaps you have a PCIe-related goal in mind. Maybe you want to equip a single-board computer of yours with a bunch of cheap yet powerful PCIe WiFi cards for wardriving, perhaps add a second NVMe SSD to your laptop instead of that Ethernet controller you never use, or maybe, add a full-size GPU to your Raspberry Pi 4 through a nifty adapter. Whatever you want to do – let’s make sure there isn’t an area of PCIe that you aren’t familiar of.

Splitting A PCIe Port

You might have heard the term “bifurcation” if you’ve been around PCIe, especially in mining or PC tinkering communities. This is splitting a PCIe slot into multiple PCIe links, and as you can imagine, it’s quite tasty of a feature for hackers; you don’t need any extra hardware, really, all you need is to add a buffer for REFCLK. See, it’s still needed by every single extra port you get – but you can’t physically just pull the same clock diffpair to all the slots at once, since that will result in stubs and, consequently, signal reflections; a REFCLK buffer chip takes the clock from the host and produces a number of identical copies of the REFCLK signal that you then pull standalone. You might have seen x16 to four NVMe slot cards online – invariably, somewhere in the corner of the card, you can spot the REFCLK buffer chip. In a perfect scenario, this is all you need to get more PCIe out of your PCIe.

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PCIe For Hackers: The Diffpair Prelude

March 14, 2023 by Arya Voronova 35 Comments

PCIe, also known as PCI-Express, is a highly powerful interface. So let’s see what it takes to hack on something that powerful. PCIe is be a bit intimidating at first, however it is reasonably simple to start building PCIe stuff, and the interface is quite resilient for hobbyist-level technology. There will come a time when we want to use a PCIe chip in our designs, or perhaps, make use of the PCIe connection available on a certain Compute Module, and it’s good to make sure that we’re ready for that.

PCIe is everywhere now. Every modern computer has a bunch of PCIe devices performing crucial functions, and even iPhones use PCIe internally to connect the CPU with the flash and WiFi chips. You can get all kinds of PCIe devices: Ethernet controllers, high-throughput WiFi cards, graphics, and all the cheap NVMe drives that gladly provide you with heaps of storage when connected over PCIe. If you’re hacking on a laptop or a single-board computer and you’d like to add a PCIe device, you can get some PCIe from one of the PCIe-carrying sockets, or just tap into an existing PCIe link if there’s no socket to connect to. It’s been two decades since we’ve started getting PCIe devices – now, PCIe is on its 5.0 revision, and it’s clear that it’s here to stay.

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A Hacker’s Introduction To DIY Light Guide Plates

March 13, 2023 by Sonya Vasquez 39 Comments

Last year, I found myself compelled to make a scaled-down replica of the iconic test chamber signs from the video game Portal. If you’ve played the game, you’ll remember these signs as the illuminated monoliths that postmarked the start of every test chamber. In hyperstylized video game fashion, they were also extremely thin.

https://www.thonky.com/portal-walkthrough/test-chamber-19 — Stay tuned for cake at the end of this article.

True to the original, my replica would need to be both slimmed down and backlit with a uniform, natural white glow. As fate would have it, the crux of this project was finding a way to do just that: to diffuse light coming in from the edges so that it would emit evenly from the front.

What I thought would be quick project ended up being a dive down the rabbit hole that yielded some satisfying results. Today, I’d like to share my findings and introduce you to light guide plates, one of the key building blocks inside of much of today’s backlit screen technology. I’ll dig into the some of the working principles, introduce you to my homebrew approach, and leave you with some inspirational source code to go forth and build your own. Continue reading “A Hacker’s Introduction To DIY Light Guide Plates” →

Laptop Motherboard? Let’s Boot And Tinker

March 7, 2023 by Arya Voronova 12 Comments

Last time, I’ve shared my experience on why you might want to consider a laptop motherboard for a project of yours, and noted some things you might want to keep in mind if buying one for a project. Now, let’s go through the practical considerations!

Making It Boot

Usually, when you plug some RAM and a charger into a board, then press the power button, your board should boot up and eventually show the BIOS on the screen. However, there will be some caveats – it’s very firmware-dependent. Let me walk you through some confusing situations you might encounter.

If the board was unpowered for a while, first boot might take longer – or it might power on immediately after a charger has been plugged in, and then, possibly, power off. A bit of erratic behaviour is okay, since boards might need to do memory training, or recover after having lost some CMOS settings. Speaking of those, some boards will not boot without a CMOS battery attached, and some will go through the usual ‘settings lost’ sequence. Sometimes, the battery will be on a daughterboard, other times, especially with new boards, there will be no CR2032 in sight and the board will rely on the main battery to provide CMOS settings saving functions – in such case, if you don’t use the battery, expect the first boot to take longer, at least. Overall, however, pressing the power switch will cause the board to boot. Continue reading “Laptop Motherboard? Let’s Boot And Tinker” →

Laptop Motherboard? No, X86 Single-Board Computer!

February 27, 2023 by Arya Voronova 47 Comments

Sometimes a Raspberry Pi will not cut it – especially nowadays, when the prices are high and the in-stock amounts are low. But if you look in your closet, you might find a decently-specced laptop with a broken screen or faulty hinges. Or perhaps someone you know is looking to get rid of a decent laptop with a shattered case. Electronics recycling or eBay, chances are you can score a laptop with at least some life left in it.

Let’s hack! I’d like to show you how a used laptop motherboard could be the heart of your project, and walk you through some specifics you will want to know.

And what a great deal it could be for your next project! Laptop motherboards can help bring a wide variety of your Linux- and Windows-powered projects to life, in a way that even NUCs and specialized SBCs often can’t do. They’re way cheaper, way more diverse, and basically omnipresent. The CPU can pack a punch, and as a rule PCIe, USB3, and SATA ports are easily accessible with no nonsense like USB-throttled Ethernet ports.

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