Switching Regulator Layout For Dummies

Last time, we went over switching regulator basics – why they’re wonderful, how do you find a switching regulator chip for your purpose, and how to easily pick an inductor for one. Your datasheet should also tell you about layout requirements. However, it might not, or you might want to deviate from them – let’s go more in-depth on what those requirements are about.

Appreciate The Feedback

The two resistors on the right decide what your output voltage will be, and their output is noise-sensitive

There’s a few different switching regulator topologies. Depending on your regulator’s topology and how many components your chip contains, you might need some external components – maybe a Schottky diode, maybe a FET, or maybe even a FET pair. It’s often that the FET is built-in, and same goes for diodes, but with higher-current regulator (2 A to 3 A and above), it’s not uncommon to require an external one. For sizing up those, you’ll want to refer to the datasheet or existing boards.

Another thing is input and output capacitors – don’t skimp on those, because some regulators are seriously sensitive to the amount of capacitance they’re operating with. Furthermore, if you fail to consider things like capacitance dropping with voltage, you might make your regulator very unhappy – not that a linear regulator would be happy either, to be clear. We’ve covered an explainer on this recently – do check it out!

One thing you will likely need, is a feedback resistor divider – unless your switching regulator is pre-set for a certain voltage or is digitally controlled, you need to somehow point it to the right voltage, in an analog way. Quite a few switching regulators are set for a certain voltage output, but most of them aren’t, and they will want you to add a resistor divider to know what to output. There’s usually a formula for resistor divider calculation, so, pick a common resistor value, put it in as one of the resistors into the formula, get the other resistor value out of that formula, and see what’s the closest value you can actually buy. Don’t go below about 10 kΩ so that you don’t have unnecessary idle power consumption, but also don’t go too far above 100 kΩ to ensure good stability of the circuit. Continue reading “Switching Regulator Layout For Dummies”

To the left, a breadboard with the ATMega328P being attacked. To the right, the project's display showing multiple ;) smiley faces, indicating that the attack has completed successfully.

Glitching An ATMega328P Has Never Been Simpler

Did you know just how easily you can glitch microcontrollers? It’s so easy, you really have no excuse for not having tried it out yet. Look, [lord feistel] is doing glitching attacks on an ATMega328P! All you need is an Arduino board with its few SMD capacitors removed or a bare 328P chip, a FET, and some sort of MCU to drive it. All of these are extremely generic components, and you can quickly breadboard them, following [lord feistel]’s guide on GitHub.

In the proof-of-concept, you can connect a HD44780 display to the chip, and have the victim MCU output digits onto the display in an infinite loop. Inside of the loop is a command to output a smiley face – but the command is never reachable, because the counter is reset in an if right before it. By glitching the ATMega’s power input, you can skip the if and witness the ;) on your display; it is that simple.

What are you waiting for? Breadboard it up and see for yourself, this might be the method that you hack your next device and make it do your bidding. If the FET-and-MCU glitching starts to fail you at some point, there’s fancier tools you can use, like the ChipWhisperer. As for practical examples, [scanlime]’s elegant glitching-powered firmware hack is hard to forget.

Screenshot of the Kaby Lake CPU pinout next to the Coffee Lake CPU pinout, showing just how few differences there are

Intel’s Anti-Upgrade Tricks Defeated With Kapton Tape

If you own an Intel motherboard with a Z170 or Z270 chipset, you might believe that it only supports CPUs up to Intel’s 7th generation, known as Kaby Lake. Even the CPU socket’s pinout is different in the next generation — we are told, it will fit the same socket, but it won’t boot. So if you want a newer CPU, you’ll have to buy a new motherboard while you’re at it. Or do you?

Turns out, the difference in the socket is just a few pins here and there, and you can make a 8th or 9th generation Coffee Lake CPU work on your Z170/270 board if you apply a few Kapton tape fixes and mod your BIOS, in a process you can find as “Coffee Mod”. You can even preserve compatibility with the 6th/7th generation CPUs after doing this mod, should you ever need to go back to an older chip. Contrasting this to AMD’s high degree of CPU support on even old Ryzen motherboards, it’s as if Intel introduced this incompatibility intentionally.

There’s been a number of posts on various PC forums and YouTube videos, going through the process and showing off the tools used to modify the BIOS. Some mods are exceptionally easy to apply. For example, if you have the Asus Maximus VIII Ranger motherboard, a single jumper wire between two pads next to the EC will enable support without Kapton tape, a mod that likely could be figured out for other similar motherboards as well. There’s a few aspects to keep in mind, like making sure your board’s VRMs are good enough for the new chip, and a little more patching might be needed for hyper-threading, but nothing too involved.

Between money-grab features like this that hamper even the simplest of upgrades and increase e-waste, fun vulnerabilities, and inability to sort out problems like stability power consumption issues, it’s reassuring to see users take back control over their platforms wherever possible, and brings us back to the days of modding Xeon CPUs to fit into 775 sockets.

Don’t get too excited though, as projects like Intel BootGuard are bound to hamper mods like this on newer generations by introducing digital signing for BIOS images, flying under the banner of user security yet again. Alas, it appears way more likely that Intel’s financial security is the culprit.

Continue reading “Intel’s Anti-Upgrade Tricks Defeated With Kapton Tape”

How To Lace Cables Like It’s 1962

Cable harnesses made wire management a much more reliable and consistent affair in electronic equipment, and while things like printed circuit boards have done away with many wires, cable harnessing still has its place today. Here is a short how-to on how to lace cables from a 1962 document, thoughtfully made available on the web by [Gary Allsebrook] and [Jeff Dairiki].

It’s a short resource that is to the point in all the ways we love to see. The diagrams are very clear and the descriptions are concise, and everything is done for a reason. The knots are self-locking, ensuring that things stay put without being overly tight or constrictive.

According to the document, the ideal material for lacing cables is a ribbon-like nylon cord (which reduces the possibility of biting into wire insulation compared to a cord with a round profile) but the knots and techniques apply to whatever material one may wish to use.

Cable lacing can be done ad-hoc, but back in the day cable assemblies were made separately and electrically tested on jigs prior to installation. In a way, such assemblies served a similar purpose to traces on a circuit board today.

Neatly wrapping cables really has its place, and while doing so by hand can be satisfying, we’ve also seen custom-made tools for neatly wrapping cables with PTFE tape.

Lost Foam Casting In Action

Even though not all of us will do it, many of us are interested in the art of casting metal. It remains a process that’s not out of reach, though, especially for metals such as aluminium whose melting points are reachable with a gas flame. The video below the break takes us through the aluminium casting process by showing us the lost-foam casting of a cylinder head for a BSA Bantam motorcycle.

The foam pattern is CNC milled to shape, and the leftover foam swarf is removed with a hot wire. The pattern is coated with a refractory coating of gypsum slurry, and the whole is set up in a tub packed with sand. We get the impression that the escaping gasses make this a tricky pour without an extra sprue, and indeed, they rate it as not perfect. The cooling fins on the final head are a little ragged, so it won’t be the part that goes on a bike, but we can see with a bit of refining, this process could deliver very good results.

For this pour, they use a gas furnace, but we’ve seen it done with a microwave oven. Usually, you are losing wax, not foam, but the idea is the same.

Continue reading “Lost Foam Casting In Action”

DisplayPort: Hacking And Examples

So far, I’ve talked about why DisplayPort is the future, introduced the basics of how to work with it on the hacker level, took apart and tamed the DisplayPort altmode, and recently, went through the eDP (embedded DisplayPort) display technology. This time, I want to give you a project library to reference, so that your hacking goes as smoothly as possible – real-world examples of open-source DisplayPort boards, a few boards I’ve worked on, part numbers, and whatever other information you might need.

Even this wonderful build is not immune from wasting power on unnecessary video conversion

Over the past few years, I’ve noticed that a non-zero amount of cyberdeck builders buy eDP screens with HDMI converter boards on Aliexpress, then connect them to SBCs using USB-C to HDMI adapters, or ignore the onboard eDP port; even this super cool Framework-based cyberdeck has done that! I get that it’s the simplest option, but I do believe that you ought to know how to improve it. The issue is that this double-conversion decreases the battery life significantly by burning two extra ASICs doing video conversion back and forth. Every hour of battery life matters in a cyberdeck, doubly so if it’s based on a low-power device already – you could easily cut your battery life in half if you’re not careful!

With these projects and references in your arsenal, my aim is that DisplayPort becomes way more comfortable for you to work with. Thankfully, there are quite a few projects to reference by now – let’s delve in.

Right out of the gate – are you looking for an SBC with DisplayPort support? The BoardDB website, a database of single-board computers, has a DisplayPort filter – click this link with the filter already enabled and browse through.

Continue reading “DisplayPort: Hacking And Examples”

Think Again: Tips On Finding And Flexing Your Creativity

Technical work — including problem-solving — is creative work. In addition, creativity is more than a vague and nebulous attribute that either is or isn’t present when it’s needed. A short article by [Anthony D. Fredericks] gives some practical and useful tips on energizing and exercising one’s creativity.

Why would creative thinking be meaningful to a technical person? The author shares an anonymous observation that as children we’re taught to stay inside the lines, while as adults we are often expected to think outside the box. Certainly when it comes to technical tasks, our focus is more on logical thinking. But problem solving benefits as much from creative thinking as it does from more logical approaches.

How can one cultivate creative thinking? The main idea is that creativity is best flexed and exercised by actively looking for connections and similarities between highly dissimilar elements, rather than focusing on their differences. Some thought exercises are provided to help with this process. Like with any exercise, the more one does it, the better one becomes.

Practicing more creative thinking can help jolt new ideas and approaches to a tough problem, so give it a shot. It’s also worth keeping in mind that we all need a feeling of progress, especially during extended times of applying effort to something, so do yourself a favor and give yourself an occasional win.