Here’s the thing about coding. When you’re working on embedded projects, it’s quite easy to run into hardware limitations, and quite suddenly, too. You find yourself desperately trying to find a way to speed things up, only… there are no clock cycles to spare. It’s at this point that you might reach for the magic of direct memory access (DMA). [Larry] is here to advocate for its use.
DMA isn’t just for the embedded world; it was once a big deal on computers, too. It’s just rarer these days due to security concerns and all that. Whichever platform you’re on, though, it’s a valuable tool to have in your arsenal. As [Larry] explains, DMA is a great way to move data from memory location to memory location, or from memory to peripherals and back, without involving the CPU. Basically, a special subsystem handles trucking data from A to B while the CPU gets on with whatever other calculations it had to do. It’s often a little more complicated in practice, but that’s what [Larry] takes pleasure in explaining.
Indeed, back before I was a Hackaday writer, I was no stranger to DMA techniques myself—and I got my project published here! I put it to good use in speeding up an LCD library for the Arduino Due. It was the perfect application for DMA—my main code could handle updating the graphics buffer as needed, while the DMA subsystem handled trucking the buffer out to the LCD quicksmart.
If you’re struggling with updating a screen or LED strings, or you need to do something fancy with sound, DMA might just be the ticket. Meanwhile, if you’ve got your own speedy DMA tricks up your sleeve, don’t hesitate to let us know!
Electricity can be a pretty handy tool when it stays within the bounds of its wiring. It’s largely responsible for our modern world and its applications are endless. When it’s not running in wires or electronics though, things can get much more complicated even for things that seem simple on the surface. For example, measuring moisture in soil seems straightforward, but corrosion presents immediate problems. To combat the problems with measuring things in the natural world with electricity, [David] built this capacitive soil moisture sensor which also has the benefit of using an extremely small amount of energy to operate.
The sensor is based on an STM32 microcontroller, in this case one specifically optimized for low-power applications. The other low-power key to this build is the small seven-segment e-ink display. The segments are oriented as horizontal lines, making this a great indicator for measuring a varying gradient of any type. The microcontroller only wakes up every 15 minutes, takes a measurement, and then updates the display before going back to sleep.
To solve the problem resistive moisture sensors have where they’re directly in contact with damp conditions and rapidly corrode, [David] is using a capacitive sensor instead which measures a changing capacitance as moisture changes. This allows the contacts to be much more isolated from the environment. The sensor has been up and running for a few months now with the coin cell driving the system still going strong and the house plants still alive and properly watered. Of course if you’re looking to take your houseplant game to the next level you could always build a hydroponics system which automates not only the watering of plants but everything else as well.
It’s 2025, and you’re still probably pressing modifier keys on your keyboard like a… regular person. But it doesn’t have to be this way! You could use foot pedals instead, as [Jan Herman] demonstrates.
Now, if you’re a diehard embedded engineer, you might be contemplating your favorite USB HID interface chip and how best to whip up a custom PCB for the job. But it doesn’t have to be that complicated! Instead, [Jan] goes for an old school hack—he simply ripped the guts out of an cheap USB keyboard. From there, he wired up a few of the matrix pads to 3.5 mm jack connectors, and put the whole lot in a little metal project box. Then, he hooked up a few foot pedal switches with 3.5 mm plugs to complete the project.
[Jan] has it set up so he can plug foot pedals in to whichever keys he needs at a given moment. For example, he can plug a foot pedal in to act as SPACE, ESC, CTRL, ENTER, SHIFT, ALT, or left or right arrow. It’s a neat way to make the project quickly reconfigurable for different productivity tasks. Plus, you can see what each pedal does at a glance, just based on how it’s plugged in.
Somewhere between the period of 1999 and 2007 a plague swept through the world, devastating lives and businesses. Identified by a scourge of electrolytic capacitors violently exploding or splurging their liquid electrolyte guts all over the PCB, it led to a lot of finger pointing and accusations of stolen electrolyte formulas. In a recent video by [Asianometry] this story is summarized.
The bad electrolyte in the faulty capacitors lacked a suitable depolarizer, which resulted in more gas being produced, ultimately leading to build-up of pressure and the capacitor ultimately failing in a way that could be rather benign if the scored top worked as vent, or violently if not.
Other critical elements in the electrolyte are passivators, to protect the aluminium against the electrolyte’s effects. Although often blamed on a single employee stealing an (incomplete) Rubycon electrolyte formula, the video questions this narrative, as the problem was too widespread.
More likely it coincided with the introduction of low-ESR electrolytic capacitors, along with computers becoming increasingly more power-hungry, and thus stressing the capacitors in a much warmer environment than in the early 1990s. Combine this with the presence of counterfeit capacitors in the market and the truth of what happened to cause the Capacitor Plague probably involves a bit from each column, a narrative that seems to be the general consensus.
Image by [StunningBreadfruit30] via redditHere’s the gist: this sexy split grid of beautiful multi-jet fusion (MJF) keycaps sits on top of Kailh PG1316S switches. The CNC-machined aluminium enclosure hides nice!nano boards with a sweet little dip in each one that really pull the keyboard together.
For the first serious custom build, [StunningBreadfruit30] wanted a polished look and finish, and to that I say wow, yes; good job, and nod enthusiastically as I’m sure you are. Believe it or not, [StunningBreadfruit30] came into this with no CAD skills at all. But it was an amazing learning experience overall, and an even better version is in the works.
I didn’t read the things. Is it open-source? It’s not, at least not at this time. But before you get too-too excited, remember that it cost $400 to build, and that doesn’t even count shipping or the tools that this project necessitated purchasing. However, [StunningBreadfruit30] says that it may be for sale in the future, although the design will have an improved sound profile and ergonomics. There’s actually a laundry list of ideas for the next iteration.
Image by [Saixos] via redditSo, it’s adjustable? Yes, in more ways than one. It can utilize either a single RP2040 Zero, or else one or multiple XIAO BLEs. The thumb cluster snaps off and can be moved wherever you like.
And [Saixos] didn’t stop there. In the magnificent repo, there’s a Python-generated case that’s highly customizable, plus MX and Choc versions of the PCB. Finally, Apiaster can use either LiPo batteries or a coin cell.
The other main crux of the biscuit here is price, and the Apiaster can be built for about $37 total minus shipping/customs/tariffs and/or tooling. That’s pretty darn good, especially if this really becomes your endgame.
The Centerfold: A ’90s Kid Works Here
Image by [nismology5] via redditAfter using a Durgod Taurus K320 rectangle for a number of years, [nismology5] decided to lean into ergo and acquired a Keychron Q8 with a knob and the Alice layout after falling in love with the look of GMK Panels keycaps and the Alice herself.
Perhaps the biggest change is going from clacky blues on the Taurus to silent and slinky reds. Who knows why such a drastic change, but [nismology5] is digging the smoothness and quietude underneath those GMK Panels clones from Ali.
Now, let’s talk about that sweet trackball. It’s a Clearly Superior Technologies (CST) KidTRAC with a pool ball swapped in. They are discontinued, sadly, but at least one was available as NOS on eBay. Not to worry — they are being produced by another company out of the UK and come in that sweet UNO Draw 4 Wild drip.
Do you rock a sweet set of peripherals on a screamin’ desk pad? Send me a picture along with your handle and all the gory details, and you could be featured here!
Historical Clackers: the Fox was Quite Fetching
The lovely Fox was named not for its primary inventor Glenn J. Barrett, but instead for company president William R. Fox. Although this may seem unfair, the Fox is a pretty great name for a good-looking typewriter.
This nineteenth-century Fox appeared in 1898, shortly after it was patented and had a number of nice features, like a notably light touch. The carriage can be removed easily for cleaning and maintenance. And the machine had a “speed escapement”, which affects the carriage advancement timing. It could be set to advance either when a typebar returns to rest, or as soon as the typebar starts off for the platen.
The first Foxes were understroke machines, which is another term for blind writer, meaning that one must lift something out of the way to see what one had written as the typebars strike the platen from underneath. In the case of the Fox, one need only turn the platen slightly.
Frontstroke or ‘visible’ typewriters were coming into vogue already, so the company introduced a frontstroke machine in 1906. It had many of the same features as the blind-writing Foxen, such as the dual-speed escapement. A one- or two-color ribbon could be used, and the machine could be set to oscillate the ribbon so as not to waste the entire bottom half as most typewriters did. I’d like to see it set to oscillate with a two-color ribbon, that’s for sure!
To capitalize on the portable craze, they built the so-called “Baby Fox” in 1917. Corona found the resemblance to their own portables quite striking and successfully sued Fox. The company went out of business in 1921, possibly because of this litigation. Ah, well.
Probably the best thing about these delicious-looking 3D-printed keycaps are the cheese knife Backspace, Enter, and right Shift along with the novelties like the mousy Esc. Underneath all that fromage is a Keychron V6 Max with unknown switches.
[RobertLobLaw2] explains that cheese and keyboards have more in common than you think, as both hobbies use ‘pretentious adjectives to describe the sensory experience (of the hobby)’. Boy, if that isn’t the thocking truth. Should you require such a charcuter-key board for yourself, the files are freely available.
There’s something that kills coding speed—iteration time. If you can smash a function key and run your code, then watch it break, tweak, and smash it again—you’re working fast. But if you have to first compile your code, then plug your hardware in, burn it to the board, and so on… you’re wasting a lot of time. It’s that problem that inspired [Larry] to create an embedded system simulator to speed development time for simple projects.
The simulator is intended for emulating Arduino builds on iPhone and Mac hardware. For example, [Larry] shows off a demo on an old iPhone, which is simulating an ESP32 playing a GIF on a small LCD display. The build isn’t intended for timing-delicate stuff, nor anything involving advanced low-level peripherals or sleep routines and the like. For that, you’re better off with real hardware. But if you’re working on something like a user interface for a small embedded display, or just making minor tweaks to some code… you can understand why the the simulator might be a much faster way to work.
For now, [Larry] has kept the project closed source, as he’s found that it wouldn’t reasonably be possible for him to customize it for everyone’s unique hardware and use cases. Still, it’s a great example of how creating your own tools can ease your life as a developer. We’ve seen [Larry]’s great work around here before, like this speedy JPEG decoder library. Continue reading “Simulating Embedded Development To Reduce Iteration Time”→
An Instruction Set Architecture (ISA) defines the software interface through which for example a central processor unit (CPU) is controlled. Unlike early computer systems which didn’t define a standard ISA as such, over time the compatibility and portability benefits of having a standard ISA became obvious. But of course the best part about standards is that there are so many of them, and thus every CPU manufacturer came up with their own.
Throughout the 1980s and 1990s, the number of mainstream ISAs dropped sharply as the computer industry coalesced around a few major ones in each type of application. Intel’s x86 won out on desktop and smaller servers while ARM proclaimed victory in low-power and portable devices, and for Big Iron you always had IBM’s Power ISA. Since we last covered the ISA Wars in 2019, quite a lot of things have changed, including Apple shifting its desktop systems to ARM from x86 with Apple Silicon and finally MIPS experiencing an afterlife in the form of LoongArch.
Meanwhile, six years after the aforementioned ISA Wars article in which newcomer RISC-V was covered, this ISA seems to have not made the splash some had expected. This raises questions about what we can expect from RISC-V and other ISAs in the future, as well as how relevant having different ISAs is when it comes to aspects like CPU performance and their microarchitecture.
