Mixing Up Your Own Supersized Sidewalk Chalk

When folks started quarantining, chalk art spilled onto driveways and sidewalks to remind us that there’s still beauty and creative people doing what they always do. Now it’s time to strut your stuff and show your neighbors that things are greener on your slab of concrete. [friedpotatoes] has shared their giant sidewalk recipe with the world so you can paint the town red. With chalk.

Name brand sidewalk chalk is expensive considering how easy it is to make. What Big Chalk doesn’t want you to know is that the ingredients are just water, plaster of Paris, and tempera paint; meaning this project should be safe enough for the junior hackers to get some hands-on time. Some folks use food coloring instead of paint, but we know what happens to clothing when kids get their mitts on food coloring. [friedpotatoes] also includes extensive repurposing of recyclables, which is commendable.

The instructions suggest filling potato chip (crisp) tubes through a milk jug funnel to make giant pieces, but you can use any mold you like. If you have a CNC machine, it should be no trouble to make stamp-like pieces of chalk for tagging on the go, or shapes like arrows when you have to direct a miniature parade.

For permanent and precise sidewalk decorations, you can check out a graffiti paint machine and for totally temporary messages there is a water-dispensing writer.

Fire Pit Burns To The Beat With Bluetooth

Humans have several primal fascinations and perhaps two of the biggest ones are fire and music. While you can picture some cavemen and cavewomen sitting around a fire beating on sticks for rhythm, we think they’d be impressed if the fire danced along with the music. Through the power of Bluetooth, that’s exactly what [Random Tech DIY’s] new fire pit does.

Technically, this is called a Rubens tube, and while it’s an old technology, the Bluetooth is a certainly a modern touch. As you might expect, most of this project is workshop time, cutting MDF and plastic. The audio system is off-the-shelf and drives some car stereo speakers. The results looked good, and although it always makes us nervous building things that carry propane gas, it seems to work well enough from where we’re sitting.

We had to wonder what things you could change that would affect the display. Changing the number of holes, the diameter of the holes, or the gas pressure, for example, would certainly change how the flames look and react to the sound waves.

We have seen other Rubens tube projects, of course. However, we were really interested in the use of these as crude oscilloscopes before the availability of cathode ray tubes. We’ve seen a modern take on that, too.

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Exotic Device Gets Linux Support Via Wireshark And Rust

What can you do if you have a nice piece of hardware that kinda works out of the box, but doesn’t have support for your operating system to get the full functionality out of it? [Harry Gill] found himself in such a situation with a new all-in-one (AIO) water cooling system. It didn’t technically require any operating system interaction to perform its main task, but things like settings adjustments or reading back statistics were only possible with Windows. He thought it would be nice to have those features in Linux as well, and as the communication is done via USB, figured the obvious solution is to reverse engineer the protocol and simply replicate it.

His first step was to set up a dual boot system (his attempts at running the software in a VM didn’t go very well) which allowed him to capture the USB traffic with Wireshark and USBPcap. Then it would simply be a matter of analyzing the captures and writing some Linux software to make sense of the data. The go-to library for USB tasks would be libusb, which has bindings for plenty of languages, but as an avid Rust user, that choice was never really an issue anyway.

How to actually make use of the captured data was an entirely different story though, and without documentation or much help from the vendor, [Harry] resorted to good old trial and error to find out which byte does what. Eventually he succeeded and was able to get the additional features he wanted supported in Linux — check out the final code in the GitHub repository if you’re curious what this looks like in Rust.

Capturing the USB communication with Wireshark seems generally a great way to port unsupported features to Linux, as we’ve seen earlier with an RGB keyboard and the VGA frame grabber that inspired it. If you want to dig deeper into the subject, [Harry] listed a few resources regarding USB in general, but there’s plenty more to explore with reverse engineering USB.

Want To Support Hacker-friendly Hardware Design? Follow Valve’s Example

It’s been just over a year since Valve released Index, their flagship VR system, and it’s worth looking back at this GitHub repository as a fine example of how to provide supporting materials to a hacker-friendly hardware design. The image above shows off one of the hacker-friendly design elements: an empty space behind the visor, with a USB port off to the right, that exists for no reason other than to make it easier to mount and plug in whatever one might come up with. There’s more to it than that, however. If one wishes to provide supporting materials for a hardware design, one could certainly do worse than emulate Valve’s example.

The violet 3D model shows the area that modifications can occupy without getting in the way of any sensors.

The hardware repository contains not just CAD models of mod-friendly hardware pieces (both in high-resolution STEP models as well as STL files) but also 3D models of the sensor zones, so modders can ensure they avoid occluding any sensors with their creations. Examples are great, and one provided by Valve is the Booster; a hand controller add-on providing extra comfort for people with large hands or long thumbs. The model also doubles as a reference for designing attachments that will not interfere with any of the tracking or touch-sensitive surfaces of the controllers.

Being hacker-friendly doesn’t mean the hardware has no warranty, but it does mean that there is concrete guidance on what does or doesn’t risk voiding it. In the case of the Index hardware, the guidance is simple: “Anything that requires a T5 or smaller is not user serviceable.”

To us, the whole attitude of being hacker-friendly is exemplified by a statement about the headstrap, found about half-way down the page. The words “removing the headstrap is not recommended” are followed immediately by clear directions on how to do exactly that, demonstrating the kind of trust necessary to reduce barriers for add-ons and modifications. That is a great way to help foster experimentation, like this project for 1:1 mapping of physical elements to their VR counterparts, to make awesome spaceship cockpits.

Bike Computer Powers On Long After Your Legs Give Out

A typical bicycle computer from the store rack will show your speed, trip distance, odometer, and maybe the time. We can derive all this data from a magnet sensor and a clock, but we live in a world with all kinds of sensors at our disposal. [Matias N.] has the drive to put some of them into a tidy yet competent bike computer that has a compass, temperature, and barometric pressure.

The brains are an STM32L476 low-power controller, and there is a Sharp Memory LCD display as it is a nice compromise between fast refresh rate and low power. E-paper would be a nice choice for outdoor readability (and obviously low power as well) but nothing worse than a laggy speedometer or compass.

In a show of self-restraint, he didn’t try to replace his mobile phone, so there is no GPS, WiFi, or streaming music. Unlike his trusty phone, you measure the battery life in weeks, plural. He implemented EEPROM memory for persistent data through power cycles, and the water-resistant board includes a battery charging circuit for easy topping off between rides.

When you toss the power of a mobile phone at a bike computer, someone will unveil the Android or you can measure a different kind of power from your pedals.

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ESP32 Altair Emulator Gets Split Personality

If you wanted me to demo CP/M running on an emulated Altair 8800, I’d pull out a tiny board from my pocket. You might wonder how I wound up with an Altair 8800 that runs CP/M (even WordStar), that fits in your pocket and cost less than $10. Turns out it’s a story that goes back to 1975.

When the Altair 8800 arrived back in 1975, I wanted one. Badly. I’d been reading about computers but had no hands-on experience. But back then, as far as I was concerned, the $400 price tag might as well have been a million bucks. I was working for no real pay in my family’s store, though in all fairness, adjusted into today’s money that was about $2,000.

I’d love to buy one now, but a real Altair costs even more today than it did back then. They also take up a lot of desk space. Sure, there are replicas and I’ve had a few. I even helped work the kinks out of Vince Briel’s clone which I’ve enjoyed. However, the Briel computer has two problems. First, it takes a little work to drive a serial port (it uses a VGA and a PS/2 keyboard). Second, while it’s smaller than a real Altair, it is still pretty large — a byproduct of its beautiful front panel.

So to quickly show off CP/M to someone, you need to haul out a big box and find a VGA monitor and PS/2 keyboard — both of which are becoming vanishing commodities. I made some modifications to get the serial port working, but it is still a lot to cart around. You could go the software route with a simulator like SIMH or Z80pack, but now instead of finding a VGA monitor and a PS/2 keyboard, you need to find a computer where you can install the software. What I really wanted was a simple and portable device that could boot CP/M.

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Print Your Way To Keyboard Stability

Keyboard key stabilizers, or stabs as they’re known in enthusiast circles, do exactly what you’d expect — they stabilize longer keys like the Shifts and the space bar so that they don’t have to be struck dead-center to actuate evenly. Stabs work by flanking the key switch with two non-functional switch actuators linked with a thick wire bar. Some people love stabs and insist on stabilizing every key that’s bigger than 1u, while other people think  stabs are more trouble than they’re worth for various reasons, like rattling.

[Riskable 3D Printing] has been working on a parametric, printable stabilizer system for Cherry MX caps that uses small disk magnets to keep the wire in place. As you can see in the video (embedded after the break), the result is a crisp clacker that doesn’t rattle. The magnets stabilize the wire, so it snaps back quite nicely.

Although the print is an easy one, [Riskable] says the design process wasn’t as cut and dried as it seems. The center points of the stabilizer stems aren’t supposed to be in the center of cutouts, even though it looks that way to the naked eye. After that, the pain point has shifted to the wire, and getting it as straight as possible before making the necessary bends. [Riskable] is going to make a straightener to help out, and we suggest something like this one.

Clacker hacking is quite the rabbit hole, especially when combined with 3D printing. We recently saw a completely 3D-printed macro pad, springs and all.

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