Boot Your Pi Over USB

Historically, booting a Raspberry Pi required an SD card. However, if you follow [tynick’s] instructions, you can get a Pi 4 to boot from the USB port. Combine it with a small solid state disk drive, and you’ll get great performance, according to his post.

The caveat is this depends on a beta bootloader and, of course, you’ll still have to boot from an SD card at least once to load that bootloader. If you were deploying something serious, you’d probably want to make sure the bootloader is suitable for your needs.

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This Frequency Generator Knows How To Get Down

What kind of clever things could you do with a signal that had a period of 2 hours? Or 20? Any ideas? No seriously, tell us. Because [Joseph Eoff] has come up with a way to produce incredibly low frequency signals that stretch out for hours, and we’d love to figure out what we can do with it.

To be fair, it’s not like [Joseph] has any ideas either. He thought it would be an interesting project, and figures now that he has the technology, maybe some application will come to him. They say that if you’ve got a hammer everything looks like a nail, so maybe the next project he sends our way will be a sinusoidal fish feeder.

[Joseph] says doing the software side of things with Pure Data wasn’t a problem, but getting it out of the computer proved to be tricky. It turns out that your average computer sound card isn’t equipped to handle frequencies down into the millihertz range (big surprise), so they need to be coaxed out with some extra hardware. Using a simple circuit not unlike an AM demodulator, he’s able to extract the low-frequency signal from a 16 kHz carrier.

So if you ever find yourself in need of a handful of hertz, now you’ve got the tool to generate them. At least it’s more practical than how they used to generate low frequency signals back in the 1900s.

Herb Garden Is Smarter Than The Average… Garden

After 13 days, the herbs are showing good signs of growth.

Herbs are a great way to spice up any dish. Often they don’t need much, meaning that it’s possible to grow a useful amount in a fairly compact area. [Sunyecz22] wanted to do just that, so built a convenient indoor herb garden, giving it some smarts along the way.

The project is built around an Arduino Mega, a venerable stalwart of the scene that comes in handy on projects requiring plenty of digital I/O. It’s paired with four soil moisture sensors, one per planter pot to keep an eye on water levels. The system also controls LEDs which provide light based on the time of day to help the herbs grow. Finally, a tidy 3D printed enclosure gives the project a neat, finished look.

It’s a build that’s a straightforward way to get into automatic plant maintenance, and leaves plenty of scope for future work. With the capable Arduino Mega on hand, it would be a cinch to upgrade to automatic watering down the track. We’ve seen similar builds before, too. Video after the break.

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Secret Knock Unlocks Door

Watch any movie about the years of prohibition, and you’ll probably see character gain admittance to a speakeasy by using a secret knock on the door. In the old movies, a little sliding door would open so the doorman could check you out and let you in. With [IsmailSan’s] electronic lock, the secret knock automatically unlocks the door. You can see a video of how it works, below.

(Ed Note: Grrr…GitHub repo got pulled between writing and publication. Go check out the in-links in the bottom paragraph if you’re interested in knock-detectors.)

The device uses a piezoelectric speaker to detect the knocking. A speaker is a transducer and like many transducers, it will work — to some extent — in either direction. A servo motor manages the deadbolt. An Arduino runs the whole thing.

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FPGA Raises Component Video From A Sinclair ZX Spectrum

An abiding memory of the early-80s heyday of 8-bit computing for many is operating their computer from the carpet in front of the family TV. While the kids in the computer adverts had parents who bought them a portable colour telly on which to play Jet Set Willy, the average kid had used up all the Christmas present money on the computer itself. The cable would have been an RF connection to the TV antenna socket, and the picture quality? At the time we thought it was amazing because we didn’t know any different, but with the benefit of nearly 40 years’ hindsight, it was awful.

For ZX Spectrum owners in 2020 a standard modification is to bring out a composite video signal, but [c0pperdragon] has gone a step or two beyond that with a component video interface. And this isn’t a mod in which the signals are lifted from the Spectrum’s colour encoder circuitry, instead it uses an FPGA hooked directly to the ULA chip to generate the component video itself.

The Altera chip sits on a little PCB designed to occupy the footprint of the original Astec modulator, and sports a neat bundle of wires hooked up to the various Spectrum signals it needs. There are a couple of jumpers to select the output type and resolution, it supports YPbPr or RGsB outputs and both 288p and 576p. If you think perhaps it looks a little familiar, that’s because it’s the sister project of an earlier board for the Commodore 64. So if you have a Spectrum and are annoyed by UHF and PAL, perhaps it’s worth a look.

2020 Hackaday Prize Hack Chat With Majenta Strongheart

Join us on Wednesday, May 27 at noon Pacific for the 2020 Hackaday Prize Hack Chat with Majenta Strongheart!

It hardly seems possible, but the Hackaday Prize, the world’s greatest hardware design contest, is once more at hand. But the world of 2020 is vastly different than it was last year, and the challenges we all suddenly face have become both more numerous and more acute as a result. We’ve seen hackers rise to the challenges presented by the events of the last few months in unexpected ways, coming up with imaginative solutions and pressing the limits of what’s possible. What this community can do when it is faced with a real challenge is inspiring.

Now it’s time to take that momentum and apply it to some of the other problems the world is facing. For the 2020 Hackaday Prize, we’re asking you to throw your creativity at challenges in conservation, disaster response, assistive technology, and renewable resources. We’ve teamed up with leading non-profits in those areas, each of which has specific challenges they need you to address.

With $200,000 in prize money at stake, we’re sure you’re going to want to step up to the challenge. To help get you started, Majenta Strongheart, Head of Design and Partnerships at Supplyframe, will drop by the Hack Chat with all the details on the 2020 Hackaday Prize. Come prepared to pick her brain on what needs doing and how best to tackle the problems that the Prize is trying to address. And find out about all the extras, like the “Dream Team” microgrants, the wild card prize, and the community picks.

join-hack-chatOur Hack Chats are live community events in the Hack Chat group messaging. This week we’ll be sitting down on Wednesday, May 27 at 12:00 PM Pacific time. If time zones have got you down, we have a handy time zone converter.

Click that speech bubble to the right, and you’ll be taken directly to the Hack Chat group on You don’t have to wait until Wednesday; join whenever you want and you can see what the community is talking about.

Hacking The Road: Roundabouts

If you are from the US, you might be surprised at how prevalent roundabouts are in most of the world. Outside of Carmel, Indiana which has 125 roundabouts, these are pretty unusual in the United States though have been gaining in popularity over the past decade. It turns out, that while a modern roundabout is safer and more efficient than other intersection types, roundabouts got a bad rap early on and so the typical US driver still has a lot of anxiety when approaching one.

Prior to 1966, traffic circles were a spotty thing. In some cases, they were just big circular junctions. In others, the right-of-way rules were difficult to figure out or there were traffic lights and stop signs that did not lead to a better or safer driving experience.

Enter Frank Blackmore. In the UK, he introduced the “Priority Rule” which — simply — mandates that traffic entering a circle must give way to traffic already in the circle. Blackmore worked out that this method increases traffic flow by 10%. Although this kind of roundabout became law in the UK in 1966, the US was slow to adopt, primarily due to negative public opinion. In 2016, there were about 4,800 modern roundabouts in the U.S while France and the UK have roughly 55,000 combined.

So what are the virtues of the modern rounabout, and where did it come from? Let’s take a look.

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