A small round NRF51822 board glued to the underside of a mailbox lid, with a small vibration sensor attached

Check Your Mailbox Using The AirTag Infrastructure

When a company creates an infrastructure of devices, we sometimes subvert this infrastructure and use it to solve tricky problems. For example, here’s a question that many a hacker has pondered – how do you detect when someone puts mail into your mailbox? Depending on the availability of power and wireless/wired connectivity options, this problem can range from “very easy” to “impractical to solve”. [dakhnod] just made this problem trivial for the vast majority of hackers, with the FakeTag project – piggybacking off the Apple’s AirTag infrastructure.

This project uses a cheap generic CR2032-powered NRF51822 board, sending the mailbox status over the FindMy system Apple has built for the AirTag devices. For the incoming mail detection, he uses a simple vibration sensor, glued to the flap lid – we imagine that, for flap-less mailboxes, an optical sensor or a different kind of mechanical sensor could be used instead. Every time someone with a FindMy-friendly iPhone passes by [dakhnod]’s mailbox, he gets an update on its status, with a counter of times the sensor has been triggered. [dakhnod] estimates that the device could run for up to a year on a single battery.

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Illustrated Kristina with an IBM Model M keyboard floating between her hands.

Keebin’ With Kristina: The One With The Tri-lingual Typewriter

Isn’t it just fantastic when a project finally does what you wanted it to do in the first place? [Simon Merrett] isn’t willing to compromise when it comes to the Aerodox. His original vision for the keyboard was a wireless, ergonomic split that could easily switch between a couple of PCs. Whereas some people are more into making layout after layout, [Simon] keeps pushing forward with this same design, which is sort of a mashup between the ErgoDox and the Redox, which is itself a wireless version of the ErgoDox.

The Aerodox has three nRF51822 modules — one for the halves to communicate, one for the control half to send key presses, and a third on the receiver side. [Simon] was using two AA cells to power each one, and was having trouble with the range back to the PC.

The NRFs want 3.3 V, but will allegedly settle for 2 V when times are hard. [Simon] added a boost converter to give each a solid 3.3 V, and the Aerodox became reliable enough to be [Simon]’s daily driver. But let’s go back to the as-yet-unrealized potential part.

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Teardown: Orthofix SpinalStim

If you’ve ever had a particularly nasty fracture, your doctor may have prescribed the use of an electronic bone growth stimulator. These wearable devices produce a pulsed electromagnetic field (PEMF) around the bone, which has been shown to speed up the natural healing process in a statistically significant number of patients. That’s not to say there isn’t a debate about how effective they actually are, but studies haven’t shown any downsides to the therapy, so it’s worth trying at least.

Image from SpinalStim manual.

When you receive one of these devices, it will be programmed to only operate for a certain amount of time or number of sessions. Once you’ve “used up” the bone stimulator, it’s functionally worthless. As you might imagine, there’s no technical reason this has to be the case. The cynic would say the only reason these devices have an expiration date on them is because the manufacturer wants to keep them from hitting the second hand market, but such a debate is perhaps outside the scope of these pages.

The Orthofix SpinalStim you’re seeing here was given to me by a friend after their doctor said the therapy could be cut short. This provided a somewhat rare opportunity to observe the device before it deactivated itself, which I’d hoped would let me take a closer look at how it actually operated.

As you’ll soon see, things unfortunately didn’t work out that way. But that doesn’t mean the effort was fruitless, and there may yet be hope for hacking these devices should anyone feel like taking up the challenge.

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When A Bike Sharing Startup Goes Away, What Do You Do With The Bikes?

Part of the detritus of many cities over the last few years has been the ubiquitous bicycles and scooters of the various companies that offer them for hourly hire via a smartphone app. They’re annoying when left randomly on pavements by their users, and they sometimes appear to outnumber riders many times over. In 2018 for many cities outside China they became a little less numerous, as the Chinese bike sharing service Ofo contracted its operations and pulled its distinctive yellow machines from the streets. A couple of years later those Ofo bikes that were sold off or simply abandoned by the company and never recovered are still with us. They can be used if their lock is dismantled, but to do that is to ignore the potential of the lock. [Aladds] has written a firmware for Ofo locks that allows them to be unlocked by a code entered upon its buttons.

Onboard the lock are an nRF51822, 4G radio, and of course the lock mechanism itself. The battery is likely to be flat by now, and though he doesn’t tell us what it is it’s worth our pointing out that similar designs sometimes use hazardous LiSOCl2 chemistry which any hacker should be very cautious with. He gives us full instructions for finding the programming connections for the chip, which can either have its stock firmware downloaded for examination, or be wiped for insertion of the new version. To show the code in action there is also a short YouTube video that we’ve put below the break. Meanwhile we’ve peered inside an Ofo lock before, back in 2018.

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Fitness Tracker Hacked Into Optical Density Meter

What do fitness trackers have to do with bacterial cultures in the lab? Absolutely nothing, unless and until someone turns a fitness band into a general-purpose optical densitometer for the lab.

This is one of those stories that shows that you never know from where inspiration is going to come. [Chinna Devarapu] learned that as a result of playing around with cheap fitness bands, specifically an ID107HR. A community has built up around hacking these bands; we featured a similar band that was turned into an EEG. With some help, [Chinna] was able to reflash the microcontroller and program it in the Arduino IDE, and began looking for a mission for the sensor-laden platform.

He settled on building a continuous optical densitometer for his biology colleagues. Bacterial cultures become increasingly turbid as the grow, and measuring the optical density (OD) of a culture is a common way to monitor its growth phase. This is usually done by sucking up a bit of the culture to measure, but [Chinna] and his team were able to use the hacked fitness band’s heartrate sensor to measure the OD on the fly. The tracker fits in a 3D-printed holder where an LED can shine through the growing culture; the sensor’s photodiode measures the amount of light getting through and the raw data is available via the tracker’s Bluetooth. The whole thing can be built for less than $20, and the plans have been completely open-sourced.

We really like the idea of turning these fitness bands into something completely different. With the capabilities these things pack into such a cheap and compact package, they should start turning up in more and more projects.

A Cloned Bluetooth Tracker Meets Its Maker

The holidays bring us many things. Family and friends are a given, as is the grand meal in which we invariably overindulge. It’s a chance for decades old songs and movies to somehow manage to bubble back up to the surface, and occasionally a little goodwill even slips in here or there. But perhaps above all, the holidays are a time for every retailer to stock themselves to the rafters with¬†stuff. Do you need it? No. Do they want it? No. But it’s there on display anyway, and you’re almost certainly going to buy it.

Which is precisely how I came to purchase a two pack of Bluetooth Low Energy (BLE) “trackers” for the princely sum of $10 USD. I didn’t expect much out of them for $5 each, but as this seemed an exceptionally low price for such technology in a brick and mortar store, I couldn’t resist. Plus there was something familiar about the look of the tracker that I couldn’t quite put my finger on while I was still in the store.

That vague feeling of recollection sent me digging through my parts bin as soon as I got home, convinced that I had seen something among the¬†detritus that reminded me of my latest prize. Sure enough, I found a “Cube” Bluetooth tracker which, ironically, I had received as a Christmas gift some years ago. Putting them side by side, it was clear that the design of these “itek” trackers took more than a little inspiration from the better known (and five times as expensive) product.

The Cube was a bit thicker, but otherwise the shape, size, and even button placement on the itek was nearly identical. Reading through their respective manuals, the capabilities also seemed in perfect parity, down to being able to use the button on the device as a remote camera control for your smartphone. Which got me thinking: just how similar would these two devices be internally? Clearly they looked and functioned the same, but would they be built the same as well? They would have to cut costs somewhere.

Determined to find out how a company can put out what for all the world looks like a mirror image of a competitor’s device while undercutting them by such a large margin, I cracked both trackers open to get a bit more familiar with what makes them tick. What I found on closer inspection of these two similar gadgets is perhaps best summarized by that age old cautionary adage: “Don’t judge a book by its cover.”

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Germans React To UK’s Micro:bit

Getting kids interested in programming is all the rage right now, and the UK is certainly taking pole position with its BBC micro:bit, just recently distributed to every seventh-grader in the land. Germany, proud of its education system and technological prowess, is caught playing catch-up. Until now.

The Calliope Mini (translated here) is essentially a micro:bit clone, but one that has learned from the experience of its spiritual forefather — the connection points are spread around the outside of the board where the crocodile clips won’t accidentally touch each other.

Not content to simply copy, the Calliope also adds additional functionality. A microphone and speaker are integrated onboard, as is a Grove-style I2C connector. They’ve even added a TI DRV8837 H-bridge motor driver, so students could make a rolling robot straight out of the box.

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