Hey Google, Is My Heart Still Beating?

March 23, 2021 by Tom Nardi 18 Comments

University of Washington researchers studying the potential medical use of smart speakers such as Amazon’s Echo and Google’s Nest have recently released a paper detailing their experiments with non-contact acoustic heartbeat detection. Thanks to their sensitive microphone arrays, normally used to help localize voice commands from the user, the team proposes these affordable and increasingly popular smart home gadgets could lead a double life as unobtrusive life sign monitors. The paper goes so far as to say that even with multiple people in the room, their technique can be used to monitor the heart and respiratory rate of a specific target individual.

Those are some bold claims, but they aren’t without precedent. Previous studies performed at UW in 2019 demonstrated how smart speaker technology could be used to detect cardiac arrest and monitor infant breathing. This latest paper could be seen as the culmination of those earlier experiments: a single piece of software that could not just monitor the vitals of nearby patients, but actually detect a medical emergency. The lifesaving potential of such a program, especially for the very young and elderly, would be incredible.

So when will you be able to install a heart monitor skill on the cheap Echo Dot you picked up on Prime Day? Well, as is often the case with this kind of research, putting the technique to work in the real-world isn’t nearly as easy as in the laboratory. While the concept is promising and is more than worthy of further research, it may be some time before our lowly smart speakers are capable of Star Trek style life-sign detection.

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Machine Learning Current Sensor Snoops On MCUs

March 23, 2021 by Tom Nardi 8 Comments

Anyone who’s ever tried their hand at reverse engineering a piece of hardware has wished there was some kind of magic wand you could tap on a PCB to understand what its doing and why. We imagine that’s what put security researcher [Mark C] on the path to developing CurrentSense-TinyML, a fascinating proof of concept that uses machine learning and sensitive current measurements to try and determine what a microcontroller is up to.

The idea is simple enough: just place a INA219 current sensor between the power supply and the microcontroller under observation, and record the resulting measurements as it goes about its business. Of course in this case, [Mark] knew what the target Arduino Nano was doing because he wrote the code that blinks its onboard LED.

This allowed him to create training data for TensorFlow, which was ultimately optimized into a model that could fit onto the Arduino Nano 33 BLE Sense which stands in for our magic wand. The end result is that the model can accurately predict when the Nano has fired up its LED based on the amount of power it’s using. [Mark] has done a fantastic job of documenting the whole process, which also doubles as a great intro for putting machine learning to work on a microcontroller.

Now we already know what you’re thinking: obviously the current would go up when the LED was lit, so the machine learning aspect is completely unnecessary. That may be true in this limited context, but remember, this is just a proof of concept to base further work on. In the future, with more training data, this technique could potentially be used to identify a whole range of nuanced activities. You’d be able to see when the MCU was sitting idle, when it was writing to flash, or when it was reading from sensors. In fact, with a good enough model, it might even be possible to identify the individual sensors that are being polled.

These are early days, but we’re very interested in seeing where this research goes. It might not be magic, but if analyzing the current draw of a coffee maker can tell you how much everyone in the office is drinking, then maybe it can help us figure out what all these unlabeled ICs are doing.

A Crash Course On Sniffing Bluetooth Low Energy

March 23, 2021 by Tom Nardi 26 Comments

Bluetooth Low Energy (BLE) is everywhere these days. If you fire up a scanner on your phone and walk around the neighborhood, we’d be willing to bet you’d pick up dozens if not hundreds of devices. By extension, from fitness bands to light bulbs, it’s equally likely that you’re going to want to talk to some of these BLE gadgets at some point. But how?

Well, watching this three part video series from [Stuart Patterson] would be a good start. He covers how to get a cheap nRF52480 BLE dongle configured for sniffing, pulling the packets out of the air with Wireshark, and perhaps most crucially, how to duplicate the commands coming from a device’s companion application on the ESP32.

The first video in the series is focused on getting a Windows box setup for BLE sniffing, so readers who aren’t currently living under Microsoft’s boot heel may want to skip ahead to the second installment. That’s where things really start heating up, as [Stuart] demonstrates how you can intercept commands being sent to the target device.

It’s worth noting that little attempt is made to actually decode what the commands mean. In this particular application, it’s enough to simply replay the commands using the ESP32’s BLE hardware, which is explained in the third video. Obviously this technique might not work on more advanced devices, but it should still give you a solid base to work from.

In the end, [Stuart] takes an LED lamp that could only be controlled with a smartphone application and turns it into something he can talk to on his own terms. Once the ESP32 can send commands to the lamp, it only takes a bit more code to spin up a web interface or REST API so you can control the device from your computer or other gadget on the network. While naturally the finer points will differ, this same overall workflow should allow you to get control of whatever BLE gizmo you’ve got your eye on.

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A Hi-Fi Speaker From Some Foil And Magnets

March 22, 2021 by Stephen Ogier 44 Comments

In the world of speakers, mass is the enemy of high frequency response. In order to get the crispest highs, some audiophiles swear by speakers in which the moving element is just a thin ribbon of metal foil. As the first step towards building a set of ribbon headphones, [JGJMatt] has designed a compact ribbon speaker made from aluminum foil.

A 3D-printed body holds six permanent magnets, which produce the static magnetic field necessary for the speaker to work. The sound itself is produced by a corrugated aluminum diaphragm made by taking a strip of foil and creasing it with a gear. Aluminum is difficult to solder, so electrical contact is made with a couple of short segments of copper tape. A little Blu Tack and glue hold it all together, and the result is stunning in its simplicity.

Check out the video after the break to hear how it sounds. If you want to try this yourself, it’s important to remember that ribbon speakers have very low input impedances (0.1 Ω for this design), so in order to prevent damage to your amplifier, a transformer or series resistor must be used to bring the impedance up to the 4-8 Ω your amplifier expects.

[JGJMatt] is no newcomer to exotic speaker technology—check out these thin distributed-mode loudspeakers they made! If you’re more interested in recording music than playing it, you might want to read about how a metal ribbon suspended in a magnetic field is used to make incredible microphones. Shout out to [Itay] for the tip. Continue reading “A Hi-Fi Speaker From Some Foil And Magnets” →

An Entire Game Inside Of A Font

March 22, 2021 by Kristina Panos 17 Comments

Where’s the last place you’d expect to be able to play a game on your computer? The word processing program? Image editor? How about your text editor? That’s right — you can fight your Fontemons in any program that makes use of fonts, because mad genius [Michael Mulet] has created a game that exists entirely within a single Open Type font file.

[Michael] has harnessed the power of ligatures to create a choose-your-own-adventure-style turn-based game that pokes fun at both Pokemon and various typeface names. You start by choosing between Papyromaniac, Verdanta, and Proggito and face off against enemies like Helvetikhan and Scourier.

This works because there are many ways to draw glyphs on a screen. [Michael] chose Type 2 Charstrings, which is a vector graphics format that Adobe created for PostScript. It can draw pixels with a series of move specifications that tell it to draw up, to the right, and then back down before closing off the pixel with an implicit operator that draws from the starting point to the ending point. [Michael] was able to create two shades of gray by drawing smaller versions of the pixels and making the image by combining white and black pixels.

If you just want to play the game, you can either download the .otf file or just try it out in the browser. You’re supposed to use ‘a’ and ‘b’ to make choices that advance the game, but we soon discovered that spamming other keys like ‘v’ and Enter will lead to strange places. If you play it straight, it takes about 20 minutes, but there are enough secrets built in to make it last five times as long. [Michael] was kind enough to create a tutorial for making font-based games, but if you just want to get going, the game engine is open source.

What other fun things can you do on that locked-down work computer? If it has Excel, you can use it to do animation or just kick back and watch a movie.

Build-It-Yourself LC Meter

March 22, 2021 by Stephen Ogier 31 Comments

A basic digital multimeter (DMM) is usually the first measurement tool the aspiring electronics tinkerer buys. Even a bargain-bin DMM will happily measure voltage, current, and resistance; check continuity; and may even have a mode to measure transistor gain. Every toolbox needs at least one DMM, but most have an crucial limitation— they can’t measure two of the fundamental electrical quantities: inductance and capacitance. On Hackaday.io, [core weaver] has developed an open-source LC meter to allow you to build your own tool to measure inductance and capacitance.

[core weaver]’s design is all through-hole, so even just assembling one would be a great exercise for someone getting started in electronics. However, he didn’t just release a design, in a series of videos he goes through the theory of the device’s operation; explains the design of the circuit, firmware, and case; and shows you how to put it all together. For times when you need to measure a lot of parts (e.g. if you have to sort a bag of cheap capacitors looking for specific value), he’s even developed a desktop program to save you some trouble!

The finished meter looks incredible! If you want to build one for yourself, he’s put all of the files up on GitHub, and we highly recommend you check out his first video after the break. If you’d like to build yourself a 6.5-digit DMM to go with our LC Meter, consider this one which even has a home-built ADC.

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Amazon Echo Gets Open Source Brain Transplant

March 22, 2021 by Tom Nardi 20 Comments

There’s little debate that Amazon’s Alexa ecosystem makes it easy to add voice control to your smart home, but not everyone is thrilled with how it works. The fact that all of your commands are bounced off of Amazon’s servers instead of staying internal to the network is an absolute no-go for the more privacy minded among us, and honestly, it’s hard to blame them. The whole thing is pretty creepy when you think about it.

Which is precisely why [André Hentschel] decided to look into replacing the firmware on his Amazon Echo with an open source alternative. The Linux-powered first generation Echo had been rooted years before thanks to the diagnostic port on the bottom of the device, and there were even a few firmware images floating around out there that he could poke around in. In theory, all he had to do was remove anything that called back to the Amazon servers and replace the proprietary bits with comparable free software libraries and tools.

Of course, it ended up being a little trickier than that. The original Echo is running on a 2.6.x series Linux kernel, which even for a device released in 2014, is painfully outdated. With its similarly archaic version of glibc, newer Linux software would refuse to run. [André] found that building an up-to-date filesystem image for the Echo wasn’t a problem, but getting the niche device’s hardware working on a more modern kernel was another story.

He eventually got the microphone array working, but not the onboard digital signal processor (DSP). Without the DSP, the age of the Echo’s hardware really started to show, and it was clear the seven year old smart speaker would need some help to get the job done.

The solution [André] came up with is not unlike how the device worked originally: the Echo performs wake word detection locally, but then offloads the actual speech processing to a more powerful computer. Except in this case, the other computer is on the same network and not hidden away in Amazon’s cloud. The Porcupine project provides the wake word detection, speech samples are broken down into actionable intents with voice2json, and the responses are delivered by the venerable eSpeak speech synthesizer.

As you can see in the video below the overall experience is pretty similar to stock, complete with fancy LED ring action. In fact, since Porcupine allows for multiple wake words, you could even argue that the usability has been improved. While [André] says adding support for Mycroft would be a logical expansion, his immediate goal is to get everything documented and available on the project’s GitLab repository so others can start experimenting for themselves.

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