Hiding Data In Music Might Be The Key To Ditching Coffee Shop WiFi Passwords

In a move guaranteed to send audiophiles recoiling back into their sonically pristine caves, two doctoral students at ETH Zurich have come up with an interesting way to embed information into music. What sounds crazy about this is that they’re hiding data firmly in the audible spectrum from 9.8 kHz to 10 kHz. The question is, does it actually sound crazy? Not to our ears, playback remains surprisingly ok.

You can listen to a clip with and without the data on ETH’s site and see for yourself. As a brief example, here’s twelve seconds of the audio presenting two versions of the same clip. The first riff has no data, and the second riff has the encoded data.

You can probably convince yourself that there’s a difference, but it’s negligible. Even if we use a janky bandpass filter over the 8 kHz -10 kHz range to make the differences stand out, it’s not easy to differentiate what you’re hearing:

After many years of performing live music and dabbling in the recording studio, I’d describe the data-encoded clip as having a tinny feedback or a weird reverb effect. However, you wouldn’t notice this in a track playing on the grocery store’s speaker. Continue reading “Hiding Data In Music Might Be The Key To Ditching Coffee Shop WiFi Passwords”

Driving A 16×2 LCD With Voltage Modulation

The basic 16×2 LCD is an extremely popular component that we’ve seen used in more projects than we could possibly count. Part of that is because modern microcontrollers make it so easy to work with; if you’ve got an I2C variant of the display, it only takes four wires to drive it. That puts printing a line of text on one of these LCDs a step or two above blinking an LED on a digital pin on the hierarchy of beginner’s electronics projects.

What’s that? Even four wires is too many? In that case, you might be interested in this hack from [Vinod] which shows how you can drive the classic 16×2 with data and power on the same pair of wires. You’ll still need a microcontroller “backpack” for the LCD to interpret the modulated voltage, but if you’ve got an application for a simple remote display, this is definitely worth checking out.

The basic idea is to “blink” the 5 V line so quick that a capacitor on the LCD side can float the electronics over the dips in voltage. As long as one of the pins of the microcontroller is connected to the 5 V line before the capacitor, it will be able to pick up when the line goes low. With a high enough data rate and a large enough capacitor as a buffer, you’re well on the way to encoding your data to be displayed.

For the transmitting side, [Vinod] is using a Python script on his computer that’s sending out the text for the LCD over a standard USB to UART converter. That’s fed into a small circuit put together on a scrap of perfboard that triggers a MOSFET off of the UART TX line.

We actually covered the theory behind this technique years ago, but it’s always interesting to see somebody put together a real-world example. There might not be too many practical uses for this trick in the era of dirt-cheap microcontrollers bristling with I/O, but it might make a fun gag at your hackerspace.

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Musical Mod Lets MRI Scanner Soothe The Frazzled Patient

Hackers love to make music with things that aren’t normally considered musical instruments. We’ve all seen floppy drive orchestras, and the musical abilities of a Tesla coil can be ear-shatteringly impressive. Those are all just for fun, though. It would be nice if there were practical applications for making music from normally non-musical devices.

Thanks to a group of engineers at Case Western Reserve University in Cleveland, there is now: a magnetic resonance imaging machine that plays soothing music. And we don’t mean music piped into the MRI suite to distract patients from the notoriously noisy exam. The music is actually being played through the gradient coils of the MRI scanner. We covered the inner working of MRI scanners before and discussed why they’re so darn noisy. The noise basically amounts to Lorenz forces mechanically vibrating the gradient coils in the audio frequency range as the machine shapes the powerful magnetic field around the patient’s body. To turn these ear-hammering noises into music, the researchers converted an MP3 of [Yo Yo Ma] playing [Bach]’s “Cello Suite No. 1” into encoding data for the gradient coils. A low-pass filter keeps anything past 4 kHz from getting to the gradient coils, but that works fine for the cello. The video below shows the remarkable fidelity that the coils are capable of reproducing, but the most amazing fact is that the musical modification actually produces diagnostically useful scans.

Our tastes don’t generally run to classical music, but having suffered through more than one head-banging scan, a half-hour of cello music would be a more than welcome change. Here’s hoping the technique gets further refined.

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ESP32 Makes For World’s Worst Radio Station

We can say one thing for [bitluni]: the BOMs for his projects, like this ESP32 AM radio transmitter, are always on the low side. That’s because he leverages software to do jobs traditionally accomplished with hardware, always with instructive results.

In this case, the job at hand is creating an RF oscillator in the broadcast AM band and modulating some audio onto it. From his previous experience using an ESP32 to watch video on an oscilloscope, [bitluni] knew that the microcontroller’s DACs were up to the task of producing an 800-kHz signal, and he managed to produce a more-or-less sine wave carrier with some clever code. His sketch takes data from a header file, modulates it onto the carrier, and sends it out over the ether using a short stub of wire for an antenna. The range is severely limited, but for what it is, it gets the job done and shows the basics. And as a bonus, [bitluni] included a bit of JavaScript that turns an audio file into a header file that’s ready to go out over the airwaves for all your trolling needs.

If you’re looking for a little more range for your low power transmitter and you’re a licensed amateur operator, you might want to explore the world of QRP radio.

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Why Is Donald Duck On The Radio? Math Behind Single Sideband Explained

AM, or amplitude modulation, was the earliest way of sending voice over radio waves. That makes sense because it is easy to modulate a signal and easy to demodulate it, as well. A carbon microphone is sufficient to crudely modulate an AM signal and diode — even a piece of natural crystal — will suffice to demodulate it. Outside of broadcast radio, most AM users migrated to single side band or SSB. On an AM receiver that sounds like Donald Duck, but with a little work, it will sound almost as good as AM, and in many cases better. If you want a better understanding of how SSB carries audio, have a look at [Radio Physics and Electronics] video on the subject.

The video covers the math of what you probably already know: AM has a carrier and two identical side bands. SSB suppresses the carrier and one redundant side band. But the math behind it is elegant, although you probably ought to know some trigonometry. Don’t worry though. At the end of the video, there’s a practical demonstration that will help even if you are math challenged.

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Reverse Engineering The Nintendo Wavebird

Readers who were firmly on Team Nintendo in the early 2000’s or so can tell you that there was no accessory cooler for the Nintendo GameCube than the WaveBird. Previous attempts at wireless game controllers had generally either been sketchy third-party accessories or based around IR, and in both cases the end result was that the thing barely worked. The WaveBird on the other hand was not only an official product by Nintendo, but used 2.4 GHz to communicate with the system. Some concessions had to be made with the WaveBird; it lacked rumble, was a bit heavier than the stock controllers, and required a receiver “dongle”, but on the whole the WaveBird represented the shape of things to come for game controllers.

Finding the center frequency for the WaveBird

Given the immense popularity of the WaveBird, [Sam Edwards] was somewhat surprised to find very little information on how the controller actually worked. Looking for a project he could use his HackRF on, [Sam] decided to see if he could figure out how his beloved WaveBird communicated with the GameCube. This moment of curiosity on his part spawned an awesome 8 part series of guides that show the step by step process he used to unlock the wireless protocol of this venerable controller.

Even if you’ve never seen a GameCube or its somewhat pudgy wireless controller, you’re going to want to read though the incredible amount of information [Sam] has compiled in his GitHub repository for this project.

Starting with defining what a signal is to begin with, [Sam] walks the reader though Fourier transforms, the different types of modulations, decoding packets, and making sense of error correction. In the end, [Sam] presents a final summation of the wireless protocol, as well as a simple Python tool that let’s the HackRF impersonate a WaveBird and send button presses and stick inputs to an unmodified GameCube.

This amount of work is usually reserved for those looking to create their own controllers from the ground up, so we appreciate the effort [Sam] has gone through to come up with something that can be used on stock hardware. His research could have very interesting applications in the world of “tool-assisted speedruns” or even automating mindless stat-grinding.

Mike Ossmann And Dominic Spill: IR, Pirates!

Mike Ossmann and Dominic Spill have been at the forefront of the recent wave of software-defined radio (SDR) hacking. Mike is the hardware guy, and his radio designs helped bring Bluetooth and ISM-band to the masses. Dominic is the software guy who makes sure that all this gear is actually usable. The HackRF SDR is still one of the best cheap choices if you need an SDR that can transmit and receive.

So what are these two doing on stage giving a talk about IR communication? Can you really turn traffic lights green by blinking lights? And can you spoof a TV remote with a cardboard cutout, a bicycle wheel, and a sparkler? What does IR have to do with pirates, and why are these two dressed up as buccaneers? Watch our video interview and find out, or watch the full talk for all of the juicy details.

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