Shellcode Over MIDI? Bad Apple On A PSR-E433, Kinda

January 23, 2025 by Elliot Williams 6 Comments

If hacking on consumer hardware is about figuring out what it can do, and pushing it in directions that the manufacturer never dared to dream, then this is a very fine hack indeed. [Portasynthica3] takes on the Yamaha PSR-E433, a cheap beginner keyboard, discovers a shell baked into it, and takes it from there.

[Portasynthinca3] reverse engineered the firmware, wrote shellcode for the device, embedded the escape in a MIDI note stream, and even ended up writing some simple LCD driver software totally decent refresh rate on the dot-matrix display, all to support the lofty goal of displaying arbitrary graphics on the keyboard’s dot-matrix character display.

Now, we want you to be prepared for a low-res video extravaganza here. You might have to squint a bit to make out what’s going on in the video, but keep in mind that it’s being sent over a music data protocol from the 1980s, running at 31.25 kbps, displayed in the custom character RAM of an LCD.

As always, the hack starts with research. Identifying the microcontroller CPU lead to JTAG and OpenOCD. (We love the technique of looking at the draw on a bench power meter to determine if the chip is responding to pause commands.) Dumping the code and tossing it into Ghidra lead to the unexpected discovery that Yamaha had put a live shell in the device that communicates over MIDI, presumably for testing and development purposes. This shell had PEEK and POKE, which meant that OpenOCD could go sit back on the shelf. Poking “Hello World” into some free RAM space over MIDI sysex was the first proof-of-concept.

The final hack to get video up and running was to dig deep into the custom character-generation RAM, write some code to disable the normal character display, and then fool the CPU into calling this code instead of the shell, in order to increase the update rate. All of this for a thin slice of Bad Apple over MIDI, but more importantly, for the glory. And this hack is glorious! Go check it out in full.

MIDI is entirely hacker friendly, and it’s likely you can hack together a musical controller that would wow your audience just with stuff in your junk box. If you’re at all into music, and you’ve never built your own MIDI devices, you have your weekend project.

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A Ribbon Microphone Is Harder Than You Think

January 22, 2025 by Jenny List 21 Comments

There’s a mystique around ribbon microphones due to their being expensive studio-grade items, which has led more than one experimenter down the rabbit hole of making one. [Catherine van West] has posted her experiments in the field, and it makes for an interesting read.

The recipe for a ribbon microphone is very simple indeed — suspend a corrugated ribbon of foil in a magnetic field, and take the voltage across the ribbon. But that simplicity hides some significant issues, as the foil is much thinner than the stuff you might roast your turkey under. Such lightweight foil is extremely fragile, and the signwriters leaf used here proved to be difficult to get right.

Then when the microphone is built there’s still the exceptionally low impedance and small voltage across the ribbon to contend with. The choice here is a transformer rather than a FET preamp, which surprised us.

The result is by all accounts a decent sounding microphone, though with some hum pickup due to difficulty with shielding. Should you give one a try? Maybe not, but that hasn’t stopped others from giving it a go.

Family Bass Is Musical NES Magic

January 21, 2025 by Lewin Day 6 Comments

The Family BASIC keyboard was a peripheral that was built for programming on the Nintendo Family Computer, or Famicom. As [Linus Åkesson] demonstrates, though, it can do so much more. Meet the Family Bass.

The core of the project is a special adapter which [Linus] created to work with the Family BASIC keyboard. Traditionally, the keyboard plugs into the Famicom’s expansion port, but [Linus] wanted to hook it up to the controller port on a Nintendo Entertainment System instead. Getting them to talk was achieved with an ATtiny85 which could cycle through the 72-key matrix in the keyboard and spit out a serial stream of data the controller port could understand.

On the NES end, the console is set up to run custom code from [Linus] that lets him play the internal sound chip’s triangle wave with the keyboard. He demonstrates this ably in a video where he performs a song called Platform Hopping along with some of his other retro computer instruments.

We’ve seen [Linus] build some other great instruments in the past too, which are both creative and nostalgic. Video after the break.

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Cyber Walkman Does It In Style

January 21, 2025 by Kristina Panos 20 Comments

One of the best things about adulthood is that finally we get to, in most cases, afford ourselves the things that our parents couldn’t (or just didn’t for whatever reason). When [Yakroo108] was a child, Walkmans were expensive gadgets that were out of reach of the family purse. But today, we can approximate these magical music machines ourselves with off-the-shelf hardware.

Besides the cyberpunk aesthetic, the main attraction here is the UNIHIKER Linux board running the show. After that, it’s probably a tie between that giant mystery knob and the super-cool GUI made with Tkinter.

We also like the fact that there are two displays: the smaller one on the SSD1306 OLED handles the less exciting stuff like the volume level and the current time, so that the main UNIHIKER screen can have all the equalizer/cyberpunk fun.

Speaking of, this user-friendly GUI shows play/stop buttons and next buttons, but it looks like there’s no easy way to get to the previous track. To each their own, we suppose. Everything is enclosed in a brick-like 3D-printed enclosure that mimics early Walkmans with orange foam headphones.

If you want an updated Walkman with keyboard switches (who wouldn’t?), check this out.

Close up of a Sony FX-300 'Jackal' radio

Packing Even More Features Into A Classic Radio

January 17, 2025 by Heidi Ulrich 11 Comments

When it comes to hacking niches, breathing new life into vintage devices is always an exciting challenge. [t0mg]’s recent project exemplifies this with his 1978 Sony FX-300 ‘Jackal’ radio. He’d already upgraded the radio in 2021 and turned it into a feature-packed marvel, but there’s always room for improvement.

[t0mg]’s initial 2021 build had its quirks: noisy sound, a subpar display, and a non-functional radio module. Determined to enhance these aspects, he sourced an IPS version of the original 3.2″ ILI9431 LCD, significantly improving viewing angles. To tackle the audio issues, he integrated an M5Stack Atom microcontroller, utilizing its Bluetooth A2DP capabilities to deliver cleaner digital sound via I2S to the Teensy audio board. The Teensy itself got a complete wire overhaul just for the sake of good craftmanship.

The new setup also enabled the display of song metadata. Additionally, [t0mg] incorporated a dedicated Arduino Nano clone to manage inputs, streamlining the overall design. The revamped ‘Jackal’ now boasts a bunch of impressive features such as displaying RDS data for FM stations, voice recording, and an NFC reader for personalized playlists.

If you’re into radio makeovers, look into this post for a real golden oldie, or start out with the basics. For [t0mg]’s earlier improved version of this Jackal, read our article on it here.

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Piezo Buzzer Makes A Drum

January 15, 2025 by Jenny List 6 Comments

The humble piezo disc buzzer is much more than something that makes tinny beeps in retro electronic equipment, it can also be used as a sensor. Tapping a piezo buzzer gives an interesting waveform, with a voltage spike followed by an envelope, and then a negative rebound voltage. It’s something [Igor Brichkov] is using, to make a simple but effective electronic drum.

First of all, the output of the buzzer must be tamed, which he does by giving it a little impedance to dissipate any voltage spikes. There follows some simple signal conditioning with passive components, to arrive at an envelope for the final drum sound. How to turn a voltage into a sound? Using a voltage controlled amplifier working on a noise source. The result is recognizably the drum sound, entirely in electronics.

In a world of digital music it’s easy to forget the simpler end of sound synthesis, using circuits rather than software. If you hanker for the Good Old Days, we have an entire series on logic noise, doing the job with 4000 series CMOS logic.

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Cassette Tape Plays MP3s

January 6, 2025 by Bryan Cockfield 65 Comments

Cassette tapes were a major way of listening to (and recording) music througout the 1980s and 1990s and were in every hi-fi stereo, boom box, and passenger vehicle of the era. Their decline was largely as a result of improvements in CD technology and the rise of the MP3 player, and as a result we live in a world largely absent of this once-ubiquitous technology. There are still a few places where these devices crop up, and thanks to some modern technology their capabilities as a music playback device can be greatly enhanced.

The build starts, as one might expect, by disassembling the cassette and removing the magnetic tape from the plastic casing. With the interior of the cassette empty it’s capable of holding a small battery, USB-C battery charger, and a Bluetooth module. The head of an old tape deck can be wired to the audio output of the Bluetooth module and then put back in place in the housing in place of the old tape. With the cassette casing reassembled, there’s nothing left to do but pair it to a smartphone or other music-playing device and push play on the nearest tape deck.

As smartphones continue to lose their 3.5 mm headphone jacks, builds like this can keep lots of older stereos relevant and usable again, including for those of us still driving older vehicles that have functioning tape decks. Of course, if you’re driving a classic antique auto with a tape technology even older than the compact cassette, there are still a few Bluetooth-enabled options for you as well.

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