The Smallest MIDI Synthesizer?

Dang. [Mixtela] has just managed a seriously cool hack: running an entire MIDI synthesizer on an ATTiny85 to create what he claims is the worlds smallest MIDI synthesizer. That’s it on the left, next to a standard MIDI cable plug. microMidi3-guts-thumbThe whole thing is so small it fits inside a MIDI plug and can run off the power supplied by the MIDI output, driving a small pizeo buzzer. Considering that the ATTiny85 has just 8Kb of memory and 512 bytes of RAM, this is no small feat (get it?). To create the sound, [Mixtela] simply drives the buzzer with PWMed square waves, creating the glorious early chiptunes sound that every retro gamer will recognize.

He even decided to implement some MIDI commands beyond just playing notes, including pitch bending, and is considering ways to add polyphony to his small miracle. Sure, it isn’t going to win any awards for sound quality, and without optoisolators it doesn’t really fit the MIDI spec. But it works, and remember that MIDI synthesizers used to be big, expensive devices that required a degree in sound engineering to program. Now, thanks to hackers like [Mixtela], you can build your own from parts that cost only a couple of dollars.

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32C3: 20 Oscillators in 20 Minutes

In terms of implausible stand-up comedy, [Darsha]’s “20 Oscillators in 20 Minutes” is pretty far out there. First of all, she’s sitting down, with googly eyes on her multimeter, and five breadboards and a mess of 9V batteries laid out in front of her. “Has anybody built electronics before? Has anybody built electronics in front of this many people before? Yeah, so you’d better f**king be nice.” And she’s off!

twenty_oscillators-shot0012“Square waves are really good for your speakers.” And a few seconds later, a lub-dub beat-frequency oscillator filled the hall. And then there’s the stand-up clichés: “Anyone in the audience from Norway?!” And “Anyone know what chip I’m using here?” (The 555.) A heckler, or participant, shouts up “What are you doing?” She responds “Building this!” and shows a sketch of the basic layout.

She baits the audience — “Do you want to ask me about duty cycles?” — and tells stories: “And then one time the solder fell in my lap and burned through my crappy jeggings. Who knows what jeggings are? Whooo!!” All the while the clicking gets louder and more complicated.

Then there’s the suspense. “11 minutes left? Shit, I dunno if I’m going to make it this time!” She’s visibly panicked. A question: “How do you protect the outputs from overvoltage?” “I don’t. (pause, laughter) I use some filter caps and just, well, hope that you guys have good insurance.”

Nearing the home stretch, there’s this quasi-rhythmic ticking and pulsing slowly building up in the background. She plugs in another capacitor, and the crowd spontaneously applauds. A little bit later, she shouts “Is it loud enough?” over the din and turns it down. At the end, the timing’s getting really tight, and she calls up someone to help from the audience.

We won’t spoil it, naturally. You’ll just have to watch it run to the end. We laughed, we cried. It was better than Schroedinger’s cats.

(We’d use hex inverters.)

The Hovalin: Open Source 3D Printed Violin Sounds Great

[Matt and Kaitlin Hova] have created The Hovalin, an open source 3D-printed violin. Yes, there have been 3D-printed instruments before, but [The Hovas] have created something revolutionary – a 3D printed acoustic instrument that sounds surprisingly good. The Hovalin is a full size violin created to be printed on a desktop-sized 3D printer. The Hovas mention the Ultimaker 2, Makerbot Replicator 2 (or one of the many clones) as examples. The neck is one piece, while the body is printed in 3 sections. The Hovalin is also open source, released under the Creative Commons Attribution Non-Commercial Share Alike license.

A pure PLA neck would not be stiff enough counter the tension in the strings, so [The Hovas] added two carbon fiber truss rods. A handful of other components such as tuners, and of course strings, also need to be purchased. The total price is slightly higher than a $60 USD starter violin from Amazon, but we’re betting the Hovalin is a better quality instrument than anything that cheap.

The Hovalin was released back in October. There are already some build logs in the wild, such as this one from [Emulsifide]. Like any good engineering project, the Hovalin is a work in progress. [Matt and Kaitlin] have already released version 1.0.1, and version 2.0 is on the horizon. Hearing is believing though, so click past the break to hear [Kaitlin] play her instrument.

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Color Sonification Could Be Key to Rainbow Connection

Have you seen any loud sweaters this holiday season? Now there is a way to quantify their vibrancy and actually hear them at the same time. Cornell engineering students [Mengcheng Qi] and [Ryan Land] focused on the sonification of color and translated the visible spectrum into audible sounds.

They originally planned to use pixel samples from an OV7670 camera module, but weren’t able to extract any useful color data from it. We prefer their Plan B anyway, which was to use CdS photo resistors and the plastic color filters used for photography in red, blue, and green. The varying intensity of light falling on the photo resistors creates different patterns according to the voltage levels. The actual sound generation was done with FM sound synthesis.

There wasn’t a lot of natural sound variation between different RGB values, so in order to make it more fun, they created different instruments which play different patterns at variable speeds and pitch according to the colors. In addition to the audio feedback, the RGB values are displayed in real-time on a small TFT. Below those are dynamic bar graphs that show the voltages of each color.

Check out the demo after the break; they walk through the project and try it out on different things to hear their colors.

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Muscle Wire Pen Dances to Duke Nukem

[serdef] is clearly just having a little bit of fun here. One never needs a whiteboard pen that’s syncronized by MIDI to dance along with the theme from Duke Nukem.

But if you had all of the parts on hand (a highly liquid MIDI-driven relay board that connects straight up to a soundcard, some muscle wire, tape, and a whiteboard pen, naturally) we’re pretty sure that you would. You can watch the dancing pen in a video below the break.

The project is really about documenting the properties of [serdef]’s muscle wire, and he found that it doesn’t really contract enough with a short piece to get the desired effect. So he added more wire. We’ve always meant to get around to playing with muscle wire, and we were surprised by how quickly it reacted to changing the voltage in [serdef]’s second video.

Now the dancing pen isn’t the most sophisticated muscle wire project we’ve ever seen. And that award also doesn’t go to this Nitinol-powered inchworm. Did you know that there’s muscle wire inside Microsoft’s Surface?

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Scratching Vinyl Straddles Physical and Digital Realms

The life of a modern DJ is hard. [Gergely] loves his apps, but the MIDI controller that works with the app feels wrong when he’s scratching, and the best physical interfaces for scratching only work with their dedicated machines. [Gergely]’s blog documents his adventures in building an interface to drive his iPad apps from a physical turntable. But be warned, there’s a lot here and your best bet is to start at the beginning of the blog (scroll down) and work your way up. Or just let us guide you through it.

In one of his earliest posts he lays out his ideal solution: a black box that interprets time-code vinyl records and emulates the MIDI output of the sub-par MIDI controller. Sounds easy, right? [Gergely] gets the MIDI side working fairly early on, because it’s comparatively simple to sniff USB traffic and emulate it. So now he’s got control over the MIDI-driven app, and the hard part of interfacing with the real world began.

After experimenting a lot with timecode vinyl, [Gergely] gives up on that and looks for an easier alternative. He also considers using an optical mouse, but that turns out to be a dead-end as well. Finally, [Gergely] settled on using a Tascam TT-M1, which is basically an optical encoder that sits on top of the record, and that makes the microcontroller’s job a lot easier. You can see the result in the video below the break.

And then in a surprise ending worthy of M. Night (“I see dead people”) Shyamalan  he pulls timecode vinyl out of the grave, builds up a small hardware translator, and gets his original plan working. But we have the feeling that he’s not done yet: he also made a 3D printed optical-mouse holder.

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Touch Piano Hits All the Right Notes

We love a good musical build, and this one is no exception. For their ECE4760 final project, [Wendian Jiang], [Hanchen Jin], and [Lin Wang] of Cornell built the nicest-looking touch piano we’ve seen in a while. It has five 4051 multiplexers that take input from 37 capacitive touch keys fashioned from aluminium foil and copper tape. Thanks to good debounce code, the sounds are clean even though the keyboard is capable of four-note polyphony.

A PIC32 and a Charge Time Measurement Unit (CTMU) module generate a small, steady current that charges up the keys. The PIC scans the pins continuously waiting for touch input. When human capacitance is detected, the value is compared with the base capacitance using the ADC and the sound is generated with the Karplus-Strong algorithm.

The group’s original plans for the project included a TFT screen to show the notes on a staff as they are played. While that would have been awesome, there was just too much going on already to be able to accurately capture the notes as well as their duration. Check it out after the break.

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