8-Bit Chip Rocks 16-Bit 44.1kHz Tunes

There’s a special place in our hearts for chip tunes generated with your favorite microcontroller. But why stop there? Full-featured audio is a great challenge and it’s not often we see examples of this caliber. It puts out CD-quality audio using not much more than a microcontroller.

How do you get 16-bit audio out of an 8-bit microcontroller. We’ll give you a hint: two pins are used. Not helping? Here it comes: two 8-bit DACs PWM outputs are used on this chip, the ATmega1284. One is used for the lower eight bits, the other handles the upper. The two are combined using carefully calculated precision resistor values and the results are beyond what you imagine. This is produced at a bitrate of 44077.135, slightly off from the 44100Hz standard but we challenge you audiophiles to tell the difference. The wave files are served from an SD card read by the chip using the Petit-FatFs library.

There are so many great things about this project. First off, following [Wancheng Zhou’s] example will let anyone with even basic microcontroller skills build a digital audio player for an [Andrew Jackson] and a couple of [Washingtons]. Secondly, those with a medium uC skill level will want to take the idea and implement/debug it for themselves. Bringing it home, [Wancheng] shows how to gauge the quality of the audio output using FFT.

If you didn’t figure it out by the time of year, this is yet another example of a Cornell ECE 4760 final project. Shout out to [Bruce Land] for inspiring awesome projects and requiring extensive documentation of the projects which itself promotes deeper understand all around.

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World’s First Smart Snowboard Changes Music According To Your Actions

Ever wanted a soundtrack to your life? For a couple of minutes at a time, Signal Snowboards creates that experience with a smart snowboard that varies your music depending on the tricks you perform on your way down the mountain.

The sign on the door says “School For Gifted Hackers”. Inside [Matt Davis] helped interface audio with an accelerometer – something he regularly does with all manner of hacked devices. At first the prototype was an iPhone mimicking the motions of a snowboarder the way fighter pilots describe dogfights with their hands. The audio engine that pulls those mostions to sound is open source and anyone is welcome to do their own tuning.

Once the audio was figured out the boys took it back to their shop and embedded the sensors into a new snowboard. The board is equipped with GPS, an accelerometer, a few rows of LEDs and a bluetooth board to connect to the phone app. It’s all powered by an on-board LiPo battery and a barrel jack out the side to charge it. Channels were cut by hand with a router then electronics sealed in place with epoxy. Not wanting to “just strap some Christmas lights onto a snowboard” the lighting is also connected to the sensors and is programmable.

See the video below of them making the board and taking it out for a test run on Bear Mountain.

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$15 Car Stereo Bluetooth Upgrade

We’ve seen all sorts of ways to implement Bluetooth connectivity on your car stereo, but [Tony’s] hack may be the cheapest and easiest way yet. The above-featured Bluetooth receiver is a measly $15 over at Amazon (actually $7.50 today—it’s Cyber Monday after all) and couldn’t be any more hacker-friendly. It features a headphone jack for plugging into your car’s AUX port and is powered via USB.

[Tony] didn’t want the receiver clunking around in the console, though, so he cracked it open and went about integrating it directly by soldering the appropriate USB pins to 5V and GND on the stereo. There was just one catch: the stereo had no AUX input. [Tony] needed to rig his own, so he hijacked the CD player’s left and right audio channels (read about it in his other post), which he then soldered to the audio output of the Bluetooth device. After shoving all the bits back into the dashboard, [Tony] just needed to fool his stereo into thinking a CD was playing, so he burned a disc with 10 hours of silence to spin while the tunes play wirelessly. Nice!

Speaker Cabinet Boom Box Build

When you get that itch to build something, it’s difficult to stop unless you achieve a feeling of accomplishment. And that’s how it was with [Rohit’s] boombox build.

He started out with a failing stereo. He figured he could build a replacement himself that played digital media but his attempts at mating microcontrollers and SD cards was thwarted. His backup plan was to hit DX for a cheap player and he was not disappointed. The faceplate he found has slots for USB and SD card, 7-segment displays for feedback, and both buttons and a remote for control. But this little player is meant to feed an amplifier. Why buy one when you can build one?

[Rohit] chose ST Micro’s little AMP called the TDA2030 in a Pentawatt package (this name for a zig-zag in-line package is new to us). We couldn’t find stocked chips from the usual suspects but there are distributors with singles in the $3.50-5 range. [Rohit] tried running it without a heat sink and it gets hot fast! If anyone has opinions on this choice of chip (or alternatives) we’d love to hear them.

But we digress. With an amp taken care of he moved onto sourcing speakers. A bit of repair work on an upright set got them working again. The bulky speaker box has more than enough room for the amp and front-end, both of which are pretty tiny. The result is a standalone music player that he can be proud of having hacked it together himself.

‘Nutclough’ Circuit Board Design is Stylishly Amplified

Though there is nothing wrong with the raw functionality of a plain rectangular PCB, boards that work an edge of aesthetic flare into their layout leave a lasting impression on those who see them. This is the philosophy of circuit artist [Saar Drimer] of Boldport, and the reason why he was commissioned by Calrec Audio to create the look for their anniversary edition amplifier kit. We’ve seen project’s by [Saar] before and this ‘Nutclough18’ amplifier is another great example of his artistic handy work.

nutclough2For the special occasion of their 50th anniversary, Calrec Audio contacted [Saar] requesting he create something a bit more enticing than their standard rectangular design from previous years. With their schematic as a starting point, [Saar] used cardboard to mock-up a few of his ideas in order to get a feel for the placement of the components. Several renditions later, [Saar] decided to implement the exact proportions of the company’s iconic Apollo desk into the heart of the design as an added nod back to the company itself. In the negative space between the lines of the Apollo desk there is a small perforated piece depicting the mill where the Calrec offices are located. The image of the mill makes use of different combinations of copper, silk and solder mask either absent or present to create shading and depth as the light passes through the board. This small piece that would have otherwise been removed as scrap can be snapped off from the body of the PCB and used as a commemorative keychain.

With the battery and speaker mounted behind the completed circuit board, [Saar’s] design succeeds in being a unique memento with a stylish appeal. There is a complete case study with detailed documentation on the Nutclough from cardboard to product on the Boldport website. Here you can also see some other examples of their gorgeous circuit art, or checkout their opensource software to help in designing your own alternative PCBs.

Protocol Snooping Digital Audio

More and more clubs are going digital. When you go out to hear a band, they’re plugging into an ADC (analog-to-digital converter) box on stage, and the digitized audio data is transmitted to the mixing console over Ethernet. This saves the venue having to run many audio cables over long distances, but it’s a lot harder to hack on. So [Michael] trained popular network analysis tools on his ProCo Momentum gear to see just what the data looks like.

[Michael]’s writeup of the process is a little sparse, but he name-drops all the components you’d need to get the job done. First, he simply looks at the raw data using Wireshark. Once he figured out how the eight channels were split up, he used the command-line version (tshark) and a standard Unix command-line tool (cut) to pull the data apart. Now he’s got a text representation for eight channels of audio data.

Using xxd to convert the data from text to binary, he then played it using sox to see what it sounded like. No dice, yet. After a bit more trial and error, he realized that the data was unsigned, big-endian integers.  He tried again, and everything sounded good. Success!

While this is not a complete reverse-engineering tutorial like this one, we think that it hits the high points: using a bunch of the right tools and some good hunches to figure out an obscure protocol.

Teensys and Old Synth Chips, Together At Last

The ancient computers of yesteryear had hardware that’s hard to conceive of today; who would want a synthesizer on a chip when every computer made in the last 15 years has enough horsepower to synthesize sounds in software and output everything with CD quality audio? [Brian Peters] loves these old synth chips and decided to make them all work with a modern microcontroller.

Every major sound chip from the 80s is included in this roundup. The Commodore SID is there with a chip that includes working filters. The SN76489, the sound chip from the TI99 and BBC Micro are there, as is the TIA from the Atari consoles. Also featured is the Atari POKEY, found in the 8-bit Atari computers. The POKEY isn’t as popular as the SID, but it should be.

[Brian] connected all these chips up with Teensy 2.0 microcontrollers, and with the right software, was able to control these via MIDI. It’s a great way to listen to chiptunes the way they’re meant to be heard. You can check out some sound samples in the videos below.

Thanks [Wybren] for the tip.

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