NFSound

Teensy 3.2 with Adafruit RFID Shield
Audio buffer circuit
Serial monitor output

Inspiration

Eric wanted a noisemaker, so we built him one!

What it does

It plays sounds generated by single C statements and RFID cards pick which sound plays.

How we built it

For hardware, we used a Teensy 3.2 and an Adafruit PN532 RFID Shield. The Teensy has a built-in 12-bit DAC that we are using for sound output. It feeds a resistor divider to reduce the output to a lower level and a couple capacitors for filtering.

The C statements for generating sound were found on this blog post. Eric spent a lot of time experimenting with different statements using this online tool. He figured out what statements didnt work well together so we could split them up in the code. The code was built off of one of the examples provided with the RFID shield library. It waits for a card to be detected and reads the UID which is unique to each card. No data can be read from cards with encryption because authentication must be done before read access is granted by the controller IC.

Two values are generated for picking sound functions from an array. Each byte of the card's UID is split into two nibbles. One value is generated using the even-numbered nibbles and the other is generated using the odd nibbles. A modulus is done to get the sum in range of our array sizes.

Finally the sound is generated by feeding a counter into the sound functions that were picked and their output is sent to the DAC on the Teensy.

Challenges we ran into

Many sound-generating statements would produce garbage when combined. We also spent a while coming up with a way to pick statements that was based on a card's UID but seemed random for cards with similar UIDs.

Accomplishments that we're proud of

Eric listened to sooooo many sound samples. Literally all of them.

What we learned

Simple statements like (t&t>>8) produce cool, fractal-like patterns.

What's next for wonderhack

Who knows? Maybe building a spectrum analyzer with lots of LEDs.

Built With

Submitted to

Winter WonderHack

Created by

I wrote the majority of the code after Jordan figured out how to get the UIDs from the cards. I also put the hardware together. I set up the git repo with continuous integration through Travis CI.

Nathan Duprey
Worked with the adafruit nfc shield to pull the UID for use in determining what sound components to use

Jordan Gagnon
I researched bit-shifting, music-generating algorithms. I went through several algorithms altering them to change the style of the music. I then listened to many different combinations of them to make sure that they sounded pleasant (i.e. didn't sound like noise or static).

Eric Stefanko

Updates

Nathan Duprey started this project — Feb 25, 2017 05:51 AM EST

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