Behind Billy's New Brain

October 20, 2009

4 Min Read
Behind Billy's New Brain

Don’t be ashamed

Go ahead, admit it. In the back of your closet, up on a shelf in the garage, or in a box where it got packed away but never unpacked, lies one of the most popular novelty gifts of the 21st century: Big Mouth Billy Bass. Billy was introduced to the world in April 2000, and was an immediate hit. Many stores sold out inventory in days and had to put customers on waiting lists. By December of that year, however, the fickle novelty shopper had moved on, resulting in a glut of animatronic fish and other creatures on ebay.

Billy undoubtedly brought his owners great pleasure. I can say with certainty that my kids were entranced by it. Unfortunately even his most ardent fans probably grew bored with his limited repertoire. But what if you could teach new songs and dance moves to your Billy Bass? Would that be enough to rescue your imaginative ichthyoid from its dusty repository?

Billy’s new brain
A new ARM based development platform has been released called MBED. With a free online development environment and simple one minute installation (just connect it to a USB port) you can be up and running your first blinky LED program in less than five minutes. When I first got my hands on one I know this could be the bionic brain Billy needed (”We can make him better than he was before. Better, stronger, faster.”)

You can find the technical details (and a video of Billy in action) in a recent edition of “Gadget Freak” here on Design News. To summarize, I opened Billy up and found two PCBs, one larger with the drivers for the mechatronics and the speaker, and one smaller with the brain. A little probing with a scope allowed me to figure out the 10 wire interface between the two. MBED, with its PWM I/O, D/A converters, and digital inputs seemed like a good match to interface with the existing driver circuits. I removed the original Billy brain (it is currently in cryogenic storage in an undisclosed location) and connected the interface instead to an RJ-45 punch down jack that is hot glued to a hole in the back of Billy’s plaque.

A cut up network cable then plugs into the back of Billy and connects him to the MBED. The MBED sits on a wireless breadboard along with a micro-SD card slot. I wrote firmware for MBED to read and play back .wav sound files. The MBED C++ development environment includes class libraries for everything else: Digital I/O, Analog I/O, PWM, even a FAT filesystem for the SDcard using the SPI interface.

The .wav files (and accompanying motion files) are stored on the micro-SD, and the firmware reads and plays them back in turn. I found sound clips from The Simpsons, Office Space, recent political figures, and of course Monty Python. After choreographing the motion files I put Billy through his paces and created a video for Watch it here on Design News.

The comeback tour
Billy made his comeback from pop culture obscurity at ESC Boston, in the NXP booth . He was subsequently featured on gizmodo, hackaday, geeksaresexy,, and Design News, where he has been viewed over 350,000 times. He has not, however, received any marriage proposals (that I am aware of).
But wait, there’s more
For the ESC demo, a colleague and I wanted to show some internet connectivity. An RJ-45 socket was wired to the MBED ethernet interface, and new firmware was written that would poll for twitters sent to Billy. When it found one it would send the text to a server to have it converted into speech, and would then play the resulting .wav file along with some movements that were made up on the fly. The whole thing was video streamed over the internet allowing anyone to send a twitter to Billy and then watch as he spoke what you twittered.

Difficulty level
This project is rated as simple. Only basic soldering skills are needed to modify the Billy Bass PCB. The MBED development environment makes the coding simple, and the wireless breadboard makes it quick and easy to build the circuit. How could it be improved? If I were doing it again I’d completely remove the existing Billy Bass PCB. I’d use my own transistor driver circuits for the motors and an audio amplifier chip for the sound. I’d also put a DC blocker on the D/A output. It’s ground referenced meaning there’s a DC offset in the audio output that causes the speaker to click a lot between audio clips

In closing, let me remind you that the gift giving season is rapidly approaching. What better way to say “Happy Winter Solstice” than by giving your loved one a gift that is both recycled and handmade? A Big Mouth Billy Bass with a custom holiday message could be just the gift for this year.

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