Recently, I was privileged to showcase a project I have been intimately involved with for some time, the Analog Shield, at the TI booth at the Bay Area Maker Faire. For those not familiar, Maker Faire is something like a cross between a state fair and a swap meet. People and companies from all walks of life commingle and show off the things they are passionate about, from Leatherworking to 3D printing. TI was there to show off the tools that enable all these amazing projects to come to life.
The Analog Shield is part of a broader project that stems from my advisor, Greg Kovacs, and his vision to shrink an entire electronics lab down to fit on a couple of Arduino Shields. With the proper tools, electronics lab classes can be taught anywhere in the world, even outside the traditional lab setting. The Analog Shield is the first result of this project, using TI components to greatly improve the analog capabilities of a microcontroller platform. On the board are:
- Analog to Digital Converter (ADC)
- 4 Channel, 16 bit 100ks/s SAR ADS8343.
- Digital to Analog Converter (DAC)
- 4 Channel 16 bit 100ks/s DAC8564.
- Variable +/-7.5V Supply TPS61093.
- Fixed +/-5V Supply.
- Area for bread boarding.
Additionally, we created a library that offers interface to the ADC and DAC with a single line of C. The board is now being produced by Digilent, and can be found at http://www.digilentinc.com/analogShield
I’d like to take a moment to thank the wonderful team at TI who have been instrumental in moving this project forward, as well as our launch partner, Digilent, of course, the team here at Stanford who have supported this project from day one.
In order to show off just how useful a good analog toolkit is, we envisioned a handful of demos and set about making them a reality. We thoroughly documented these demos, so hobbyists and students can reconstruct our work. These demos include a function generator, a four-voice midi player, a Lissajous diagram generator, and a spectrum analyzer.
Of all the demos built around the Analog Shield, the spectrum analyzer probably got the most attention. The spectrum analyzer uses an electret microphone and samples audio using the analog shield, then performing an FFT and displaying the output on a touch LCD. It is capable of sampling signals up to 30kHz and displays the results in real time, using no off board processing. The best part of the demo is that it came with a personal story.
When we first built the analyzer in our lab, we discovered a loud tone at 25kHz, well outside the range of human hearing. At first, we were convinced that the tone was a problem with the analyzer or the microphone, but after finding the tone disappeared when the microphone was muffled or when the analyzer was moved into the hallway, we were able to find the source – the lab HVAC system is emitting a tone that we cannot hear, as loud as the output of our test stereo.
Maker Faire was full of interested onlookers, with Saturday including visits from a Chris Gammell of The Amp Hour, and Alasdair Allan of Make Magazine. Dr. Kovacs also brought a group of Stanford students by who were visiting on a university outing. It seems likely that the Analog Shield will feature in more student projects in the near future.
Sunday included video interviews with Hackaday and Make Magazine, and was capped off by a post show ‘bring a hack’ dinner and meet. Cathy Wicks, of the TI University Program took our spectrum analyzer and taped it to a swaddled in TI-red duct tape, making for a fascinating conversation piece that actually showed the conversation.
All in all, the weekend was wild and wonderful experience that allowed us to share some wonderful work that I have been but a small part of, and hopefully begin the process of bringing that product to the world.
