hardware and software for electronic music 
Sat, May 24, 2014, 08:47

DIY without audio interface using microcontroller?

Hi, I'm a 3rd year mechatronic engineering student, I also play the piano and I envy violin players for all the variety of expression available to them.
I'm really interested in building this project but I don't have a lot of money for a 8x8 audio interface.
I was wondering if you could suggest a suitable microcontroller with a fast enough sample rate on the A/D converter to get enough information to do a FFT ?
Also, would it be suitable to generate the sine waves from a microcontroller using PWM ?
And the frequency of of sine waves, logically you would have to be near the cutoff frequency of the filter so that when you change the capacitance by pushing the plates together you change the gain of the filter, so what is the tipical capacitance in your 8x8 setup?
I would probably need to amplify the signal when using microcontroller, what strength of signal can I expect Vpp?
This is a very large project.. maybe I should first just build a single squishy capacitor, and see what I can do..

Wed, May 28, 2014, 09:13

Hi there and welcome.

There are so many microcontrollers out there. I don't really have a suggestion. For the Soundplane we designed our own board around a TI DSP. But I did look at the Beaglebone Black the other day for a while. It looks like it has a bunch of power. If I were starting a DIY project I might try using that.

Lots of the other details you mention are addressed in the paper. But that's only one implementation and there are many other ways to do it. typical capacitances are in the 10s of pF. The cutoff frequency is not an issue anywhere, the cap. changes the gain of the circuit equally from 0--DC more or less.

I would definitely start with one squishy capacitor first, and see what you can do.