Cetacea Prototype One
Last updated: Oct 29, 2019
What Is It?
Cetacea is a collection of four low-frequency oscillators for use in a eurorack modular synthesizer. The module downloads tidal data from the Intergovernmental Oceanographic Commission and plays it back as a control voltage in real time, with a lag of around fifteen minutes. The user can also select a position along the timeline or a speed to progress along it through the use of a potentiometer or a minijack input. At the bottom of the module, the user can mix the four LFOs using Latitude and Longitude inputs and the relative positions of the stations collecting tidal data.
What Is It Now?
I started with the Adafruit Feather HUZZAH ESP8266 for its onboard Wifi. I can collect data when I need and deserialize it on the Feather, but it has too few options for analog input and output. To turn the data into an audio signal I’m using the Teensy, which has a much more robust audio library and is designed to be used in sound/music applications. I’ve been working on figuring out DSP/Wavetable synthesis, but I think if I can send the interpolated voltages fast enough that’s probably better or effectively the same thing anyway.
Ins and Outs
The heart of the module is the interface for addressing the tidal tables. Each of the four tables is addressed with an input jack and a potentiometer, and the result comes from an output jack. Then I have two jacks and two potentiometers for mixing and one final output jack.
I think rather than using the whole Feather board via I2C that the right choice here (for production and for my own convenience) is to use the ESP8266 directly. I have most (if not all) of the board-mount macro hardware already. I am running into some issues with DACs and OPAMPs being mostly surface mount, and small enough that even perfboarding with them isn’t likely to work. I think I’m going to base my work on schematics for RadioMusic and Ornament and Crime, two Teensy-based eurorack modules, and hope those circuits are close to what I want.
My immediate next plan is to lay out a board in Eagle and purchase a DAC8565 for 4-channel DAC audio from the Teensy. I’m relying on the schematics IU mentioned above and making the jump to hardware in order to test using a more complicated circuit as a starting point.