images are CC BY-NC-SA 3.0
Description: The Open Music Labs Codec Shield gives your Arduino (or Maple) development board access to the all of the audio processing power of the Wolfson WM8731 codec. The WM8731 is a low-power stereo audio codec with stereo 24-bit multi-bit sigma delta ADCs and DACs which are used with oversampling digital interpolation and decimation filters. Thanks to the variable sampling frequency of the codec, even the relatively slow Arduino can grab and alter audio in real-time.
The Codec Shield breaks out all of the useful pins on the WM8731 including the mic, line-in and out, headphone, and midrail bias voltage pin. It also has 1/8" stereo input and headphone out jacks as well as a pair of potentiometers for modulating parameters in your code.
The shield uses SPI to communicate with the WM8731 so it won't work directly with the Arduino Mega, but getting started on an Arduino-UNO style board or LeafLabs Maple is easy! Just download the library and example code, hook up and audio source and start tweaking.
Obviously you don't have much time to execute code between audio samples, so your code will need to stay pretty slim, but the example code gives a great framework for how your code should flow. Open Music Labs claims a performance increase of 4x when running the shield on a Maple (thanks to the higher clock speed).