FRDM boards are great. However they follow Arduino layout and IO oriented. Maybe we should have some fun on it.
I found I2S port is available on FRDM-KL26Z and FRDM-K20. So I will like to propose to design an audio shield for them.
I2S output (interface to low cost UDA1330 DAC)
on board amplifier for headphone or small loudspeaker.
FRDM will use SPI to microSD card, use I2S as output
Arduino and Maple will use multiplex SPI as I2S, so microSD card is useless.
Basically it works a playback device only.
USB host for MSD
I2S input (interface to UDA1341 codec, a legacy silicon since MiniDisk age)
on board amps for headphone and microphone
I want to know your feedback on this idea. The poll is https://community.freescale.com/polls/1184
With reference documents, It can playback wav file with simple driver, acts as USB sound card.
Codec is much useful in digital audio, with proper firmware, it can work as a guitar mixer box, it requires more DSP processing power although.
However it will take more efforts for a complete MP3 decoding. So community co-operation and open source is important.