Replace SD card board with new Audio/File Storage Subsystem

We intend to start on a new SD/MMC card audio board

This idea involves replacing the current SD/MMCcard/RTC board with an 
RTC/Audio/MMC board. (No longer SD, for the space savings.)

The new audio board would probably drop the I2C bus, in favour of a single 
two-way SPI bus for communicating both date/time and file read/write data. The 
SPI bus would no longer have direct access to the MMC card, since that will be 
'hogged' by the audio playback system. Instead, we'll need to communicate over 
a custom protocol with an onboard ATxmega chip, in order to set/get date/time, 
to command audio file playback and to read and write files.

The xmega chip will run at 3.3V native, as is supplied on the existing SD card 
connector.

Beyond that, nothing more is known or planned at this time.

Meanwhile, the sooner priority of getting the SOMO-14D audio module interfaced 
and working will remain in place -- mostly because Bertrand is already on this 
track and I see no need to pull the plug on it, since this whole new board will 
take a long time to produce.

Oh and by the way -- we looked high and low for an off-the-shelf solution for a 
board like this. Nothing found. Gruvin did find a USB data version for about 
USD$50 -- but it's too big and, well, we want to use MMC, not USB data sticks. 

We also found this one: ... damn. Lost the link. But it's not open source and 
costs way too much -- USD$99+shipping. The size is the biggest limiting factor. 
I think it's much more powerful than we require. For example. we don't need 
MP3. Uncompressed audio is fine.

If anyone knows of a small MMC card, audio playback device with SPI or serial 
file storage and RTC onboard as well -- especially if its open sourced -- then 
please do let us know.

Original issue reported on code.google.com by gru...@gmail.com on 7 Nov 2011 at 3:07

suprimex / gruvin9x

Replace SD card board with new Audio/File Storage Subsystem #67