How much storage do you need WilliamK?
I've started working on a shield, I guess, with 8 FRAM chips.
3.3V parts 877-FM25H20-G
2V parts 877-FM25V20-G
Both are 256K x 8 with SPI interface
x 16 parts are available too, but parallel interface,
128K x 16 877-FM21L16-60-TG
256K x 16, 512K x 16 also available but only in 48 pin BGA. I suppose have someone solder that onto a breakout board.
Anyway, 1M x 16 would give 23 seconds of playback. Hardly seems worth it for audio use for what it would cost
2M x 16 SRAM, loses the battery-less storage capability would provide 46 seconds of storage, could do 2 for stereo, or go for 92 seconds of sound instead.http://www.cypress.com/?docID=33311
Need 21 address lines, 16 data lines, 3 control lines, 1 more for high byte/low byte selection for programming from 8 bit interface.
For audio playback, 3 SPI transfers to load up a start address, then do continuous dummy reads for as long as the sound lasts to increment the address, load the 16 bit data into the DAC, at the 44.1 Hz rate. Use the rising edge of the CS or Output enable to clock the data into the DAC.
Concept seems simple in my head, am sure will be some gotcha's as the design is worked out.
Alternately, use SD card with data going into FIFOs in 512 byte chunks, refresh the FIFO as it runs low, have separate DAC clock circuit to control FIFO address incrementing. FIFOs are expensive and I think hard to come by tho (or were last time I bought some anyway).