Is emulating a MMC card using an SPI interface or GPIOs feasible?
I have a portable media player with 30GB harddisk that I'm playing around with hacking. Internally it has 2 SPI interfaces, 32 GPIO interfaces (all but but a handfull are free) on the main chip that runs the device, and runs uCLinux for the OS. It would be rather interesting to have the ability to have it serve as a HD to a device that lacks USB host (camera, SL-5500, etc.), but has a MMC slot. There is a device for PSP that emulates a memory stick card and interfaces a harddisk to it, I'd like to do something like that, but for MMC card using devices.