I just bought a SanDisk 1GB Ultra II SD + USB at Staples for about $27.
I have several projects that use SD cards in SPI mode for data storage. This SD card seems to work fine after a limited amount of testing. My logger can read and write to the card in SPI mode. The files it writes can be read when the card is plugged into a USB port on my PC.
Here's the question:
Can I run 4 wires from the USB port on this card and get an almost free High-speed USB port for my data logger? Could it be as simple as not trying to write via the SPI port while the USB port is connected? Heck, I'd even be willing to tri-state the SPI data lines and clock if necessary. The logger uses an AT91Sam7S256, and I can tri-state the SPI port lines if necessary, but I can't now disconnect the +3.3V to the SDI card socket.
I sent this question to SanDisk support---but I don't know if they work weekends. ;-)
I nobody has any clues for me before tomorrow afternoon, the soldering iron comes out. I'll let you know what happens.
Mark Borgerson