I think you just need to mux the IO signals to the SD card. See Page 11 of the datasheet. Insert some hardware between the VUB300 and the SD socket, and between the '328P SPI/SS signals and the SD socket, and decide which set of signals get control of the SD card.74HC125 would do it - need 2 for the VUB300 since it access the card with 4-bit interface. Need 1 for the SPI interface (SCK, MISO, MOSI, SS) since it uses serial interface.Then just need a means to decide who gets control.Maybe have '328 monitor the CLK pin, allow the switch over only when it does not see activity.328 can't drive USB stick without a host shield, something with MAX3241E on it. Sparkfun makes such a shield. I designed one into a card, I didn't do the software behind it, don't know how it turned out.
What I'd like to do in my project, is replace the microSD card with a USB stick
What I'd like to do in my project, is replace the microSD card with a USB stick, OR being able to connect that same microSD card to a PC to put new files on it (without having to physically remove the card from the player).
Very difficult. The SD card has a very simple SPI interface, USB is complicated.
Why can you physically remove the USB stick but not the SD card? That's not fair!
That sparkfun card is not arduino at all, it just has inputs that coud be arduino controlled to select a track.
I think you could use my concept tho, pull the SD/uSD signals off the card, and mux between the PC accessing the SD/uSD card, and the sparkfun board accessing the card. Put a toggle switch on and manually select who gets the card.
QuoteVery difficult. The SD card has a very simple SPI interface, USB is complicated.Well, in Sparkfun's product, the SD card doesn't use the SPI interface. It uses a SDIO interface instead, as SPI wouldn't be fast enough.
The two things aren't interchangeable just because they both store data and they both use flash memory.
QuoteThe two things aren't interchangeable just because they both store data and they both use flash memory.I thought the VUB300 was designed to do just that
The sparkfun board is not a USB Host controller and can't be made to be, so let's just drop the USB stick idea from the discussion going forward if you are planning to use that board.
need 2 for the VUB300 since it access the card with 4-bit interface. Need 1 for the SPI interface (SCK, MISO, MOSI, SS) since it uses serial interface.