PIC18F2550(USB) + SDCARD + FAT + WINDOWS

pasini · Joined: 12 Dec 2005 Posts: 50 Location: Curitiba - Brazil

MPLAB 7.1 CCS 3.235

Hi all,
I have a PIC18F2550 connected to an SDCARD by the SPI interface. I want to connect the SDCARD to the PC to be used as a PEN-DRIVE, USB interface.
How can I do this ? I can implement FAT12/16 or 32 to the SDCARD, but how do I translate data from the card to the PC ? How will I receive data fromthe USB/PC and read/write it to the files in the card ?
I have some experience with USB as a serial interface but not as a memory.
Any help, advice or example codes are wellcome.
Thanks in advance,
Pasini

Ttelmah · Guest

If at the PC end, you are going to use an existing USB interface to a 'Pen drive', as a 'mass storage' device, then the PC, will already be handling FAT. If you want the PC to access the device as sequential 'memory', then you will need to think again about what USB device you implement. If the SDCARD, does not ever need to be readable by a PC directly, and you want to modify the data from the PIC, as well as handling the 'pass through', then you would find it much simpler, to interface a bulk I/O device, and write to the card using your own format, rather than FAT.

Best Wishes

pasini · Joined: 12 Dec 2005 Posts: 50 Location: Curitiba - Brazil

Actually, the SDCard memory will be a pen-drive. PIC MCU will not need to read/write any other kind of data.
My project has a RS232-to-USB serial interface in one USB logic channel, working as an Communication Device Class. Ok, this is working.
The other part is the SDCard memory that will be a pen-drive. in this case, I need a FAT-12/16 or 32, ok ? But how do I receive data from the computer, and how do I read/write to the memory ? The card is in SPI mode.
Thanks
Pasini

dmendesf · Joined: 31 Dec 2005 Posts: 31

You need this book:

http://www.powells.com/cgi-bin/biblio?inkey=61-1931448043-0

USB Mass Storage: Designing and Programming Devices and Embedded Hosts by Jan Axelson

sjbaxter · Joined: 26 Jan 2006 Posts: 141 Location: Cheshire, UK

Have a read of Microchips Application Note:

USB Mass Storage Device

it should give you some ideas.

The schematics and sources are all available if you hunt around on the Microchip site.
_________________
Regards,
Simon.

ratgod · Joined: 27 Jan 2006 Posts: 69 Location: Manchester, England

Out of curiosity, has anyone got a version up and running yet?