File I/O with a PIC

[mihids]

How can I read/write a file(FAT32) from a PEN drive using a PIC with a USB interface. Are there any libraries to do this?
Any help would be appreciated!!

 

[Nigel Goodwin]

Very, very, difficult - as you need USB master, and PIC's are USB slave.

Much easier to use an SD card instead of a USB one.

 

[kchriste]

You can get PICs with a USB host interface:
USB Framework for PIC18, PIC24 & PIC32
Quote from above page:

[SIZE=-1]The 8-bit PIC18 family supports USB device mode. The 16-bit PIC24F and 32-bit PIC32 products with USB support device mode, as well as embedded host and On-The-Go. All product families support up to (FS-USB) full-speed operation (12 Mbps).[/SIZE]

 

[mihids]

I've found this!

AN1045 - File I/O Functions Using Microchip's Memory Disk Drive File System Library - Application Notes - Details

But I'm not sure where to begin as I am not a guru in using micro-controllers

Can anyone explain to me where to start? I just want to somehow read a SMALL file stored in a PEN to the PIC.

Thanx in advance!

 

[Sceadwian]

The first thing you need to deal with is connecting to the USB thumb drive, so following up on Kchristies link above would be a good place to start, once you can actually connect the storage device to the pic and access it then you can worry about the file system. You'll either need libraries to access the FAT system on the drive, or if you want to do it the easy way and you can make sure the file is in a specific spot you can use a fixed offset to read the file.
Ordinarily you need to read the file allocation table to determine where a file is where it's parts are and where the offsets for each of those parts are, but if you place the file on the thumb drive using a PC defragment the drive and then use a hex editor to determine the drive offset of the file you need you can put a fixed offset for reading from the PIC, but you have to be very careful you never modify the file on a PC to the point where it would change it's drive offset location.

 

[Oznog]

Many people have written to the interface of SD-RAM cards. It's actually fairly easy, I've not done it but I heard they have a SPI interface that the PIC easily interfaces with. Check the voltage, I think it requires a 3.3v interface.

That SD card can plug into a USB adapter that you can plug into a computer. This may make your project 10x simpler.

 

[Pommie]

Anyone that has to ask on a forum like this, how to host USB, is doomed to failure. Sorry.

Mike.