what do you need measured

[aff-man]

Ahhhh what i am talking about is a usb flash drive. The code i am looking for is the one that is on the micro that when getting the info stores it in a nice "filing system" so when plugged into a comp it can easily be read and recognised.

[jrandom]

Ahhhh what i am talking about is a usb flash drive. The code i am looking for is the one that is on the micro that when getting the info stores it in a nice "filing system" so when plugged into a comp it can easily be read and recognised.

Aha, right. Like one of those key-ring drives, you mean.

Do you have the USB host/master protocol stack implementation sorted, then? That's a pretty heavyweight thing to put on a PIC! In fact I don't know of *any* products that use software USB hosts. You'd really need an external USB host controller slaved off your micro.

And after you've sorted *that* out you'll need a FAT16/32 implementation, which is your 'filing system'. The USB storage devices present a sector-level interface, similar to ATA hard disks and the like, which you need to plug in at the device-driver layer of your filesystem. You're talking a *lot* of code there, DEFINITELY more than you could do yourself as a project, so you'd need to find a GPL'd implementation that you could plug in, etc.

I should really make the point that implementing a USB host to run devices that present the standard USB mass storage interface seems like far too much work for this project of yours. In fact you would do very well to avoid USB altogether, it's a minefield of design-by-committee protocols and nigh on impossible to get working well in an embedded system from scratch.

I strongly suggest you do an SD/MMC card interface instead, that way you still have interoperability with desktop computers, etc, but it'll be an order of magnitude easier to implement. You'll still have to find your FAT16/32 source code though.

[Ghost Lemur]

IIRC - didn't one of the OSS groups release an open source verison of FAT?

I know MS's paitent over FAT is currently being reviewed and should hopefully be voided. Will make things like this a hell of a lot easier to impliment.

[jrandom]

Google for FreeDOS.

Or you could rip the FAT management code out of the relevant modules in the Linux kernel.

Keep in mind the requirements of the relevant open-source/free-as-in-speech licenses - redistribution, copyleft etc.