No one, to my knowledge, has interfaced a floppy to a PIC/and/ implemented a DOS
file system on it.  I've only heard of people interfacing to floppies, but
haven't seen any actual code or schematics.  Interfacing and controlling the
floppy with the national chip should be fairly easy, the real work comes when
you try to use your PIC to understand the file system on the disk.  I notice you
are trying to make it easier for the PIC by limiting the amount of work it has
to do (create the file, etc) but you will have to create the file somewhere, and
the will likely require a seperate computer and program that understands the
low-level details of the floppy and tailers the file location for you.  However,
file system code is relatively easy to get, you would find such code in the
various free software projects (FreeBSD, Linux, etc).

-Adam

Harold Hallikainen wrote:
>
>         I've got a product using an 18c452 with 128 kbytes of external static
> RAM. I'd like to add low cost removable storage, and the 3.5 inch floppy
> seems ideal. The drives are incredibly cheap, and so is the media. I've
> included a National FDC chip on the board, but have not as yet looked at
> writing any code for it.
>         In this application, I'm looking at saving and loading an ascii text
> file to/from the disk. To keep costs down and operation simple, we have
> no display on the product, so the operator just hits a button to load a
> file from the disk and another button to save it (with some precautions
> to make sure current data in RAM or on disk is not accidentally wiped
> out). I'm thinking of using PC format with a fixed filename, again
> further simplifying it. There would be no way to format a disk, delete
> the file, etc. Just load and store.
>         Has anyone done anything like this? Another approach I'm considering is
> making a very small embedded 80x6 system that is a FD to EIA232
> interface. Then I could use something like DataLight's ROM-DOS and have
> most of the code already written. I did something like this years and
> years ago. There I did a 6802 system and wrote code to talk to a
> Commodore 1541 disk drive. On the 6802 system you could save and load
> applications programs, do a directory of the floppy, format floppies,
> etc. Again, the goal there was to try to not have to write an operating
> system, so I used Commodore's.
>         So... Floppies, anyone?
>
> Harold
>
> FCC Rules Online at http://www.hallikainen.com/FccRules/
>
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