Paul:
I have worked extensively with floppy drives of all flavors from 8 inch ones all the way down to 3.5 inch units.

My word......do not even think of trying to operate a floppy without a controller. You may want to look into how the original Apple II computer floppy disk controller worked. This used intensive software control with a few simple chips, that among other things, converted byte wide transfers at the processor to serial flow at the diskette drive interface.

The reasons I suggest that a controller is in order have to do with the following items...

1) A software controlled interface would need to have very tight (no latency or jitter) controlled timing to produce consistent flux reversal recording on the floppy drive.

2) Readback of the information off the floppy disk drive actually requires some type of frequency tracking design. Controllers use a PLL for this. But floppy disk drive data recovery is actually a more difficult job than most people these days appreciate. The controller designs of today being complete integrated solutions hide most of what old time floppy disk controller designers like me used to deal with.

3) If you devise a proprietary format for recording on a floppy disk, assuming you overcome quite a number of hurdles getting there, you will sooner or later wish you had PC interchange compatibility. <Trust me...I have been there many times>.

If I were you I would devise instead an interface on your projects for a Compact Flash card. Hooking up one of these things to a microcontroller is rather simple and there is a wealth of idea information sites about doing this on the internet. They operate from the same Vcc (either 3V or 5V) as your microcontroller. Even the smallest Compact Flash cards at 8MB or 16MB will hold scads more data that a floppy diskette.

Michael Karas