Macintosh HDI-20 Floppy Drive Hacking. Need help!

[roy18]

I recently got hold of a old Macintosh HDI-20 External floppy drive:
It would be great anyone could point me to a document discussing the protocol of data transfer it uses. If that is too crazy, I would really appreciate anyone who could enlighten me about how I can go about controlling at least the motor positions in this drive. Thanks!

[johnwasser]

Here is the pinout which should help:

http://pinouts.ru/Storage/macfloppy2_pinout.shtml

Looks like a pretty raw interface.  I wouldn't be surprised if "PH0" though "PH3" went directly to the coils of the head stepper motor.

[roy18]

@johnwasser: Wow I think you are right! I didn't try it yet but searching "phase0+floppy" got me to this link:
http://www.thesvd.com/svd/apple-dongle.php where it says:
"The head movement mechanism for the Apple is direct drive pulses targeted toward the stepper motor in the floppy hardware. These pulses are labeled phase 0 through phase 3. When the Apple wants to seek the floppy head to another track, it will pulse these phase lines causing the disk stepper motor to advance either "in" or "out" depending upon the previous phase.
For example, if the last pulse was on phase 1, a pulse on phase 2 will step the disk drive head out, whereas a pulse on phase 0 will step the disk drive head in."

Hopefully, I will get it to make some noise once I hook up wires to those pins.
Thanks!