24 May
2023
24 May
'23
9:26 a.m.
On Wed, May 17, 2023 at 5:29 AM Fred Cisin via cctalk
<cctalk(a)classiccmp.org> wrote:
Last time that I tried to research it, I found that
there had once been an
external drive in which the USB and controller werenot integrated with the
drive electronics, so that it could easily get a different drive
connected. It is, of course, not available anywhere.
I also saw a datasheet for a chip that was a USB floppy controller! It
also does not seem to be available.
I have looked in my collection and found 2 external floppy drives with
USB interfaces. Both, not surprisingly, are single 3.5" 1.4M units
One contains a USB floppy drive. That is, after removing the plastic
casing there's a disk drive inside only. The USB cable disappears into
that. After removfn the top shielding cover from that, there's a tiny
PCB with an ASIC on it. USB goes to that, so do the head connections.
So all in one chip, probably not hackable
The other drive is more interesting. There's a drive mechanism and a
little PCB hung off the back. These are connected by a tapewire type
of ribbon cable, I suspect (but have NOT done any tests yet, so this
is a guess) that this is the interface used on some later laptop
floppy drives -- that is much the same signals as on a Shugart floppy
interface. The little PCB has the USB cable soldered to it. And 2 ICs.
Alas some spoilsport has removed the numbers from them. One (14 pins)
is probably a TTL buffer to drive the disk drive signals. The other
(still an SMD dual-in-line package but closer pin pitch than the SOIC
of the other chip) is presumably a USB floppy controller. When I have
time I'll probe things and see if I can figure it out.
-tony