9 Feb
2009
9 Feb
'09
3:09 p.m.
Mr Ian Primus wrote:
With today's modern machining technology, it
should definitely be possible
to create a system to write new alignment disks. Starting with a standard
floppy drive, you could replace the stepper drive with something more
precise and controllable.
Like?
A voice-coil actuator /might/ be more accurate than a stepper, but you still
need a servo system to align it. Ladies and gentlemen, meet catch-22: you want
to write the servo tracks, but you need the servo tracks to write the servo
tracks...
Is there a document out there that describes the
track
layout of a standard (say, 5 1/4" 48tpi, 40 track) diskette? There has to
be a spec, one that describes exactly the distance between tracks, the
width of a track, and the distance from the center hub to the beginning of
the first track. If you had that information, and precision measurement
tools, one could set up and calibrate the drive to spec.
<VBG>
8-inch formats: ECMA-58, 59 and 69
5.25-inch formats: ECMA-66, 70, 78 and 99
3.5-inch formats: ECMA-100, 125 and
The FAT filesystem is also standardised -- ECMA-107
All of these wonderful documents are downloadable completely free of charge
from <http://www.ecma-international.org/>
Then, of course, there needs to be a controller for
the thing, a computer
interface to control the precise positioning of the head, as well as being
able to read/write to the disk.
I forget, are we fans of open-source hardware here? As in, circuit diagrams,
firmware, microcode, and operating software / APIs?
My USB disc analyser is "on the bench" and the prototype is talking to the PC
quite happily. Still working on getting the PIC and FPGA to talk, though. The
readback HDL code and RAM interface are proven working and pass the timing
simulations and testbench, but there's a slight difference between "works in
the simulator" and "works on the PCB".
The plan (at the moment) is to release the design, firmware and microcode some
time in July or August. This is slightly complicated by the fact that my
final-year BSc project just happens to be... "A hardware and software solution
for recovering data from obsolete flexible disk formats"
The software is "interesting". I've got a soft-PLL which seems to work quite
nicely (it tracks the drive speed on a bit-by-bit basis, and stores the
decoded bit *and* the deviation from normal).
Of course, I may well need a drive that's having speed regulation issues in
order to prove that it can track the speed correctly...
--
Phil.
classiccmp at philpem.me.uk
http://www.philpem.me.uk/