Interfacing microcontroller with floppy drive?
Chaos Master
microcontroller? I would like to have the microcontroller get a listing of the
files on the floppy drive - and output it on a LCD display. This would be for a
device for quick checking of floppy disk contents - would be useful for me.
What microcontroller I could use?
Where to find technical info about floppy drives?
Any IC's that could be useful to interface to a floppy drive?
Thanks for attention!
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hamilton
The data rate is to hi to sync up with.
check this data sheet to understand why.
http://www.smsc.com/main/catalog/fdc37c78.html
This chip works well, software is sort of easy on a fast 8051.
( Dallas 80c320 ).
Joel Kolstad
> Sorry, This can _not_ be done with just a micro. ( no matter how fast )
I disagree. You give me, oh, a 100MHz or better microcontroller with
nothing else to do and a bunch of built-in I/O, I'll give you a MFM decoder
for regular 1.44MB PC-formatted disks (1Mbps).
This is, of course, a waste of about 95% of the transistors in a
microcontroller... (Then again, those guys at Scenix seem to like this
approach to building peripherals... hmm.... maybe one of those 50MHz Scenix
PIC clones could do this after all!)
---Joel Kolstad
Rene Tschaggelar
Rene
Stef Mientki
hamilton wrote:
> Sorry, This can _not_ be done with just a micro. ( no matter how fast )
Does anyone still use floppies these days ?
At least/last you can always do something like this
http://skool.dyndns.org/~critter/projekt/pictures.html
http://www.ohmslaw.com/robot.htm
http://www.generation5.org/content/2001/floppy.asp
Stef Mientki ;-)
Tim Auton
>hamilton wrote:
>
>> Sorry, This can _not_ be done with just a micro. ( no matter how fast )
>
>Does anyone still use floppies these days ?
Old floppies that have been unused for years are being pressed into
service again thanks to Viagra ;)
Tim
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hamilton
Chaos Master
sci.electronics.design' I found a message from
hamilton[hami...@deminsional.com]:
Hamilton,
> Sorry, This can _not_ be done with just a micro. ( no matter how fast )
>
> The data rate is to hi to sync up with.
>
> check this data sheet to understand why.
>
> http://www.smsc.com/main/catalog/fdc37c78.html
>
> This chip works well, software is sort of easy on a fast 8051.
> ( Dallas 80c320 ).
This is interesting! I will take a look. Thanks!
--
"The transistor is mightier than the tube."
Chaos Master
Mientki[s.mi...@mailbox.kun.nl]:
Stef,
> Does anyone still use floppies these days ?
Yes.
You can't update a PC BIOS from a CD-ROM, AFAIK.
You can make a small Linux-based firewall/router in a 1.44MB floppy, using a 486
with 66MHz clock.
You can have a quick tool for getting to a DOS prompt when Windows gets mangled.
And there are other uses. Be creative!
> At least/last you can always do something like this
--
Paul Hovnanian P.E.
>
> In an arcane spellbook written by the priests, labeled 'Posts of
> sci.electronics.design' I found a message from Stef
> Mientki[s.mi...@mailbox.kun.nl]:
>
> Stef,
>
> > Does anyone still use floppies these days ?
>
> Yes.
> You can't update a PC BIOS from a CD-ROM, AFAIK.
> You can make a small Linux-based firewall/router in a 1.44MB floppy, using a 486
> with 66MHz clock.
> You can have a quick tool for getting to a DOS prompt when Windows gets mangled.
Anyone make a BIOS that will boot off a USB key fob drive yet?
--
Paul Hovnanian mailto:Pa...@Hovnanian.com
note to spammers: a Washington State resident
------------------------------------------------------------------
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-- Adrian Tyvand
Tim Auton
>Chaos Master wrote:
>> In an arcane spellbook written by the priests, labeled 'Posts of
>> sci.electronics.design' I found a message from Stef
>> Mientki[s.mi...@mailbox.kun.nl]:
>>
>>
>> Yes.
>> You can't update a PC BIOS from a CD-ROM, AFAIK.
If the PC can boot from the CD you can stick a copy of DOS and your
flash utility on it just like you can with a floppy.
>> You can make a small Linux-based firewall/router in a 1.44MB floppy, using a 486
>> with 66MHz clock.
>> You can have a quick tool for getting to a DOS prompt when Windows gets mangled.
>
>Anyone make a BIOS that will boot off a USB key fob drive yet?
I seem to recall Dell were looking at making bootable USB key fobs
(for Ford's network initially).
Tim Shoppa
> >Anyone make a BIOS that will boot off a USB key fob drive yet?
>
> I seem to recall Dell were looking at making bootable USB key fobs
> (for Ford's network initially).
Great. Now my key fob can get a virus.
Tim.
Joel Kolstad
> I seem to recall Dell were looking at making bootable USB key fobs
> (for Ford's network initially).
I read an article perhaps a year ago about how the BIOS of PCs was
supposedly going to change in the coming years so as to be (1) written in a
high level language! and (2) more extensible, so that you could easily boot
off of USB flash ROM drives, USB hard drives, etc.
For people setting up (cloning) PCs around the workplace (there are a lot of
these people out there!), the usual approach is still either booting to DOS
with a network 'boot' disk so that something like a Norton Ghost image can
be accessed off of a server (Ghost runs in DOS!), or actually opening up the
PC and connecting a second hard drive temporarily to boot from and create
the image. Being able to boot from a USB 2.0 hard drive instead would be a
boon!
There was some manufacturer... Sun, maybe?, whose plug-in cards had boot
ROMs written in some tokenized language rather than straight assembly,
thereby making them (theoretically) usable on any machine that had the
interpreter for that language. The idea being that initial boot-time
software wasn't performance critical (even if we are talking about, e.g., a
SCSI interface card) and therefore portability concerns won out. Anyone
know the details of this?
I have come across the occasional PCI video card that had a Macintosh/PC
jumper -- just switched an address line on a PROM so that the proper code
was used!
---Joel Kolstad
Joel Kolstad
> Does anybody here knows how to interface a floppy drive (3 1/2") with a
> microcontroller?
Yes. Google is your friend here. A couple years ago I helped a friend
design an MFM decoder to read the data off of a standard 3.5" PC compatible
floppy drive -- the only resources we used were hits in Google, and while it
did take a handful of sites to piece together enough information to fully
understand how it worked, the information is out there. Hint: Add keywords
such as 'pc,' 'ibm,' or 'floppy' to 'mfm decoder' so that you get something
a little more applied rather than just the theoretical backgrounds of MFM.
Next, I'd suggest you go get a PC floppy drive, get its pinout, and just
power the thing up so that it spins continuously. Step the head to the
middle track or so and stick in a formatted PC disk full of data. Watch the
data output of the floppy disk on a logic analyzer or a storage 'scope with
a deep memory, if possible -- this will very quickly allow you to connect
the description of what's going on (what you'll find in those Google hits)
to reality. Come back here if you need to ask stuff like, 'What's all this
pre-emphasis business they're talking about?' (Rest assured you can ignore
it initially...)
Finally, once you understand how the sectors are encoded, get a sector
editor utility for your PC and find a description of, e.g., the FAT file
system (which -- on PCs -- is still used about 99.99% of the time). With
the sector editor, explore the disk's layout until you're confident you
understand what's going on.
Depending on your background and the equpment you have available, all of
this might take you away -- certainly weeks or months of spare time.
> What microcontroller I could use?
Assuming we're still talking PC (FAT format) disks, it takes a
non-negligible amount of code to 'deal' with the file system (although FAT
is about as simple as you can get -- sophisticated file systems meant for
large volumes like NTFS are a nightmare in comparison to FAT!). People have
done the file system decoding in assembly, but it's certainly easier if you
use C and have a microcontroller that has enough memory to make this viable.
(You'll also probably be able to find tested C source code to do the
decoding!) The Atmel atMega's fall into that category, as do some of the TI
MSP430 chips... and I'm sure Microchip has some really big PIC out there
these days, although it left a really sour taste in my mouth some years back
when I started having to deal with PICs requiring you to manually switch
code pages! (This may have been fixed by now...)
> Where to find technical info about floppy drives?
See above.
> Any IC's that could be useful to interface to a floppy drive?
Ah... for the actual floppy disk interface, choose your favorite CPLD. The
data rate, as I recall, is 1Mbps which is slow relative to the speed you can
get out of any CPLD or FPGA these days. A bare bones implementation could
be something like a 32 or 64 macrocell CPLD that's just smart enough to
recognize the sector header and then decode one sector and dump it directly
back to your microcontroller via, e.g., a high speed (1Mbps again) serial
link.
There are inteface ICs out there (the Western Digital 1770/1776 were used in
MANY a computer), but in my opinion using one of those chips forces a whole
system 'architecture' on you I imagine you really don't want (they expect to
interface to standard CPU address/data busses that have some notion of DMA)
as well as limiting how much flexibility you have in being able to decode
different disk formats.
As an example of what you can do, check out this guy's product:
http://www.jschoenfeld.de/products/catweasel_e.htm . See the two square
PLCC chips on the board? You wanna know what's under the sticker? Small
CPLDs! Knowing the designer (Jens Schoenfeld), they're most like Altera
7032's or similar -- Jens is a master at implementing clever designs out of
oh-so-slightly 'obsolete' technology that allows him to build his boards at
prices that hobbyists can afford. Note that -- in the case of his Catweasel
Controller product -- he's using the CPU in the PC (an Amiga) do deal with
the file systems (and possibly even some of the decoding) for the multitude
of disk formats that he supports.
Good luck!
---Joel Kolstad
Joel Kolstad
> Sounds like a marketing opportunity!! Go for it !!! :-)
I'm noticing that Ubicom (formerly Scenix) now has 75MHz PIC-compatible
CPUs, so it would be an interesting challenge. And 4K ROM/262 bytes of RAM
is a little, uh, limited! (But then again, I've been absolutely amazed how
how you can squeeze at least enough of a TCP/IP stack into these tiny
microcontrollers to make something that a Real PC will condescend to talk
to...)
A single chip floppy disk interface that spoke, e.g., serially to another
microcontroller would be a pretty nice little device though. Not anything I
think you'd get rich off of, but it might do pretty well (some of like those
single chip 'USB to RS-232' or 'USB to 8 bit parallel' ICs -- very good
marketing idea, the folks who first thought of that!).
---Joel Kolstad