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'[EE] Floppy drive emulator'
2007\06\14@152021 by Mark Hanchey

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Is anyone aware of a circuit that would allow a SD memory card to be
attached to a pc
in place of a floppy drive so that the host pc thinks its accessing a floppy.

I ask because its getting to be a pain to update bios, install
storage drivers, etc on pc
that require you to use a floppy. You can't use usb or cdrom.

If I could change out the floppy drive with something that read SD
cards that would be great.
Just wondering if someone has already designed a circuit like this,
or if I should start :)

I'm aware of the flashpath adapters but they are pricey and I'm
looking for a more hardware based idea.

Thanks
Mark

2007\06\14@153207 by M. Adam Davis

face picon face
Newer motherboards (the ones I've used) support flashing Bios from
windows or USB memory sticks.

I haven't seen an SD to floppy adaptor other than those you've
mentioned, but I suspect that time and money wise you're better off
getting a real floppy drive and a floppy disk.

-Adam

On 6/14/07, Mark Hanchey <spam_OUTmworksTakeThisOuTspammodworks.net> wrote:
{Quote hidden}

> -

2007\06\14@154112 by Mark Hanchey

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At 03:32 PM 6/14/2007, you wrote:
>Newer motherboards (the ones I've used) support flashing Bios from
>windows or USB memory sticks.
>
>I haven't seen an SD to floppy adaptor other than those you've
>mentioned, but I suspect that time and money wise you're better off
>getting a real floppy drive and a floppy disk.
>
>-Adam

Yeah the problem is I'm working with a lot of older hardware , some
of which doesn't
even support usb.

mark

2007\06\14@160649 by M. Adam Davis

face picon face
I used to do a lot of work with older systems booting to the network
from a floppy drive.  I replaced most of the floppy drives with
compact flash cards and IDE adaptors, but never needed to worry about
bios updates.

Will your motherboards flash from hard drives?  (ie, compactflash in IDE mode)

Good luck in your search!  The floppy drive interface is very low
level.  I imagine a floppy drive could be emulated using a PIC,
though, but good luck digging that up and getting it to work.

If you do, you'll have a nice niche product that I expect would sell
pretty well for several years, if not decades.

-Adam

On 6/14/07, Mark Hanchey <.....mworksKILLspamspam@spam@modworks.net> wrote:
{Quote hidden}

> -

2007\06\14@162506 by Herbert Graf

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On Thu, 2007-06-14 at 15:20 -0400, Mark Hanchey wrote:
> Is anyone aware of a circuit that would allow a SD memory card to be
> attached to a pc
> in place of a floppy drive so that the host pc thinks its accessing a floppy.
>
> I ask because its getting to be a pain to update bios, install
> storage drivers, etc on pc
> that require you to use a floppy. You can't use usb or cdrom.
>
> If I could change out the floppy drive with something that read SD
> cards that would be great.
> Just wondering if someone has already designed a circuit like this,
> or if I should start :)
>
> I'm aware of the flashpath adapters but they are pricey and I'm
> looking for a more hardware based idea.

CF cards are ATA compatible, and with a cheap adapter will plug into an
IDE port of a MB, can't get much cheaper or simpler then that.

TTYL

2007\06\14@171717 by Jeff Findley

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"Herbert Graf" <mailinglist3spamKILLspamfarcite.net> wrote in message
news:1181852704.3695.5.camel@PD804...
> CF cards are ATA compatible, and with a cheap adapter will plug into an
> IDE port of a MB, can't get much cheaper or simpler then that.

That would require a bit of juggling of the HD settings in the Bios on
really old PC's (the ones that don't automatically recognize the parameters
of the drive by querying the drive), but I would think that would work just
fine as long as you know what you're doing.  ;-)

CF cards are getting pretty cheap these days.  The going rate around here is
about $15 for 1GB of CF and about the same for the CF to ATA/IDE adapter.
But then really old PC's won't like large CF cards, so you'd want to use a
256 MB or smaller card for these really old machines.

Jeff
--
   "They that can give up essential liberty to obtain a
    little temporary safety deserve neither liberty nor
    safety"
- B. Franklin, Bartlett's Familiar Quotations (1919)



2007\06\15@051956 by Tamas Rudnai

face picon face
About 6 yrs ago I bought a SmartMedia adaptor like this. It had a socket for
the memory card and you could insert this device into an ordinary floppy
drive so you could read and write your media like that. By that time it was
cool, but nowadays a USB adaptor makes more sense as most recently produced
PCs does not equipped with floppy drive. I'm not even sure if WIndows is
capable of handling other than FAT12 on a floppy drive? Anyway, that floppy
adaptor needed two CR232 batteries as far as I remember which did not last
too long when heavily used.

Tamas


On 6/14/07, Jeff Findley <.....jeff.findleyKILLspamspam.....ugs.com> wrote:
{Quote hidden}

> -

2007\06\15@091540 by Anand Gadiyar

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>
> Good luck in your search!  The floppy drive interface is very low
> level.  I imagine a floppy drive could be emulated using a PIC,
> though, but good luck digging that up and getting it to work.
>
> If you do, you'll have a nice niche product that I expect would sell
> pretty well for several years, if not decades.

  This looks like an interesting thing to try out. Any ideas how one
can go about it? Where do you get the specs for a floppy disc
controller? What possible commands the PC sends to the drive and what
possible responses it needs to give back, and so on.

-Anand

2007\06\15@093144 by M. Adam Davis

face picon face
I'd start with this:

http://www.interfacebus.com/PC_Floppy_Drive_PinOut.html

Assuming all the signals are digital, then it's a pretty
straightforward low-level interface.
There are a few tutorials on how to control the motor and stepper of
the drive.  Beyond that, hook up a drive and play around.  The motor
signals for drive A and B can be found here:
http://www.nullmodem.com/Floppy.htm

-Adam

On 6/15/07, Anand Gadiyar <gadiyarspamspam_OUTgmail.com> wrote:
{Quote hidden}

> -

2007\06\15@093934 by M. Adam Davis

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I don't know how similar the amiga drive is, but my suspicion is that
the basics are all the same, with differences in track and sector
density.

So this should be a gold-mine:
http://www.techtravels.org/amiga/amigablog/

And here is an SD/MMC floppy drive emulator:
http://www.sensi.org/~tnt23/megadrive/index.html

It's for the amiga, though, so you'll have to work through it to see
how similar it really is.

-Adam

On 6/15/07, M. Adam Davis <@spam@stienmanKILLspamspamgmail.com> wrote:
{Quote hidden}

2007\06\15@095850 by Jeff Findley
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"Tamas Rudnai" <RemoveMEtamas.rudnaiTakeThisOuTspamgmail.com> wrote in message
news:spamBeGone492f1420706150219v1da15952ga2c56c172553f93espamBeGonespammail.gmail.com...> > About 6 yrs ago I bought a SmartMedia adaptor like this. It had a socket
> for
> the memory card and you could insert this device into an ordinary floppy
> drive so you could read and write your media like that. By that time it
> was
> cool, but nowadays a USB adaptor makes more sense as most recently
> produced
> PCs does not equipped with floppy drive. I'm not even sure if WIndows is
> capable of handling other than FAT12 on a floppy drive? Anyway, that
> floppy
> adaptor needed two CR232 batteries as far as I remember which did not last
> too long when heavily used.

I didn't remember these things.  Looks like you can still buy them:

http://www.usbflashstore.com/sasmflflad.html

Here's an MMC/SD version (which would seem to be the more popular flash
format today):

http://www.usbflashstore.com/smarsecdigfl.html

The advantage here is you don't have to open the older PC's case to boot
from this.

The downside is that it appears you have to install drivers for these
things...

Jeff
--
   "They that can give up essential liberty to obtain a
    little temporary safety deserve neither liberty nor
    safety"
- B. Franklin, Bartlett's Familiar Quotations (1919)



2007\06\15@110012 by Herbert Graf

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On Fri, 2007-06-15 at 10:19 +0100, Tamas Rudnai wrote:
> About 6 yrs ago I bought a SmartMedia adaptor like this. It had a socket for
> the memory card and you could insert this device into an ordinary floppy
> drive so you could read and write your media like that. By that time it was
> cool, but nowadays a USB adaptor makes more sense as most recently produced
> PCs does not equipped with floppy drive. I'm not even sure if WIndows is
> capable of handling other than FAT12 on a floppy drive? Anyway, that floppy
> adaptor needed two CR232 batteries as far as I remember which did not last
> too long when heavily used.

I remember those! They were pretty cool, and probably were created as a
result of the "floppy drive" digital cameras, people upgrading from
those cameras didn't have a card reader for this new fangled "flash
card" thing, so the floppy adapter was the result.

How times have changed...

2007\06\15@113524 by olin piclist

face picon face
Mark Hanchey wrote:
> Is anyone aware of a circuit that would allow a SD memory card to be
> attached to a pc
> in place of a floppy drive so that the host pc thinks its accessing a
> floppy.

I did something similar for a customer a few years ago.  The board connected
to the floppy cable and looked like a floppy to the system.  A PIC
communicated on the floppy bus and read and wrote to a on board flash that
simulated the bits stored on the floppy.  This particular unit was just a
demonstrator of the capability.  It had a serial interface so that the
simulated floppy data image could be saved and restored externally.

Note that the low level pulses transmitted over the floppy cable are a long
way from a file system.  My device only emulated a raw floppy.  It's
obviously doable to translate between this and files, but not trivial.


********************************************************************
Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
(978) 742-9014.  Gold level PIC consultants since 2000.

2007\06\15@121656 by Peter P.

picon face
Olin Lathrop <olin_piclist <at> embedinc.com> writes:

> I did something similar for a customer a few years ago.  The board connected
> to the floppy cable and looked like a floppy to the system.  A PIC
> communicated on the floppy bus and read and wrote to a on board flash that

May I ask what type of PIC was able to write and read raw clocked bits at 2MHz
or 4MHz bit rate ? I assume that somehwhat extensive hardware was used for this.
I'd be tempted to use a DRAM for this if I'd have to. But I can see how a PIC
could use this. A larger DRAM of say 256kx1 would store 512 sectors (a 1.44 MB
floppy has 2880 of those).

thanks,
Peter P.


2007\06\15@124715 by olin piclist

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Peter P. wrote:
> May I ask what type of PIC was able to write and read raw clocked bits
> at 2MHz or 4MHz bit rate ?

Actually it took 2 PICs, a small 14 bit core device and a 16F877.

> I assume that somehwhat extensive hardware
> was used for this.

Not really, but it did take some cleverness.  If I remember right there was
some hardware to deal with switching between reading and writing, but
otherwise the data line went directly into and out of the PIC.

> I'd be tempted to use a DRAM for this if I'd have
> to.

Why?  The storage requirements are so low, and static RAM makes things
easier.  I had both a static RAM and a flash memory.  The floppy data was
read/written to the static RAM.  Dirty bits were set for blocks of the RAM,
and the PIC would write dirty blocks of RAM to the flash as it could when it
had nothing else to do.  The flash write time was much less than required to
keep up with the floppy data rate.


********************************************************************
Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
(978) 742-9014.  Gold level PIC consultants since 2000.

2007\06\15@131005 by Herbert Graf

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On Fri, 2007-06-15 at 18:45 +0530, Anand Gadiyar wrote:
> >
> > Good luck in your search!  The floppy drive interface is very low
> > level.  I imagine a floppy drive could be emulated using a PIC,
> > though, but good luck digging that up and getting it to work.
> >
> > If you do, you'll have a nice niche product that I expect would sell
> > pretty well for several years, if not decades.
>
>    This looks like an interesting thing to try out. Any ideas how one
> can go about it? Where do you get the specs for a floppy disc
> controller? What possible commands the PC sends to the drive and what
> possible responses it needs to give back, and so on.

Well, that right there is the problem. Floppy drives are VERY "dumb".
They don't have any sort of "controller" on board, all the smarts are on
the MB.

The interface itself is VERY raw, something like "move motor one step
forward", "feed me the raw bits from the disk", stuff like that.

TTYL

2007\06\15@184430 by Dave Tweed

face
flavicon
face
Peter P. wrote:
> May I ask what type of PIC was able to write and read raw clocked bits
> at 2MHz or 4MHz bit rate ?

????

What kind of floppies do you have?

All the standard ones I'm aware of run at 250 or 500 kbps, including the
ubiquitous 3.5" 1.44 MB size. There were some very early 5.25" and 3.5"
drives that ran at 125 kbps.

-- Dave Tweed

2007\06\16@062424 by Peter P.

picon face
Dave Tweed <pic <at> dtweed.com> writes:
> > May I ask what type of PIC was able to write and read raw clocked bits
> > at 2MHz or 4MHz bit rate ?
> What kind of floppies do you have?
> All the standard ones I'm aware of run at 250 or 500 kbps, including the
> ubiquitous 3.5" 1.44 MB size. There were some very early 5.25" and 3.5"
> drives that ran at 125 kbps.

I think that I confused the data recovery PLL clock with the bit rate. Anyway I
was thinking about a DRAM because it is 1 bit wide. I suppose that one could try
to use a MC/SD card or directly NAND flash in a similar way instead (don't know
about write speed). My interest lies esp. in making a gizmo that can appear as a
bootable 1.44MB floppy to a motherboard through a standard floppy connector.
Write is not necessary, and capacity need not be a full 1.44MB. This would be for
the plethora of boards that refuse to bot reliably from USB sticks.

Even at 500kHz data must move 'into' the PIC every 2usec. This is fairly fast
esp. if it needs to be de-serialized (not necessarily 8 bits wide - I do not
remember the width of sector marks and start sequences on floppies) and then
written into SRAM.

thanks for the answers,
Peter P.



2007\06\16@090145 by enkitec

picon face
On 16 Jun 2007 at 10:23, Peter P. wrote:

> Even at 500kHz data must move 'into' the PIC every 2usec. This is fairly fast
> esp. if it needs to be de-serialized (not necessarily 8 bits wide - I do not
> remember the width of sector marks and start sequences on floppies) and then
> written into SRAM.
>

       Use an Atmel AVR running at 20MHz.
       It can execute almost 40 instructions in 2uS.

       Mark Jordan

2007\06\16@195710 by olin piclist

face picon face
> On 16 Jun 2007 at 10:23, Peter P. wrote:
>
>> Even at 500kHz data must move 'into' the PIC every 2usec. This is
>> fairly fast esp. if it needs to be de-serialized (not necessarily 8
>> bits wide - I do not remember the width of sector marks and start
>> sequences on floppies) and then written into SRAM.

I didn't see Peter's original post for some reason, but as I said I did this
with two PICs.  The first was the smallest 14 bit core PIC available at the
time, which I think was the 16F627.  The operating loop for this PIC was
under 20 instructions long.  Today I could use a 12F629 (I think that's the
current smallest 14 bit core part) for the first PIC if keeping with the
same overall architecture.  The second PIC was a 16F877, and was the main
controller.

The bit rate is 500KHz, but there is only 1uS (5 instructions) between edges
often.  The 14 bit core (as apposed to the 12 bit core) was essential for
the first PIC.


********************************************************************
Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
(978) 742-9014.  Gold level PIC consultants since 2000.

2007\06\16@201058 by David VanHorn

picon face
On 6/16/07, TakeThisOuTenkitecEraseMEspamspam_OUTgmail.com <RemoveMEenkitecspamTakeThisOuTgmail.com> wrote:
> On 16 Jun 2007 at 10:23, Peter P. wrote:
>
> > Even at 500kHz data must move 'into' the PIC every 2usec. This is fairly fast
> > esp. if it needs to be de-serialized (not necessarily 8 bits wide - I do not
> > remember the width of sector marks and start sequences on floppies) and then
> > written into SRAM.
> >
>
>         Use an Atmel AVR running at 20MHz.
>         It can execute almost 40 instructions in 2uS.

And has SPI hardware that runs fast!

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