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PICList Thread
'PIC to Floppy'
1998\01\16@130007 by Gareth McClean

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Let me first apologise if this message appears twice on the list, but it
looks like my previous message has disappeared into thin air.

I'm interested to find anyone who has interfaced a PIC to a standard
floppy drive for data storage. I don't care if the format of the disc is
non-standard. What I am interested in, is if someone has example code to
Read & Write data (here we go on - MFM encoding :-)). My intention is to
produce a low cost, high capacity storage device connected to an I2C bus
(for personal use).

Thanks in advance Gareth

Project & Operations Manager, STB Systems Inc.
Tel: +44 1232 258402, Fax +44 1232 319970, WWW Page: http://www.stb.com

1998\01\16@143734 by Evgeni Nikolov

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part 0 1133 bytes
Well I think that some of questions are disappearing just because nobody has the answer, or because all of the folks are discussing other subjects. I had such an experience these days with a question about I2C FM/IF & PLL receiver (no news no bones - as we say in Bulgaria)

Evgeni

{Original Message removed}

1998\01\16@151744 by davewave

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Gareth:

Seems to me that an off-the-shelf FDD controller chip might be the easiest way
to implement your design. Of course, there will be less expensive ways to
interface a PIC to a floppy drive. Here is an example of a FDD controller IC
from National Semiconductor:

http://www.national.com/pf/PC/PC8477B.html

Good luck with your design.

Dave Sorlien

Evgeni Nikolov wrote:

> Hi Gareth,
>
> Well I think that some of questions are disappearing just because nobody has
the answer, or because all of the folks are discussing other subjects. I had
such an experience these days with a question about I2C FM/IF & PLL receiver
(no news no bones - as we say in Bulgaria)
>
> Evgeni
>
> {Original Message removed}

1998\01\16@153618 by Mikal Hodvik

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Gareth,

I haven't done this, but here's a wild suggestion: Use a plain vanilla PC
floppy disk controller card. They're very cheap. Just work out the interface
from your microcontroller to the card, which should be well-documented in
the PC hacking literature. Seems to me, it would be a huge bonus if the disk
format stays PC-compatible.

Mike Hardwick, for Decade Engineering
In Oregon, Land of Magnificent Stumps
spam_OUTdecadeTakeThisOuTspamworldnet.att.net ~ http://www.decadenet.com


>I'm interested to find anyone who has interfaced a PIC to a standard
>floppy drive for data storage. I don't care if the format of the disc is
>non-standard. What I am interested in, is if someone has example code to
>Read & Write data (here we go on - MFM encoding :-)). My intention is to
>produce a low cost, high capacity storage device connected to an I2C bus
>(for personal use).

1998\01\16@230419 by Mike Keitz

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On Fri, 16 Jan 1998 17:51:53 -0000 Gareth McClean <.....gmccleanKILLspamspam@spam@STBNI.CO.UK>
writes:

>I'm interested to find anyone who has interfaced a PIC to a standard
>floppy drive for data storage.

The major problem is that an entire sector must be written at once.  This
means the controller needs enough RAM or other fast-access memory to
store a whole sector's data (typically 512 bytes) at once or some way to
produce the data on the fly.  No PIC chips have 512 bytes of RAM.  So an
external memory chip of some sort will be needed.

As for hardware, I'd use a PC type floppy controller chip or card, which
goes in one chip from MFM to 8-bit parallel.  Most of these have a couple
of serial ports and a parallel port as bonus.  These chips may buffer a
few bytes, but generally count on the host being able to supply the data
fast enough.

1998\01\18@011232 by Harold M Hallikainen

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OR... you could use a Commodore (commode door?) 1541 drive.  It has a
clocked serial interface (a serialized IEEE488 bus) for the interface.
About 15 years ago I wrote an interface between Microsoft 6800 Basic and
that drive.  There are a few hundred systems still in use.

Harold



On Fri, 16 Jan 1998 16:17:52 -0500 Mike Keitz <mkeitzspamKILLspamJUNO.COM> writes:
{Quote hidden}

1998\01\19@120433 by Gareth McClean

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Mechanically not the neatest of ideas, but better than trying to solder
PLCC devices :-)

Thanks Gareth

Project & Operations Manager, STB Systems Inc.
Tel: +44 1232 258402, Fax +44 1232 319970, WWW Page: http://www.stb.com



       {Original Message removed}


'PIC to Floppy'
1998\03\28@160832 by Oliver Praudisch
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I would like to use a floppy and/or a harddrive for data acquisiton. Does
anyone have any info on tring to do something like that?

Any comments or suggestions would be greatly appreciated.

OP

1998\03\28@165310 by rank A. Vorstenbosch

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Oliver Praudisch wrote:
>
> I would like to use a floppy and/or a harddrive for data acquisiton. Does
> anyone have any info on tring to do something like that?

This comes up now and then on this list.

I doubt that anyone is doing this on a low-end PIC.  The PIC of course would be
fast enough to connect to a floppy disk controller (a 765 or one of the modern
equivalents, or a multi-I/O controller) which only does 500kB/s,
but you'd have problems writing disks that another computer would understand.

In order to be able to read the disks on a PC, you'd have to have a FAT (MSDOS)
file system -- not impossible perhaps, but very difficult because of the simple
reason that the FAT and directory are stored in 512 byte sectors. Changing
these would require reading them, making some changes, and then writing the
sector back.  The current 16Cxx PICs come with up to ~370 bytes of RAM or so,
sadly not enough for a complete sector.  I think there are 17Cxx chips with
over 512 bytes of RAM, though.

If you don't use a file system, but just write data onto the disk as it is
generated then you could probably do it -- keep to the 512 byte sectors so that
you can use the BIOS (or Linux kernel, or whatever Windoze has) to read from
the disk.
If you're prepared to write low-level hardware stuff on a PC, then you can use
different sector sizes, of course.  The 765 has support for sectors of 128
bytes (or even less, with careful reading of the datasheets) and those can be
read by PCs.

The main reason for not using floppies is power consumption, access time and
environmental problems like dust, water, snow, condensation etc. in most
outdoor data-logger-type locations.  Depending on your storage requirements,
you could use serial or parallel EEPROM or SRAM, or even (with addition of
external counters or shift registers to generate all those address lines)
PCMCIA cards.

Frank
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