dfitoimd: decoding Intel M2FM floppy flux images (was Re: Intel 432 floppy flux images for decoding)

Chuck Guzis cclist at sydex.com
Mon Aug 8 13:17:10 CDT 2016

On 08/06/2016 04:12 PM, Eric Smith wrote:
> Because the cwtool support for Intel M2FM floppy disk flux images 
> isn't publicly available, I've written a crude Python 3 program for 
> converting such images (in DFI format) to ImageDisk images, and put
> it on github:
> https://github.com/brouhaha/dfitoimd

Interesting, Eric!

I did my cw-MMFM converter in 32-bit C years ago, but then I use my own
format for the cw files (i.e. I don't use cwtools), so it's probably not
a lot of use to folks--but it's fast.  Metadata is important to me and I
pack my cw image files with as much as possible.

I record two revolutions worth of data per track to get *everything* and
also to give an implied second chance at data that the first rev may
have missed.

To date, on Intel and AES MMFM (they're different) disks, I'm batting 100%.

While I can appreciate wanting to do decoding real-time (i.e. reading
and decoding), the cw approach does give you the option of going back
over the data without the need to stress the disk as many times as one
would care.  One can, for example, insert missing transition data where
dropouts may have occurred on the disk.

And accumulating sample data is pretty much child's play nowadays.  I
have a rig with an micro SD card, an STM32 "maple mini" board and a
couple of TTL driver ICs that works a treat.   It probably set me back
less than $10--and it has USB connectivity, though it can't be powered
by the USB port--a 150 ohm terminated floppy drive just pulls too much
current to be safe.


P.S.   On my bucket list, I'm curious if anyone's ever worked out the
internals of the WD9914 data separator chip.

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