GreaseWeazle V4 Board designed by Kier Fraser and board by George Rudolf Mezzomo

"Design Title     Greaseweazle v4 - QFP48

Author        George Rudolf Mezzomo

Document Number    01

Revision       1.0

Design Created    10 February 2020

Design Last Modified 28 April 2021

Total Parts In Design 39"

GreaseWeazle V4 USB Floppy Adapter is a Flux Reader/Writer for Amiga, Atari, PC, Amstrad, PDP-11 and many more vintage computer drives. It is listed as essentially a Plug-&-Play solution, with the software included as ready to install and Go – in other words, plug in the included USB cable, and install the software on the USB thumb drive.

The adapter can be used for 5.25- and 8-inch drives as well, provide they have their own power supply..

Greaseweazle allows versatile floppy drive control over USB. By extracting the raw flux transitions from a drive, any disk format can be captured and analyzed - PC, Amiga, Amstrad, PDP-11, musical instruments, industrial equipment, and more. The Greaseweazle also supports writing to floppy disks, from a range of image file formats including those commonly used for online preservation (SCP, ADF, IPF, DSK, IMG, HFE, etc).

Features of the V4 Adapter: 

Integrates into Current WinUAE (4.9.1+) and allows use of real Amiga disks with Disk Change detection, to be read and written as part of WinUAE's FloppyBridge support.

• Reads, stores and writes 3", 3.5", 5.25", 8" disks (with suitable drive and cable), including copy protected disks
• Buffered outputs for communicating with older 5.25" and 8" disk drives
• Integrated power connector for directly powering most 3.5" disk drives
• Write-enable jumper can be removed for safer preservation of precious vintage disks
• Supports flippy-modified 5.25" drives
• 3 user-definable outputs (e.g., 8" interface REDWC signal)

While the USB interface supplies the required 5V power for the included 3.5” drive, if the GreaseWeazle adapter is used with other drives, they will need their own power source

Concept:

Every magnetic disk, regardless of type or size, stores data by changing the orientation of ferro-oxide particles bound onto a durable and flexible plastic platter. The data itself is represented as “flux transitions” aka “flux reversals,” which indicate a change of the polarity of the magnetic field. Because it is impossible to actually read the orientation of the particles on the disk surface using the head designs used, the only way to define data is by flux changes. This requires the disk to be spinning because without movement, no AC current is induced in the head. The actual data is normally coded using a scheme like FM, MFM or GCR. While MFM is the most popular scheme (in fact it just survived long enough) used on floppy disks, there are many other ways to encode and represent logical 0 and 1."

This is what allows it to copy, store and write disk images with copy protection, using the SCP format (Flux Image).