Greasweazle

Greaseweazle
File:Greaseweazle V4.1.jpg
Greaseweazle V4.1 unit
Developer	Keir Fraser
Release date	2018 (initial), ongoing revisions
Type	Floppy disk flux-level interface
CPU	STM32F103 / STM32F730 / AT32F4xx (varies by model)
Connectors	USB-C or Micro-USB; 34-pin floppy ribbon; power connector
Licensing	Open hardware & software (Unlicense for host tools)
Website	GitHub repository

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Greaseweazle is an open-source hardware–software system designed for imaging and writing floppy disks at the magnetic flux level. Developed by Keir Fraser, it supports a broad range of disk formats and is widely used in data recovery, retro-computing preservation, and digital archiving. Its openness, affordability, and compatibility have made it a recognised alternative to proprietary solutions such as KryoFlux.

Background

Greaseweazle began in 2018 as a personal project by Keir Fraser, known in retro-computing circles for developing open hardware and firmware for disk imaging. Initial versions used low-cost STM32F103 “Blue Pill” boards before evolving into custom PCBs with improved electrical protection, faster microcontrollers, and USB-C connectivity. The project has since fostered a community of contributors and users, including preservationists, hobbyists, and computing historians.

Specifications

Hardware Models

• F1 (Blue Pill): STM32F103 MCU; entry-level design.
• F7: STM32F730 MCU; adds 12 V support and faster USB transfer rates.
• V4 / V4.1: AT32F4xx MCU; USB-C, input protection, multiple-drive support, jumperless firmware updates.

Host Software

• Command-line tool gw implemented in Python 3.
• Compatible with Windows, macOS, Linux, and Raspberry Pi.
• Released under the Unlicense.

Disk Interface Support

• Standard Shugart- and IBM-interface drives:
  • 3.5-inch and 5.25-inch (34-pin)
  • 3-inch Amstrad (26-pin, via adapter)
  • 8-inch (50-pin, via adapter)
• Reads and writes MFM, FM, and GCR encoded formats, subject to drive compatibility.

Usage

A widely referenced Yann Serra Tutorial (April 2023) offers structured guidance on using the system.

Access Levels

1. Sector-level: User-visible data in block-mode images (.img, .adf, .st, etc.).
2. Track-level: Preserves formatting, sector layout, and copy-protection metadata (.imd, .edsk).
3. Flux-level: Captures raw magnetic transitions (.scp, .hfe) for exact reproduction.

Basic Commands

Reading an AmigaDOS disk:

gw read --format=amiga.amigados MyDisk.adf --drive=A

Writing an image back:

gw write --format=amiga.amigados MyDisk.adf --drive=A

Defaults are inferred from the file extension and cable position.

Supported Profiles

The gw tool includes predefined profiles for dozens of systems, including Acorn, Amiga, Atari ST, Commodore, IBM PC, Macintosh, MSX, NEC PC-98, and ZX Spectrum. Each profile specifies geometry, encoding, and a recommended image suffix.

Troubleshooting

• No Index – Incorrect drive ID or power issue.
• Track 0 Not Found – Insufficient drive power or incorrect drive selection.
• Flux Overflow/Underflow – USB interference; try another port or cable.
• Verify Failure – Possible disk damage; clean the disk and drive heads.

Advanced Use

• **Meta-profiles** (ibm.scan, raw.250, etc.) allow capturing arbitrary sector geometries.
• Reading 48-TPI disks with 96-TPI drives via --tracks=…:step=2.
• Flux-level archiving with --adjust-speed and --raw for copy-protected media.
• Support for certain “flippy” 5.25-inch disks via --fake-index on compatible drives.

Third-Party Tools

• **Disk Utilities** – .scp ↔ .ipf conversion.
• **HxC Floppy Emulator** – Conversion of exotic formats to/from .hfe/.scp.
• **SamDisk** – Meta-image format conversions.
• **a8rawconv** – Atari 8-bit image conversions.
• **Fluxengine** – Alternative imaging software.

Custom Profiles

Profiles are stored in diskdefs.cfg and can be extended with --diskdefs.

Importance in Preservation

Greaseweazle is widely used in retro-computing preservation workflows due to:

• Openness – Both hardware and software use permissive licences.
• Affordability – Uses commodity microcontrollers and standard cables.
• Compatibility – Supports many legacy formats across diverse computing platforms.
• Community resources – Documentation, tutorials, and forums assist users in data recovery.

Key People

• Keir Fraser – Project founder and lead developer.
• Yann Serra – Contributor of a widely used usage tutorial.
• Community contributors via GitHub, wiki, and forums.

Appendix: Supported Disk Profiles

Greaseweazle Host Tools
Developer	Keir Fraser
Latest release	1.6(28 September 2024)
Operating system

Click to show/hide full disk profile table from Yann Serra Tutorial

Adapted from the Yann Serra Tutorial, the following table lists selected supported disk profiles with geometry, encoding, and preferred suffixes. System Profile Sides Cyls RPM kbit/s Sect/trk Bytes/sect Encoding Size (KB) Suffix Acorn BBC acorn.adfs.320 1 80 300 250 16 256 MFM 320 .adm Amiga amiga.amigados 2 80 300 250 11 512 AMFM 880 .adf Atari ST atarist.720 2 80 300 250 9 512 MFM 720 .st, .msa IBM PC ibm.1440 2 80 300 500 18 512 MFM-HD 1440 .img, .dsk Macintosh 68K mac.800 2 80 VAR 375 12–8 512 GCR 800 .dsk ZX Spectrum zx.trdos.640 2 80 300 250 16 256 MFM 640 .mgt, .dsk NEC PC-98 pc98.2hs 2 81 300 500 9 1024 MFM-HD 1458 .hdm, .xdf Full extended tables for 3.5", 5.25", 8", and 3" formats are available in the official tutorial.

References