Raspberry Pi Floppy Driver Uncovers Fishy Secrets

A forum post by New Zealand electronics enthusiast [zl2wrw] about retreiving waypoints from a mysterious floppy disk caught our eye. The┬ánavigation system on his friend’s fishing boat had died and was replaced. But the old waypoints were stored on a 3-1/2 inch floppy disk that was unreadable on a normal PC. Not to be deterred, [zl2wrw] then looked for another solution — apparently a list of hot NZ fishing spots is worth quite the effort.

The tool he discovered, and the main point of this story, is the bbc-fdc by [Jasper Renow-Clarke] aka [picosonic]. [Jasper] made this project to read 5-1/4 inch Acorn DFS floppies from his BBC Micro. But bbc-fdc can be used to read a variety of floppy disk formats, such as DOS, C64, Apple II, and others It can also just capture raw magnetic flux transitions on the disk, blissfully unaware of any logical structure to the data. We recently wrote about another Raspberry Pi Floppy Drive Controller project┬áby [Scott Baker]. What sets [picosonic]’s project apart is that he’s not using an FDC controller chip here. The only interface electronics is a couple of open-collector 7406 ICs. Data is read using the SPI peripheral. If you need to archive old floppy disks or do a forensic analysis of unknown disks like [zl2wrw], then one of these two projects will almost certainly do the trick.

Meanwhile back in New Zealand, [zl2wrw] discovered that the floppy format was standard (Modified Frequency Modulation, MFM) by examining the raw flux dump. However, the filesystem was a mystery — it didn’t quite match any of the usual suspects. So [zl2wrw] dug into the hex dump of the data and figured out enough of the structure to manually recover the waypoints. Subsequently, a user on the forum found a document describing the file system used by Furuno GPS units, which proved to be a close match albeit after the fact. Alas, [zl2wrw] hasn’t publish the coordinates of those good fishing spots.

Have you had any successes (or failures) when it comes to reading data from old disks? Or have you encountered peculiar disk formats and/or file systems, where having a tool like this could have been helpful? Let us know in the comments below.

ULTIMATE – A Useful Tool For File System Hacking

Whether you’re at the hobbyist level or a professional, if you’re working on code for operating systems or file systems, tools can make or break the job. [Ben Lunt] is an enthusiast hacker himself, and found that over time, a series of useful utilities had proliferated beyond reasonable management. It was time to solve the problem – enter ULTIMATE.

ULTIMATE is a combination of a wide swathe of file system hacking tools that [Ben] had developed over the preceding years. Capable of dealing with most FAT variants, Ext4, ISO, [Ben]’s own FYS FS as well as other Linux ephemera, it enables a wide variety of common tasks to be executed from within a single program.

Capabilities of the tool are wide ranging. Files can be inserted into and removed from image files, boot records can be altered, and there’s even the ability to tinker with GPTs for UEFI-based systems. [Ben] has also experimented with the concept of the eMBR – an extended Master Boot Record with greater functionality for larger, modern hard drives.

ULTIMATE is a testament to [Ben]’s broad file system knowledge, and could likely serve useful to many hackers in the file system and OS community. Just be cautious, though – the software is still in an early stage of development. If you’re just getting started in this particular realm of tinkering, take our primer on file system forensics.