Preserving a floppy disk with a logic analyzer and a serial cable | Hacker News Reader

Preserving a floppy disk with a logic analyzer and a serial cable

chzsoft.de

107 pointsjnord30 comments

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Appreciate how the article documents the physical side of floppy interface and how a track is selected and read.

Then there's the (several) formats of tracks and sectors, which are left out of scope.

Mature open-source alternatives include GreaseWeazle[0] and FluxEngine[1].

They are also cheap and effective, based on off-the-shelf parts.

0. https://github.com/keirf/greaseweazle/wiki

1. https://cowlark.com/fluxengine/index.html

The cheapest Saleae Logic Analyzer costs $499.

https://www.saleae.com/products/saleae-logic-pro-16

A Greaseweazle costs like $35.

That being said, it's always fun to hack around using the tools you have lying around. Put money already spent to good use.

There are much cheaper logic analyzers out there.

I would suggest as the starting point to look at sigrok's supported hardware table[0].

I personally own a bunch of the cheap 8ch 24Msps saleae clones, which are typically below $10. I would recommend the one from muselab as it has open sourced its design.

The next step, the DSLogic, of which I have a 200Msps 16ch model.

0. https://sigrok.org/wiki/Supported_hardware

I would recommend the one from muselab as it has open sourced its design.

The original Saleae, USBee AX, etc. are basically the Cypress FX2 reference design.

If you already have a logic analyzer, are interested in the details, and maybe are facing a tricky disk with physical damage or creative copy protection, TFA may be helpful. If you just need to read disks without hassle and expense, a Greaseweasle or another adapter us likely a more suitable choice.

How does $5 sound?

https://hackaday.com/2022/07/07/pico-makes-capable-logic-ana...

or maybe $1 with free shipping?

https://hackaday.com/2024/04/15/logic-analyzers-decoding-and...

Yep. I have a Greaseweazle and a Central Point Copy II PC Deluxe Option Board (and regular). Greaseweazle is largely the way to go. It's important to use the highest-fidelity method on the best FDD with the highest SNR because using a floppy disk causes wear to the media. Age also plays a factor.

I also have TEAC (2.88M, 1.44M, 1.2M, 720K, 360K, and SCSI versions), Sony, and various other FDDs.

I remember it used to be $200 for a Saleae logic 8. Their margins on that hardware are insane..

you're really paying for the software, imo

As a great alternative there are a handful of very cheap Saleae knock-offs using the same series of Cypress/Infineon logic chips, and they work well with e.g. Sigrok.

Very cheap knock-offs have same CY7C68013 usb interface chip, but lack an FPGA that original Saleae has, so can't capture quite as fast.

Plenty fast enough for a floppy bit-stream, of course.

Note that the knock-offs are clones of the original ~10 year old Salae Logic design, which also used the CY7C68013 without an FPGA (and had smaller margins than their current design, it only cost ~$100). They added the FPGA as a way of differentiating their products from the clones after they started becoming widespread.

I would pay excellent money to get my hands on the floppies that held my childhood programs. They're long gone.

So if you're just getting started today, I recommend you keep copies of everything you do. It's fun to go back and look at, and maintaining those copies is a lot easier to do than it was in the 80s.

Fun-fact the last floppy disc was made in 2011

Also the BBC seems to be running an odd number of floppy stories lately?

https://www.bbc.com/future/article/20240510-floppy-disks-why...

https://www.bbc.com/news/articles/cx82407j1v3o

Reminds me of the applesauce project for Apple ][ disks; https://overcast.fm/+BRm0EGSWs

Would not the best way to scan a deteriorating? floppy disks is with a magnetic flux measuring tool that flies very close to surface of floppy , but not touching the floppy. Recording the analogue signal, generated a require a big storage space .....

That's what people do with tools like Kryoflux; the head of a floppy drive doesn't touch the disk, it floats above it and picks up the magnetic flux. https://www.youtube.com/watch?v=UxsRpMdmlGo covers a lot of it.

The head of a HDD floats, FDD heads slide on the surface.

For archiving a very old floppy, you don't want to touch the surface if you can help it to avoid causing any additional wear.

Have you come across any ways to achieve that out of interest?

Kryoflux had special drives for preservation but I don't see them in their store anymore. So no, sorry.

Special in what way? The most special thing about Kryoflux was their EULA claiming _every bit of data imaged with Kryoflux hardware belongs to Kryoflux_

https://www.reddit.com/r/vintagecomputing/comments/buyj9f/ti...

Special in setting the jumpers to disable writing before sending them to customers, probably.

I believe kryoflux license / EULA is what triggered Keirf to write GreaseWeazle.

Now, GreaseWeazle is vastly superior to kryoflux.

A possibel way, I have not read the paper yet.

Found this promising material https://www.researchgate.net/publication/371624900_The_do-it...

Found via google search with words >>DIY 3d printer Floppy Disk, MAgnetic flux<<

( I understand it would produce massive amounts of data, since it is recording the analogue value of the magnetic flux level readings. )

Thanks a lot, will have a look, that sounds very interesting!

Looks like this would require ?3? orders of magnitude higher resolution to start resolving data on floppies. Least dense DD disk is ~6000 bits per inch, ~240 bits per mm.

Thank you for the correction. Either I never knew that, or I had indeed crossed the wires about how they work.

The graphs would be easier to read for somebody not already familiar with floppy drives if the signals (e.g. Step, Index0) were marked with direction, i.e. is it input to the FD or output from it.

This is extremely cool, but isn't imdisk supposed to do the same?

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