My Xerox 820 CP/M computer has a large external drive enclosure with two 8" SS/DD floppy drives in it. They have a "shugart" interface inside, brought out to a proprietary-but-documented 37-pin D-style connector. Because the data signals used by floppy drives changed very little over the decades (at least in the CP/M and PC worlds; Commodore and Apple users, don't @ me) all the signals mostly map closely enough onto IBM PC 34-pin connector.

I previously made a passive adapter board so that a "Gotek" floppy drive emulator could replace the drive enclosure, and it worked! (and is a LOT less loud than 2 8" floppy drives spinning all the time!!!)

That got me thinking: could I make a 2nd adapter board that would let me archive 8" floppies? Then, inspiration struck: I didn't even need a 2nd board design. Instead of fitting a plug ("male") connector on the board's top side, I could simply fit a socket ("female") connector on the board's bottom side.

Since I'd gotten 5 boards in my PCB order, I just had to wait for delivery of the connector and solder everything up.

Both archiving and writing worked on the first try, with greaseweazle host software and an Adafruit Floppsy prototype board; a genuine GreaseWeazle should work just the same.

You can grab the kicad design files from my xerox 820 repository on github and order them from the board house of your choice.

Soldering the PCB

• Take a 2x36 pin header strip and snip off a 2x17 portion of it, reseving the rest for another project
• Solder this header on the top side of the board (where the silk is visible)
• Solder a 37-pin receptacle ("female") connector on the bottom side of the board (opposite the silk)
• The "mod" area is unused
• The 4-pin floppy power connector is ununsed

Connecting the board

Plug the floppy enclosure into the "D" connector; this is polarized so it can go only one way. Then, noting the "pin 1" location on both the GreaseWeazle/floppsy and the converter PCB, connect a straight through 34-pin ribbon cable.

Invoking greaseweazle

First, install greaseweazle host software according to the directions, and install a greaseweazle-compatible firmware on your device. Check that "gw info" can find and report your device info; you may need to provide a "--device" flag to all greaseweazle commands if you are using a greaseweazle-compatible device, not a genuine greasweazle. (e.g., "gw info --port COM31")

To archive a floppy:

• For safety against unintentionally writing to a floppy, the Adafruit Floppsy has a write enable switch. Slide it to the "OFF" position.
• Insert a floppy. For Floppsy, use the "B" drive. For a genuine GreaseWeazle you can use either "A" or "B" via the --drive flag. 
• Create the disk image: gw read --format dec.rx01 cpm.img

When the process completes, you will be shown a summary of any parts of the floppy that could not successfully be read.

To write a previously read floppy image note that this will irrevocably destroy the data previously on the floppy:

• If you're using an Adafruit Floppsy, make sure the write enable switch is in the ON position
• The floppy must also be write-enabled. On 8" floppies, this is done by covering the "write protect" notch on the right side of the bottom edge. Some 8" floppies were manufactured with no notch, in which case they are never write protected (this is opposite to the situation with 5.25" floppies)
• Insert the floppy you want to write to. For Floppsy, use the "B" drive. For a genuine GreaseWeazle you can use either "A" or "B" via the --drive flag. 
• Write the disk image: gw write --format dec.rx01 cpm.img

When the process completes, you will be shown a summary of any parts of the floppy that could not successfully be verified. All 8" floppy media is decades old, and unreadable/unwritable sectors are an unfortunate fact of life.

On the internal organization of image files

These images come out in the correct format & organization to use with the flashfloppy configuration I posted on my earlier playground note. CP/M had some complicated rules relating to sector numbering & interleaving, and each manufacturer could actually use different formats & organizations from every other manufacturer! Different conventions for archival images can place the sectors in a different organization, so when it comes to using images from the internet you may have to use conversion software to make sure the data is in the correct order. Unfortunately, the only way to do this is by trial and error.

Parts