sd based scsi zip/jaz drive

[Chopsticks]

its something thats crossed my mind a lot over the last couple years (ive probably even mentioned it at times here too). to make a modern zip or jaz style sd scsi drive solution. basically a sd card scsi solution that has a fixed scsi id or better yet a set of jumpers like old scsi drives did to select a scsi id. that is hot swappable and allows one to insert a 'card' and have it mount on the desktop just like any other removable scsi drive would back in the day

i have a pretty good idea mechanically what to do with motors and a drive sled concept that could use a full sized sdcard or possibly a larger pcb containing a sdcard slot that physically mimics a zip drive disk be it fuil size or perhaps half size etc..

i was wondering if anyone had any thoughts or advice about how hard it would be to modify any of the current solutions be it zulu scsi or bluescsi to do this. being that the firmware is open source.

basic requirement would be to have a fixed scsi id, hotswap/card detect, breaking out whatever scsi commands for ejecting and inserting a card to a pin or two for the motors and card detect.

 

[finkmac]

you can already do that with zulu-based hardware

 

[Powerbase]

you can already do that with zulu-based hardware

Do they allow actually hot-swapping the physical SD card? I know they allow "swapping" the disk images on the sd card. Maybe I'm confused about what he's asking.

 

[Daniël]

Do they allow actually hot-swapping the physical SD card? I know they allow "swapping" the disk images on the sd card. Maybe I'm confused about what he's asking.

Yes, ZuluSCSI (and derivative forks) does have the ability to handle physical SD card hot swapping.

 

[olePigeon]

I saw someone make an SD card floppy drive. I think it'd be cool to build something that can do that. Take a real 800K drive mechanism and motor, modify it so when you insert a special floppy disk with an SD card instead of a floppy platter, it connects perfectly to the SD slot pins. Then when you eject it, the ZuluSCSI sends the eject command to the floppy drive and ejects the SD floppy.

 

[Daniël]

I saw someone make an SD card floppy drive. I think it'd be cool to build something that can do that. Take a real 800K drive mechanism and motor, modify it so when you insert a special floppy disk with an SD card instead of a floppy platter, it connects perfectly to the SD slot pins. Then when you eject it, the ZuluSCSI sends the eject command to the floppy drive and ejects the SD floppy.

Or design a new eject mechanism entirely, which has the benefit of not being reliant on fragile plastic gears
I know the Brewintosh project, a fully 3D printed Mac 128K replica with modern guts running an emulator, had that done to a generic USB floppy drive, to make the automatic eject work (alongside code changes in the emulator, so it sends the eject command to the microcontroller):

 

[ironborn65]

inspirational video

 

[Chopsticks]

Yes, ZuluSCSI (and derivative forks) does have the ability to handle physical SD card hot swapping.

from what i read it does allow hotplugging of a sd card. however in the case of a mac that would still require a bus rescan and will still pick the scsi id of whatever hdd images are on the sd card.

whats needed is for the firmware itself to report to the host (a mac in this case) as a fixed scsi id device with removable storage, regardless of if theres a sd card inserted or not.

inserting a sdcard would then trigger the card detect by the micro used (generally a pi pico these days) and it would in term issue scsi commands back to the mac host saying a disk is present and the mac would load it up on the desktop

dragging the disk to the trash i would assume the mac send a scsi eject command back to the pi pico.

the pi pico would then toggle a pin or some logic to a mini motor (maybe a solenoid or whatever else it used) that physically ejects the sd card.

----
@ironborn65 that does indeed look pretty cool, ill have to give that video a watch

 

[mogs]

This looks like fun. (Been a while since I've posted here, we've built a house and I've changed jobs).

The first thing that came to mind would be to make use of pogo-pins like the mag-safe connectors on old macbooks. I then imagined a PCB in the shape of a 3.5" floppy which includes a micro SD slot to fit in a modified drive mechanism (or a thin PCB to replace the spinning media in an original floppy case like the video above, the pure hackery in that video is impressive).

Of course a regular push-push SD socket would also work just fine as a removable media solution, and as described by @Chopsticks above the real challenge here lies in the firmware.

Next I wanted to see if anyone had implemented dual SD cards on a Pi-Pico, I found the no-OS-FatFS-SD-SDIO-SPI-RPi-Pico project, which as it turns out derived it's SDIO support from ZuluSCSI. The idea being a regular "internal" SD card with all the normal stuff, plus a place holder / config file for the removable media.

It looks like this may be challenging on the RP2040/Pico 1, due to the number of IO required to implement both SCSI and multiple SD cards.

A stretch goal might be to use a RP2350B with the additional 18 GPIO. The Pimoroni Pico Plus 2 appears to feature pin compatibility with Pico 1, while also conveniently providing a JST-SH header with additional SPI pins. Unfortunately this comes at the expense of WiFi expansion.
So physically at least, it could be placed into an existing Pico based xxxxSCSI carrier with an additional SD card on a JST-SH fly lead.

While I prefer the idea of reducing the number of physical SCSI devices on the bus, as I see this as introducing complexity that can be solved in firmware. A simpler first step would be to modify an existing xxxxSCSI firmware implementation to work as a stand alone SCSI device with removable media.

I'm unlikely to actually do anything to make any of this happen, making suggestions on electronics projects is literally my job now, I only hope that some of it is helpful.

m

 

[Chopsticks]

@mogs i dont think it would be to crazy firmware wise.. ive been pretty busy with life lately so i havent had much free time and to be fair im much better with hardware the writting C code. however i think the ZuluSCSI code already has alot of whats needed already there. the main thing at least for a a prototype solution is to see what avaliable IO is free on the Pi Pico and hard coding a scsi ID into the firmware. then adding some code to interpret the Eject and Insert Disk commands and toggle a pin on eject.
from what i understand ZIP drive suport is already supported, and CD drive too so i dont think it would to too difficult to adapt that.

my initial goal isn't really to have FAT16 support. i was still intending on using .img/.hda images due to the HFS data forks.
im mainly wanting to get a prof of concept running that i can build upon with a hardware solution that from the end user point of view fuinctions the same way a SCSI removable disk device of that era does like a Iomega ZIP or JAZ drive does