With asking prices for these adapters being kind of absurd, I figured it might be helpful to consider reverse engineering one. It seems like a couple of special purpose ICs, a ROM and a surprising amount of passives. I don't think I'm up for the challenge of reverse engineering it, but figured some photos and IC info might be helpful if someone else wants to try.

The main ICs are Shuttle EUSB-01 & Shuttle EUSB-S1. I couldn't find data sheets for these. Please post them here if you can.
I'm also not sure of the ROM size, but will dump it if there's interest.

At a guess, this is a rebadged SCSI controller chip plus microcontroller. Having the ROM dumped is a step toward figuring out which architecture the CPU is.

That would be awesome! Something to hook up SCSI scanners, hard drives, etc., to the G3 and G4 computers. :) I can imagine how that would be neat under macOS 9.

One caveat I am wondering about is that the G3 and G4 USB 2.0 interface only have USB 1.1 support under macOS due to a lack of a driver to run at USB 2.0.

I suspect that they're bit-banging out SCSI from the EZUSB chip(s) much like BlueSCSI, RaSCSI, and SCSI2SD do, just in reverse. The BlueSCSI hardware could probably be reprogrammed to pass SCSI data in & out the USB port if someone finds a good driver interface to copy. I don't think there is anything extra besides a different firmware to act as a SCSI initiator instead of a target.
USB Attached SCSI is a thing, but it looks to be mostly for accessing SSDs faster on USB3 so there's no telling what the drivers in Windows 10 and OSX will do if they see scanner commands. OS9 won't have a UAS driver at all so maybe copying one of the period appropriate device's communication protocol would be in order.

The BlueSCSI hardware could probably be reprogrammed to pass SCSI data in & out the USB port if someone finds a good driver interface to copy. Click to expand...

Neat idea. @eric have you considered that as a feature before?

I didn't want to volunteer Eric for more work, but it could be a handy debugging tool to have a USB-SCSI bus sniffer or be able to replay transactions against development code.

great idea!

note the pins touching or almost touching ....

Yeah, that needs to be addressed @Elemenoh. Did you have any issues using it before? Hmmm. Weird.

Yeah it works. I might have hit those pins when removing the sticker on top of the IC.

>> luminescentsimian said:

The BlueSCSI hardware could probably be reprogrammed to pass SCSI data in & out the USB port if someone finds a good driver interface to copy. I don't think there is anything extra besides a different firmware to act as a SCSI initiator instead of a target. Click to expand...

Defiantly would be possible, but would take time/effort. If someone wanted to take a stab at it, go for it!

even though I know he has like 8045 projects on his plate, @jcm-1 !

>> tom_B said:

even though I know he has like 8045 projects on his plate, @jcm-1 ! Click to expand...

NOICE. Thanks for thinking of me. I am NOT a programmer. I only play one in my head. Could I do it? Probably. Would it happen fast or work correctly or have intelligent after-sales support. Absolutely not.

>> eric said:

Defiantly would be possible, but would take time/effort. If someone wanted to take a stab at it, go for it! Click to expand...

The MSX Rookie Drive uses a part called a CH376 that seems to be meant to make it easy for microcontrollers to read off USB sticks. That data sheet could be a good place to start?

Hello everybody,
this is my first post here and I hope to be in the right place. I have this exact USB-SCSI adapter, the SCM CM-S18 but only with OS 8.6 drivers and I am struggling to use it on OS 9.2.2 because it requires updated drivers I cannot find anywhere on the Net. The Wayback machine keeps to report error 302 every time I try to dig in scmmicrosystems.com and shuttletech.com snapshots so no luck in this direction. The big problem is that every adapter based on this exact chipset was customized for a particular brand so I have actually found updated OS9 drivers but NOT for this specific adapter and they won't load in OS9 (the infamous "eUSCSI Bridge Ver 1.11" requester when I plug in the device) so if I use the 8.6 drivers there they will crash the Mac at System extensions loading.
Now, the Castlewood USB-SCSI adapter has this exact plastic shell (plus the branded label) and I think their OS9 drivers could work out of the box also for my adapter BUT in the various installers I have found on the Net there was no signs of those drivers, only the utilities for the ORB units.
My question is: has the Castlewood USB-SCSI adapter ever worked in OS9? If yes, could someone kindly sent me the needed OS9 extension to activate it?
Many many thanks advance...

Just stumbled over a separate project trying to design and actually implement a low cost USB to SCSI adapter based on a teensy board here:

https://github.com/svenschnelle/teensyscsi

While the last update was done three years ago, there is already quite some amount of code. Actually the amount of code is a rather impressive!

There is also an accompanying thread by its developer on a German retro computing board here:

https://forum.classic-computing.de/forum/index.php?thread/24720-low-cost-usb-scsi-adapter/

Apparently the developer has already created fully working prototypes in actual hardware. And since his needs have been covered no further work seems to be done anymore. He claims that this adapter is able to read/write from/to a MO drive and hard disks.

A low resolution photo from above mentioned forum thread has been attached.

A pity this can't be bought.

Looks like someone is actually starting to "Implement a USB->SCSI Bridge Mode for BlueSCSI":

github.com/BlueSCSI/BlueSCSI-v2/issues/212