How to use your ZuluSCSI RP2040 as a USB-attached SCSI controller

rabbitholecomputing

Vendor The First
For anyone who might have a use case or interest in the ability to read and write to SCSI HDDs on "modern" machines/operating systems (any OS that supports USB Mass Storage Devices/flash drives), check out the latest ZuluSCSI firmware preview release, which enables most ZuluSCSI RP2040 boards to function as a USB-attached SCSI controller, allowing you to read *and write *to/from most SCSI block storage devices, such as HDDs/Zip/Jaz/MO/Syquest drives, with any modern OS/computer that supports USB Mass Storage devices. Due to hardware limitations, through is limited to around 800 kilobytes/second, but this is still significantly faster than many of the original Zip and Syquest drives that were shipped in the early-mid 90s.

If you already have an RP2040-based ZuluSCSI (red PCB), all you need to do use this functionality is update your firmware to the release at https://github.com/ZuluSCSI/ZuluSCSI-firmware/releases/tag/v2024.12.24-USB-MSC-SCSI and then remove the SD card from your ZuluSCSI, and connect your ZuluSCSI to a modern computer via USB. So far, I've tested this against a handful of different SCSI hard drives, a Zip drives, an AppleCD 300i CD-ROM drive, and a much newer Plextor SCSI CD-ROM drive. Tape drives are not supported at this time, as implementing support for emulating the tape transport commands requires additional effort and testing to get working reliably.

DVD-RAM drives should also work, but have not been tested. If you try it out and have questions about this feature/functionality, please ask them at https://github.com/ZuluSCSI/ZuluSCSI-firmware/discussions/491

Initiator-capable ZuluSCSI models​

ZuluSCSI models that do not support initiator mode​

  • All ZuluSCSI V1.0/V1.1/V1.2-based boards (blue PCB)
  • ZuluSCSI Pico Slim (DB25)
  • ZuluSCSI Mini
  • ZuluSCSI Compact RP2040 Rev 2022a
 

rabbitholecomputing

Vendor The First
There's also an operational USB serial console that logs some basic information about what is going on, which you can connect to using any terminal emulation app. The output will show you the device it detects, as well as quasi-real-time calculated transfer/throughput rates, and any errors it might encounter. You can purchase an off-the-shelf power supply to power any external drive with a four-pin Molex power connector for about $12. Sparkfun sells the TOL-15664 for $11.95, and Digi-Key also stocks and has them for sale for $12.50, at https://www.digikey.com/en/products/detail/sparkfun-electronics/TOL-15664/10650708
 

Realitystorm

Well-known member
I will need to test this with Basilisk II. I used to use Basilisk II and my USB zip drive to setup disks, with this, I should be able to setup my SCSI zip and Jaz drives using Basilisk II.
 

rabbitholecomputing

Vendor The First
I'm pleased to report that in the days since this initial announcement, this new functionality has been improved upon significantly, and has now been incorporated into the v2025.01.09 firmware release, the first ZuluSCSI firmware release of 2025. This release supersedes the previous preview release.
 
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