DataFlyer 2650 — 26-pin to 50-pin SCSI Adapter

A small PCB that plugs onto the 26-pin SCSI header of the Expansion Systems DataFlyer 1200 SCSI+ controller card and exposes a standard 50-pin IDC SCSI header on the opposite side, allowing connection to internal 50-pin SCSI devices such as the BlueSCSI v2 Desktop.

If one uses a 90° angled female 26-pin IDC connector on the underside, it can then be used with the Phase5 Blizzard IV SCSI kit instead.

⚠ Test status (read first): The DataFlyer 1200 SCSI+ and the Phase5 Blizzard IV SCSI kit share the same 26-pin header pinout, so this board works with both. (An earlier worry that the DataFlyer was mirrored came from an out-of-date NCR5380 datasheet; the correct datasheet for the 44-pin PLCC package matches, and this was verified with a multimeter against the 26-pin header.) Only v1.1 has been bench-tested on real hardware (with the Blizzard kit); v1.2–v1.4 are outline/routing fixes that have not been re-tested.

Initial work by highpuff @ ikod.se

This PCB was born from the need to have an BlueSCSI Desktop V2 mounted inside an Amiga 1200 machine in a Checkmate 1500 plus cabinet with a DataFlyer 1200 SCSI+.

Googling for 26pin to 50pin solutions brought up the work by highpuff. Go to his website ikod.se/scsi-cable for the original cable.

From there the initial design was made one tuesday evening using KiCad and Freerouting.

Physical design

• J1 (26-pin IDC female, 2x13): mounted on the bottom side of the PCB, plugs directly down onto the SCSI controller card's 26-pin male header.
• J2 (50-pin IDC male shrouded, 2x25): mounted on the top side of the PCB, accepts a standard 50-pin IDC ribbon cable to internal SCSI devices.
• Silk screen: the top 50-pin connector has a clear "PIN 1" arrow on the silk screen.

     ┌───────────────────────────────────────────┐
     │  ┌────────────────────────────────────┐   │   ← TOP side (F.Cu / F.SilkS)
     │  │ J2: 50-pin IDC male shrouded       │   │     50-pin ribbon to SCSI devices
     │  └────────────────────────────────────┘   │
     │  ▲ PIN 1                                  │
     │                                           │
     └─────────────────────┐                     │   lower-LEFT corner removed so the
                           │  ┌───────────────┐  │   board clears a wedge A1200 +
                           │  │ J1: 26-pin    │  │   Blizzard (SCSI cable exits left)
                           │  │ IDC female    │  │
                           │  │ (underside)   │  │   ← BOTTOM side (B.Cu / B.SilkS)
                           │  │ ▲ PIN 1       │  │     plugs onto controller card
                           │  └───────────────┘  │
                           └─────────────────────┘

Pinout source

The pinout mapping in this project is derived from:

1. The Apple/Amiga DB25 SCSI standard (also documented in the DataFlyer SCSI+ Users Manual, page 33)
2. The standard 50-pin SCSI-1 pinout
3. The IDC26-to-IDC50 mapping documented at iKod.se (originally for the Phase5 Blizzard IV SCSI kit, which uses the same convention)

See PINOUT.md for the full mapping table.

Files

• dataflyer-2650.kicad_pro — KiCad 10 project file
• dataflyer-2650.kicad_sch — Schematic (rev 1.4, all 76 pins labeled)
• dataflyer-2650.kicad_pcb — PCB layout (rev 1.4, manually routed + GND zones)
• PINOUT.md — Pinout reference table
• BOM.csv — Bill of materials with Mouser part numbers
• LICENSE.md — Licensing notice (CERN-OHL-S-2.0)
• CERN-OHL-S-2.0.txt — Full text of the CERN-OHL-S-2.0 license

Revision history

• 1.4 — Bugfix: PCBWay flagged that J1 pin 22 was not connected. The board has been manually routed to close the gap. It now measures ~79 × 27 mm (reverse-L outline with a small lower-left cut-out). Pinout unchanged; routing fix only.
• 1.3 — Bugfix: in 1.2 the front and back board-edge outlines did not match — the two horizontal step edges that run parallel to the connectors did not overlap between the F and B sides. Both sides now share the same outline (the lower-right tab edge was corrected). No schematic or pinout change — electrically identical to 1.2, same reverse-L design. Gerbers + drill re-exported (metadata now correctly reports rev 1.3). Outline correction over 1.2 (see the compatibility & test-status note at the top).
• 1.2.1 — Patch (no GitHub release per the policy below). PCB title-block cleanup: the title block previously still read rev 1.1 with a stale "T-shape" title/comment, so the exported Gerber metadata (.gbrjob ProjectId revision and the TF.ProjectId lines) reported 1.1 even though the silkscreen printed Rev 1.2. The title-block title/rev fields now reference ${BOARD_NAME} / ${BOARD_REV}, making the project text variables the single source of truth for both the printed silkscreen and the Gerber metadata. No schematic, routing, or outline change — electrically identical to 1.2. Note: the Gerbers in the tree must be re-exported from KiCad to pick up the corrected metadata.
• 1.2 — New reverse-L board outline (79.05 × 26.01 mm) that wraps around the Phase5 Blizzard SCSI kit. A full-width top band carries the 50-pin J2; the board extends down only on the right to form a tab carrying the 26-pin J1, with the lower-left corner removed. J2 is pushed further toward the rear of the A1200 to keep the SCSI cable clear of the keyboard where the case tapers toward the front. For DataFlyer 1200 SCSI+ mounting, the area to the left of the 26-pin connector (toward the PCMCIA slot) has been minimized as far as possible to avoid fouling the A1200 RF shielding. Known limitation: the SCSI cable still exits to the left; a future revision may rotate J2 180° so the cable clears the RF shielding. Schematic and pinout unchanged from 1.1.1 — outline/layout change only, electrically identical. (Hardware test status is tracked in the note at the top of this README.)
• 1.1.1 — Patch (no GitHub release per the policy below). Front silkscreen overhaul: board name and revision now driven by ${BOARD_NAME} / ${BOARD_REV} project text variables, github URL added, attribution lines split for readability. J1 pin 1 marker added on bottom copper (B.Cu, mirrored, bold). No schematic or routing changes — electrically identical to 1.1.
• 1.1 — Bugfix: tie SCSI-1 reserved IDC50 pins (20, 22, 24, 28, 30, 34) to GND. PCB: J1 moved ~3.5 mm inboard for cleaner routing (does not affect mating with DataFlyer 1200 SCSI+ or Phase5 Blizzard IV SCSI kit).
• 1.0 — Initial release.

Release policy

Tagged GitHub releases are published only for major (X.0) and minor (X.Y) versions. Patch versions (X.Y.Z) are committed to main only and aim to remain production-ready — the Gerbers in the tree on any main commit should be fabricable — but are not formally released.

Bill of materials

See BOM.csv. Total cost per board ~$3-5 plus PCB fabrication.

Termination

This adapter does NOT include termination resistors. The assumption is:

• The controller card itself terminates one end of the SCSI bus.
• The device at the far end of the 50-pin chain (e.g. BlueSCSI v2 Desktop) terminates the other end.

Licensing

DataFlyer 2650 — 26-pin to 50-pin SCSI Adapter Copyright (C) 2026 Arnljot Arntsen arnljot_arntsen@hotmail.com

Is licensed under CERN-OHL-S-2.0, see LICENSE.md for full details.