This rev2.1 mod allows the user to select if the external drive shall be DF1 or DF2. This external adapter also makes it possible to use them in pair: one for DF1 and one for DF2. Unfortunately Retro Ninja's adapter was lacking this feature (despite the passthrough connector - RN's adapter allowed only DF1..)
The TH components were replaced with SMD for saving PCB space. The unused inputs of the logical ICs are tied to ground or +5V, so there is no floating inputs and outputs. Also with this revision it is possible that no SMD component is needed if the adapter is used only with a Gotek drive (only ext floppy DSUB23 connector, power and floppy socket needs to be soldered).
The PCB is preconfigured: the Gotek option (no SMD) and DF1 drive is selected.
Detected issues:
- DF1 is not routed to the passthrough connector, so in case of two drive configuration it is not possible to configure the second drive to DF1
- Power cord is twisted while connected to the drives, so order of the pins should be reversed
- 24 pin pinheader socket for the passthrough cable is very hard to find, this should be replaced with a 26 pin header, but see future plans...
- Couldn't find straight floppy power connector and didn't want to mount a simple 1x4 pinheader (I wanted to avoid the accidental reverse connection), so I soldered the power cable directly to the PCB. That is also not safe as the cable can break after a few bending. (I used hotglue to protect cable from bending and breaking - but that is pretty ugly).
- 74LS00 is not open collector output logic, so having two of these modules fully populated with SMDs is probably not a good idea. 72LS00(74HCT00) should be replaced with a 74LS03 (same pinout, opencollector output). THIS NEEDS TO BE TESTED!
Other plans for the future:
- I would remove the passthrough connector and attach a simple second floppy connector for DF2. I guess there are enough logical gates available for DF2 onboard.
An adapter that allows external connection of Shugart floppy disk drive (in theory) or Gotek drives (tested)
This is work in progress and the first revision of the board is just a proof of concept. It has only been tested with a Gotek USB emulator. It was designed to plug directly into the external floppy port of the Amiga and connect a Gotek USB emulator with a 34-pin IDC cable and a power cable. The floppy connector on the board is rotated so a floppy cable can go in a straight loop to a Gotek laying on top of the Amiga. It should also be possible to mount the adapter in an external case but the floppy cable would have to be turned 180 degrees to match the connectors of the board and a Gotek. It would be pretty hard to fit a floppy power connector inside a case using the current design but the power cables could be soldered directly to the board.
J1 is the male 23 pin D-sub connector that plugs into the external drive port on the amiga. Pretty hard to find these today but it looks like new ones will be manufactured soon.
J2 is a male header for connecting the floppy cable. Connector can be straight or right angle, open or walled depending on what you got and what you want.
J3 is for floppy power connector. Cables can be soldered directly to board if needed.
J4 is the passthrough connector for a second or third external drive. Connect first row of pins on header (1...23) to first row of pins on female D-sub (1...12). Connect second row of pins on header (2...22) to the second row of pins on female D-sub (13...23). Warning! I have not tested this functionality yet as I don't have a female 23-pin D-sub. Try at your own risk.
This design was based on information gathered from Amiga System Programmer's Guide by Abacus and from the scematics for the A1020 drive. Designed with Fusion 360. Gerber files and Eagle schematics included.
| Component | Pcs | Name | Comment |
|---|---|---|---|
| 74LS00 | 1 | IC1 | 74HCT00 works fine |
| 74LS74 | 1 | IC2 | 74HCT74 works fine |
| 100nF ceramic capacitor | 2 | C1, C2 | |
| 1k resistor | 4 | R1, R2, R3, R4 | |
| 12k resistor | 1 | R5 | |
| D-sub 23M connector | 1 | J1 | D-sub This connector is pretty hard to source at the moment. Try eBay |
| 34-pin male header | 1 | J2 | 2x17 pin 2.54mm pitch. For floppy cable IDC connector |
| 4 pin header | 1 | J3 | 2.54mm pitch. For floppy power cable connector (or solder cables directly to board) |
| 24-pin header | 1 | J4 | 2x12 pin 2.54mm pitch header for outgoing connection to next drive in chain. For example IDC to DB23F. D-sub 23F connectors were manufactured by Unicorns and can't be found today |