The XoomFloppy was already a small success and went away like the proverbial warm rolls. But now more and more people asked if they could build the whole thing with the well-known interfaces of the ZoomFloppy, i.e. IEEE-488 and Parallel Port. So I sat down again and extended the XoomFloppy. The result was the XoomFloppy Pro.

 In the article XoomFloppy - The ZoomFloppy in thumbnail size I had already talked about the XoomFloppy in detail. It was gamasl about making a small version of the ZoomFloppy. So I had this board


shrunk so much that it became this circuit board:

XoomFloppy PCB Bestückt

Of course, the IEEE-488 and Parallel connection were left behind. Although I had used the contacts for the parallel interface as solder contacts, but since the whole thing was built into a small USB case, you would have to cut a hole in it and lead the ribbon cable out somehow. Also some had managed to grab the IEEE-488 connector, but for most this was too much fiddling.

But most of all, the XoomFloppy lost its charm of being so small. Then you could directly take the big model, the ZoomFloppy.

Unfortunately the ZoomFloppy is very expensive in Germany, and there is also shipping and import sales tax from the USA. That led me to fulfill the wishes of some people and make a complete replica of the ZoomFloppy.

Now, of course, I could have made it easy for myself to have the ZoomFloppy board make a few. The Gerber files are publicly available, so this wouldn't have been a problem. Unfortunately, the developer of this board has been a little wasteful with space, so this board is larger than 100x100mm. Up to this limit you can have boards made in China for very little money, but anything above that is extremely priced.

In addition, my actual intention was to shrink the ZoomFloppy. The goal was to build the ZoomFloppy with all interfaces, but as small as possible.

I came across another problem: The IEEE-488 or GPIB socket is no longer so easy to get. It is a technology from the 70s of the last century and the heyday is long gone. One can speak of luck that these sockets are still manufactured at all. Only such a bush alone costs about 15,- Euro a piece. And then the fixing bushes are still missing to screw in. These are traded in a similar price segment, which simply drives up the costs.

But now it is the case that in the Commodore world these connections could be found on peripheral devices like floppy disks and printers, but not on the CBM computers themselves. There was a simple PCB connector, which looks very similar to the userport connector of the Commodore C64 at first sight. Presumably Commodore did this for cost reasons as well.

IEEE 488 Schnittstelle an einem CBM Gerät

And with the Commodore disk drives and printers there was always a corresponding cable included, which on one side had the typical IEEE-488 connection but on the other side exactly the counterpart for the above shown picture, which comes from a CBM computer.

So it was obvious to use exactly the same connector. Most owners should have a corresponding cable. And often you can find this cable in eBay for very little money. So I had everything together to get started.

I only had to add the IEEE-488 connector to the XoomFloppy schematic, which was done quickly.

Schaltplan XoomFloppy Pro 

And then, after a little fiddling, this circuit board was created, still as a 3D model.

XoomFloppy Pro Platine als 3D Modell

The electronics in SMD technology is completely on the underside. At the top you can see the parallel port ("SpeedDOS") as board connector and in DB15 version for all those who have a corresponding connector in their floppy. On the left side you will find the IEEE-488 connector. This is also a PCB connector and a 24 pin header. There a ribbon cable can be connected directly. And of course the IEC connector is now the right socket on the board. Not to forget the USB port.

A first prototype is quickly made.

XoomFloppy Pro mit Mini USB

Actually, the topic would have ended here if I had been asked to use a Micro USB port instead of a Mini USB. Originally my idea was to design the connectors analogous to the ZoomFloppy. But actually it was a good idea to use Micro USB, because these cables should be found in almost every household by now.

So I changed the connection.

XoomFloppy Pro

That was the final version of the XoomFloppy Pro, here as a green board. Later I also used a red version, like the XoomFloppy. But now the chapter can be closed.

Well, not quite. Because now I had the original problem again, like with the first XoomFloppy. The case was missing. To be able to buy something suitable was practically impossible. So I designed a case with the software Fusion 360 from Autodesk. I tried FreeCAD in the beginning, but the software is still so buggy and has so many limitations that I was almost driven to the edge of madness. Functions, which were natural in other programs, were completely missing. And then the constant crashes, which were often accompanied by the destruction of the model, made me change.

And with Fusion 360, I was able to quickly design a practical and handsome case:

XoomFloppy Pro 3D Modell

The whole thing then printed on a 3D printer, can really be seen.

XoomFloppy Pro im Gehäuse

Only the post plug has to be extended. For this I simply used a 40.pole socket strip with long connection legs. These are used with pleasure for the Raspberry Pi and are everywhere easily and inexpensively available. I shortened it to 24pol. and put it through the case. Depending on how good and exact the printer is, this fits problem-free. Sometimes you have to widen the small holes a bit. The easiest way to do this is with a small hand drill. 

The LED must also be left a little longer so that it can be flush with the top of the housing. The easiest way is to insert the socket strip into the housing. Then insert the LED flush. Then put the PCB carefully onto the socket strip and insert the two legs of the LED through the contacts provided. Then the LED can be soldered and the other half of the housing can be put on. With some pressure the whole thing closes and holds without screws.

For those who like to rebuild the whole thing, I've put the Gerber file in the download area as well as instructions for assembling the board. There you can also find the STL files, if you want to print the case.

The assembly list for the XoomFloppy Pro is as follows:

  • Microprocessor ATMega32u2-AU (U1) / TQFP-32
  • Level-Shifter 7406D (IC1) / SOIC-14
  • Capacitors
      • 2x 100nF (C1, C5) / 0805
      • 1x 1μF (C4) / 0805
      • 2x 22pF (C2, C3) / 0805
  • LED, blue (D1) / 0805
  • TVS-Diode USBLC6-2SC6 (DZ1) / SOT-23-6
  • PTC-Fuse Polyfuse 1206L150 (F1) / 1206
  • Resistors
      • 6x 100kΩ (R2, R4, R6, R8, R10, R11) / 0805
      • 1x 10kΩ (R15) / 0805 
      • 1x 220Ω (R12) / 0805
      • 2x 22Ω (R13, R14) / 0805
      • 5x 4,7kΩ (R1, R3, R5, R7, R9)) / 0805
  • Quartz 16MHz (Y1)  / 5032-2pin
  • MicroUSB Connector (J2) / Wuerth_629105150521
  • Pin Header 2x12-pol. RM2,54 (CN4)
  • DIN-6 Connector (J1)  / Lumberg 010599
  • D-SUB 15 Connector (CN3) / THT

The files for this project can be found in the download area. 

If you have any questions or suggestions, please feel free to leave a comment or contact me via the contact form.

Have fun with the replica!

I still have some circuit boards left. This can be requested for a small contribution towards expenses: PCBs


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