First buy all parts: parts.ods (OpenOffice calc format). For the PCB, if you want to produce more, and if you want the nice hard gold plated edge connector, contact the manufacturer I used for the first run, Hupperz. For the prototype I used Itead Studio. Gerber files, and Eagle schematic and board files: 4-layer.zip.
The only parts hard to solder by hand are the two QFN parts: the EMI filters and the oscillator. For my prototype I used solder paste, applied with a needle, then a hot air gun. But it works without the EMI filters, too, if you just solder wire bridges with very thin wires instead.
Parts orientations for reference, from my hand soldered prototype board and a PCB from Itead Studio:
After soldering you need to program the CPLD. Use a Xilinx Platform Cable (there are cheap clones on eBay), connect GND, TDI, TMS, TCK, TDO, and VREF to 3V3 on the left side (you can solder pin headers for it, or use pogo pins), connect an external 3.3V power supply and GND to 3V3 and GND, then start ISE iMPACT (included in the free ISE WebPACK edition, version 14.7) and open program.ipf (in directory cpld/kerberos, in the Kerberos Github repository). Note: If you are using Windows 8 or Windows 10, you need to fix the installation before you can open a project. Then right click on the chip and select "Program".
For the MIDI connector holes in the cartridge cases I used a 17 mm Flachfräsbohrer. For the guiding hole and the LED holes I used a 3 mm drill bit. At the top of the bottom case, I glued a square-cut acrylic spacer, 5 mm x 50 mm, so that the board doesn't bend when you plug-in a MIDI cable, and at the bottom of the case a 10 mm x 50 mm spacer, so that the cartridge case doesn't bend when you plug-in a cable when it is connected to the C64/C128:
For the guiding holes and the LED holes I used a template, from an unpopulated PCB, where the lower end was cut off so that it fits nicely in the case:
Then install the menu system and the software on the flash memory: on the C64 somehow start menu.prg, e.g. with a SD2IEC and select the transfer menu. Then connect MIDI-out of an USB MIDI interface with MIDI-in of the Kerberos cartridge, start the Kerberos App on a PC from a command prompt with the additional command line switch "debugging", download flash-dump.bin, change to the "MIDI config and test" tab, select your USB MIDI interface and flash it with "Upload flash" (when in transfer menu on the C64).
Finally you can print the sticker, see aufkleber2.ai (Adobe Illustrator format). Contact http://www.klebe-teufel.de for professional stickers, this is the company where the Kerberos stickers were made.
30. January 2016, Frank Buß