Just another quick post to say that I have the prototype PCB at home now, and with the help of a student got a power supply for it, and now I have it powering up at home:
As you can see, I have my genuine C65 keyboard (complete with missing top-printing of the keys) connected.
The C65 keyboard connector is a bit tight to move on the power-supply switch side, which we will re-work on the rev2 PCB:
Unfortunately the SD card adapter has developed a couple of dry-joints in transit from Germany, so I will need to take it back into work tomorrow and re-touch those. Hopefully it will then work fine.
After I have that all working, I'll start looking at the cartridge port and floppy connectors to verify that they function fine. Apart from a known signal direction wrinkle on the cartridge port, I am not expecting any particular problems there.
Then I will try to debug the problems with the keyboard interface that Falk discovered. I think it is ghosting due to the relatively weak pull-ups in the FPGA causing ghosted rows or columns on the keyboard interface. The solution there will probably be to have the real keyboard scanner in VHDL, populating an internal matrix representation that is actually scanned by the C64/C65 ROM. The internal matrix representation is already there, because it was required for the PS/2 keyboard interface.