commodore sx64 keyboard cable idea

On Fri, Apr 6, 2012 at 1:09 PM, Alexandre Souza - Listas <pu1bzz.listas at gmail.com> wrote: I would recommend a parametric CAD like OpenSCAD or FreeCAD to generate the shape. IIRC, it should be a small number of "cubes" subtracted from other cubes, so that's easy to code up. It's a passive switch matrix, like the C-64 and VIC-20 and PET, and since the ROMs are fundamentally the same as a C-64 (yes there are differences but I don't think they apply to the keyboard scanning routine), one could take a C-64 keyboard and wire up a DB25 adapter. Not portable, but it would work. For a "modern" keyboard, I'd recommend something like Jim Brain's adapter that has a silicon crossbar switch. We've been over that sort of thing on the list before, but the design constraints are that the scan routine runs every clock 'tick' (16.67ms on any C= NTSC machine) and strobes the matrix in a few uS, plus in the case of the C-64, the keyboard shares lines with the joysticks, so any keyboard adapter should play nice with those lines in particular. I don't think many people did in-the-box hacks with the keyboard scan lines, so as long as the IRQ scan routine works and the joysticks work, that would be a successful emulator. There are several techniques to do it; a silicon crossbar switch is a low-effort one. That's unfortunate. I hope some good news comes your way. -ethan