The rev1 base pcb with eZ80 support arrived today and I was able to partially populate it .. get the decoupling caps on there, the pull up resistors, and some headers. Firing up the Windows ZDS II based tools, was able to connect, upload a basic program, step through it and do breakpoints, memory and register dumps… awesome stuff. (And yes, I do intend to either run it under Wine and use the network based programmer, or build my own programmer… or maybe do something with bus-pirate, etc. Lots of options, but least of which is running another machine with Windows on it, just as an uploader.. bleh.)
So given the eZ80 seems to be working nicely, that implies keyboard and joysticks are likely okay; the bus stuff needs testing, but I've a pretty high confidence that stuff will work .. not much prototyped, but reasonably hard to screw up. Unless I crossed traces in the pcb or schematic of course, which is entirely possible, but easily fixed. Theres a couple uncertainties yet.. such as when the 5V and 3V items are chattering, if the low/hi voltages work out just right or not.. those that, if its a problem, is probably sortable by proper choice of HC, HCT or LS ICs, and I've got most of those in my parts-drawer already, so good to go. No, the only real concern is that I blew the wiring.. so, in pretty good shape, and we'll find out in awhile once I get some of the testing code in place.
I am exceedingly pleased at this point .. all the parts of the zikzak are on the bench, right now, just waiting code code to bring them to life! Going to be a fun few weeks .. if only I had more free time!
Picture of the current trio of boards (cartridge is not pictured.) The boards aren't connected together or fully populated here, but they can each do their own thing standalone.
edit: And another picture, without the GPU board, but with a cartridge plugged in; note that the cartridge slot connector is supposed to be mounted vertically but due to a drill-hole-size error in my layout, it doesn't fit right.. so as a workaround to continue testing, I just soldered it on the side :)