This was my first design for Baffa-2 Homebrew Microcomputer project but I decided to prioritize a CP/M machine before. I had dedicated sometime to studying Grant Searle's ZX80/81 project and building the board designed by Wilco which has an excellent backporch solution using the LM1881 and went after other platforms.
After about 10 months, I decided to review and finalize the boards and try the solution. As I needed a new set of backplanes, I chose to design a cheaper version that is half the size and can be used in smaller projects like this one.
I am very grateful for the support provided by PCBWay that made the completion of this project possible.
This is a presentation video showing the initial tests:
The video board implements the slow circuit and replaces the ZX81 ULA IC. A detailed explanation about it is at Grant Searle's website. Also it has a jumper to switch between nomal/inversed screen and 2 backporch options (Searle's white restauration and Wilco's LM1881 solution).
RAM/ROM Board allows you to switch between ZX80 4kb rom and ZX81 4kb rom
I/O Board (Cassette and PS/2 Keyboard) adapts the Danjovic's Tek V2 solution to emulate the keyboard matrix using an arduino. It also can be used with the original membrane keyboard (SV1 and SV2 sockets - not soldered )
New Baffa-2 Backplane Lite