A few things have kept this project from flying higher...

• work
• other projects (damn, 33 now ! am I bulimic ?)
• the multiplexing logic of P1A
• board-to-board SMD connectors (I don't have the matching connectors and they are pretty expensive but I need a significant quantity...)

The last problem seems to be solved, while cleaning up the workshop...

I found a decent supply of 2×16 SMT connectors. They are pretty low-density but the 2.54mm pitch is good anyway. Contrary to the expensive FX8-100P, with the 0.6mm pitch, it is possible to run traces through the pins so all the signals are used, instead of just one half.

I bought the matching male and female pairs on eBay, many years ago:

They are about 8mm high when connected:

The main board will have a lot of long pins to stick through all the pages. With 40mm pins, that's about 10 pages. I'll have to find longer pins but they might be found for wire-wrapping and such. That will be my next eBay search.

Until then I can prototype up to 5 pages with the pins I already have in stock.

It's possible to cheat a bit by removing the black spacer after the pins are soldered, which makes 6 levels. I have other pins (more numerous) that can do 4 levels, eventually 5:

Now, the question is : how many of these 32-pins connectors does one page need ?