Status 7/4/2020: Partial build...
Most of the Samtec headers arrived (courtesy Digikey). A few are still on back-order (probably built-to-order). However, I have enough parts to make a partial assembly and check the fit... So far, looks great!
Top side (Arduino CPU plugs in on this side):
Bottom side (Arduino shield(s) plug in on this side):
Here's an Arduino Mega-2560 attached:
You can see the 2x10 header there... that's where you install a little jumper across pin-pairs - thus connecting the CPU pins to the SHIELD pins. When you need to diagnose a problem and disconnect a signal - just remove the jumper!
And the bottom side, all I had handy was an Ethernet shield, but you get the idea:
Another view of the whole assembly:
Status 6/28/2020: Ordered parts from Digikey!
So pricey these $amtec headers! I've got to find a less expensive solution (but mechanically identical). For now, I just want to build a couple of boards to prove that everything fits together nicely when stacking together with a Mega-2560 and an appropriate Mega-sized shield board. One of my new industrial-control boards is arriving in a few days - and having this interposer board would really help with debugging (which is why I designed it!).
Status 6/26/2020: Blank PCB fabs arrived!
See below. All I need now are a handful of headers!
Status 6/8/2020: Blank PCB fabs are on order!