This project started about 10 years ago and has had more starts than Phar Lap (Aussie joke). Yet more processor PCBs made recently. The core processor has been changed to a Raspberry Pi Pico, partly because it has castellated pads so it can be soldered directly to the QUUB board, and partly because I think that there is a much larger following and body of work out there for that particular processor.

Here are five of them stacked, giving some idea of where the QUUB name came from  Of course one would not stack five MCU boards, I just wanted to check the mechanical aspects of the idea.