Can you spot what the 2 boards have in common?
They are both small, but this is not the only common point...
- It is not the HDMI connector (FunKey doesn't have HDMI output),
- not the USB connectors (FunKey has a low-profile PCB edge mid-mount model),
- not the CSi camera interface (FunKey does not have it either, although its CPU has this capability)
- CPU is of course different, since the RPi Zero BCM2835 is not available for retail
- DRAM integration? Yeah, but not quite: the RPi has a PoP( Package on Package) Elpida B4432BBPA-10-F 4GB DDR2 DRAM, the FunKey has an unknown SiP (System in Package) 512MB DDR2 DRAM
... Yes it is: the microSD Card connector! Both boards are equipped with a Molex ref. 104031-0811.
It is a pure coincidence, though. Our primary motivation for choosing this (rather expensive) connector was its low profile: only 1.42 mm height, whereas most common connectors are ~1.9 mm height. And overall size too: only 11.95 mm x 11.40 mm, while common ones are more in the 14.70 mm x 14.50 mm ball park.
It is just a simple manual "PUSH/PULL" type (i.e. no bi-stable "PUSH/PUSH" mechanism that would take more space), but we don't care, as in the FunKey, the micro SD card is not meant to be removed anyway.