When designing the NANO hardware I did include something for future use that has not been operational so far. Being buried between the two PCBs it is not easy to see, but I thought that some of you might have discovered it. But no one did so far
So lets start some guessing game, what this might be. To make it more easy I add a picture of a "topless" NANO, where the base PCB can be seen in its full extent.

- mbnano-topless.jpg (379.26 KiB) Viewed 3362 times
to be continued...