I assume the big plastic connector next to the SATA is supposed to power a hard drive. Indeed I have a bunch of cables lying around that have 4-pin molex on one side, and the SATA power connector on the other.
But: all my cables are male on the molex side, and the Espressobin board is male, too!
Opening a random PC next to me reveals that its power supply provides female molex connectors, so my adapter indeed fits. Unlike the Espressobin.
What am I missing?