SERVICE port
The serial console terminal on boneIO Black controllers from version 1.0.
SERVICE port
From version 1.0, boneIO Black controllers have a SERVICE terminal with three pins: TX, RX and GND. It is the controller's serial console (UART) — a terminal into its Linux system, used for diagnostics and repair when the network or the panel does not answer.
Do not connect anything to it permanently. It is for servicing only. There is no +3.3V pin: the port does not power the adapter you connect.