BCM50 Serial TTL-Level console on board.


    RX                3.3v     Enbl 
     °        °        °        °
                                |
    TX                GND       |  <-- jump to enable
     °        °        °        °

You must use a 232-TTL converter, and fit the 
jumper to the rightmost two pins prior to power 
on, for the presence to be detected. 

The console uses 115k N81.