Since the serial port has only 3.3 volts signal level, a converter is needed
to connect the serial console. A MAX3232 could be used, but since most modern
PC's has no RS-232 serial port either, a USB to serial adapter that uses 3.3
volt signal level probably is the better choice.
I've decided to use a TTL-232R-3V3
from FTDI, which works perfect.
We need to connect only 3 Pins: GND, TxD and RxD. VCC is not used (and on the
TTL-232R-3V3 VCC is 5 Volts anyway)
The setting for the serial console is 115200 baud, 8 data bits, 1 stop bit, no parity