lattepanda sigma - enable onboard D connector BIOS (COM RS232/485)

Does anyone know how to enable the RS232 D connector (see board layout) in the BIOS settings?

I've recently purchased a Sigma board and in its BIOS I cannot enable COM0 (the only option

available for COM0 is DISABLED).

What I'd like to have is a working serial port from which I can have access to the bios settings

without using any keyboard and monitor.

Is this possible with the Sigma? 

Thank you for any help.