Hardware Serial2 in Marlin (no replies)

Hi,

I am building a SLA 3D printer
[www.kvistholm.se]

Using a LCD display and a displaydriver (http://www.abusemark.com/downloads/dpadapter_rev1b.pdf)

To turn the display on and off is a crucial in my printing process.
And this can be achieved with the following simple code on my Mega2560 using Ramps pin 16,17
Serial2.begin(115200);
Serial2.println("control bl on");

The problem is that this not possible to do in Marlin FW due to the extended MarlinSerial .....
How do I solve this???