Pypilot motor output

[janne]

Hi, 
I am new to this and this and have a very hard time finding info about this... 
I just bought a moitessier hat 2 and a raspberry pi 4. I have installed open plotter and everything seems to work. 
 the communications between the programs seems to be set up from start so i assume open cpn and pypilot are communicating.
My goal is to set up a route in open cpn and have the boat follow it.

My questions; 
-What program outputs the directions for the motor driver? 
-And in what "form"(nmea?) is the output? 

I first assumed that the info when following a chart route went like this: 
Open Cpm -->  Pypilot --> motor
But the serial connections in pypilot however seem to only be inputs?

I have connected an arduino nano every to the raspberry via usb and i can find it amongst the serial connections but then how do i set it up as a motor output? 
I have some experience with arduinos and have controlled larger motors before and hoped it would be quite easy to read a direction from the raspberry pi and just drive the motor a bit... however the motor.ino seems very complex