I am trying to configure PX4Flow with Pixhawk. I have followed the instruction and created /etc/extras.txt with the text "mavlink start -d /dev/ttyS2 -b 115200 -m custom" and connected the PX4board to TELEM2. it's still isn't working. I need help here. plz let me know what I am doing wrong. I am using windows7 and using both mission planner and QGroundControl software.