Unable to start MAVLink properly on another serial port

Hi all,

I’m using a Pixhawk1 board. I wanted a MAVLink instance on another serial port. I modified the rcS to enable the MAVLink on the serial port 4 (/dev/ttyS6). Then I connected an FTDI and tapped the serial pins. Then I started qGC and saw that the communication was incomplete. The qGC was partly able to connect to the board. After this, the connection never completed. I tried this several times and wasn’t able to connect the MAVLink via serial. Please see the attached pic. It says: “Vehicle 1 did not respond to request for parameters”. This is the line in the rcS:

mavlink start -d /dev/ttyS6 -r 2000 -b 57600 -m config -x

Please help me out with the issue…
Thank you