Connection the Pixhawk to TX1

ArduRover
1

Hi,
I would like to use the Pixhawk to control a Rover via ROS(with Jetson TX1).
But , I can’t connect the Pixhawk to TX1.
Follow is my matter.

Step.1 (launch roscore)
apsync@apsync:~$ roscore

Step.2 (launch apm.launch)
apsync@apsync:~$ roslaunch mavros apm.launch

Step.3 (check connection)
apsync@apsync:~$ rostopic echo -n1 /diagnostics

・・・
level: 1
name: mavros: FCU connection
message: not connected
hardware_id: /dev/ttyTHS1:921600
values:
・・・

↑:FCU connection is “not connected”

Could you tell me how to connect the Pixhawk to TX1.

<<>Environment>
・Jetson TX1(JetPack-2.3.1)+J120 board
-ubuntu(16.04.3 LTS)
-ros-kinetic-mavros(latest(0.21.0-0xenial-2 arm64))
・Pixhawk
-ardupilot(APM:Rover v3.1.2)

<<>Configuration>
1.Mavros configuration
<<>original>

<launch>
	<!-- vim: set ft=xml noet : -->
	<!-- example launch script for ArduPilotMega based FCU's -->

	<arg name="fcu_url" default="/dev/ttyACM0:57600" />
	<arg name="gcs_url" default="" />
・・・

<<>changed>

<launch>
	<!-- vim: set ft=xml noet : -->
	<!-- example launch script for ArduPilotMega based FCU's -->

	<arg name="fcu_url" default="/dev/ttyTHS1:921600" />
	<arg name="gcs_url" default="" />
・・・

Reference Web site
https://github.com/mavlink/mavros/blob/master/mavros/launch/apm.launch

2.Pixhawk configuration
(set by MISSION PLANNER)
<<>Full Parameter List>
SERIAL2_PROTOCOL = 1
SERIAL2_BAUD = 921
LOG_BACKEND_TYPE = 3
BRD_SER2_RTSCTS = 0

Reference Web site
http://ardupilot.org/dev/docs/companion-computer-nvidia-tx1.html#