Dear people,
I do have:
- pixhawk 4 mini.
- Jetson TX2
- Ubuntu 16.04 installed
- Qground version v3.5.6
- PX4 firmware 1.9.2 instaalled on QGCS
I have created a hostpot in the drone side according to this link:
On the SDcard side under the /etc/extras.txt
mavlink stop-all
mavlink start -d /devttyS1 -b 921600 -r 20000 -m onboard
The mavors launch looks like this:
<arg name="fcu_url" default="/dev/ttyTHS1:921600"/>
<arg name="host_ip" default="host_IP" />
<include file="$(find mavros)/launch/node.launch">
<arg name="fcu_url" value="$(arg fcu_url)" />
<arg name="gcs_url" default="udp://@$(arg host_ip)" />
<arg name="tgt_system" value="$(arg tgt_system)" />
<arg name="tgt_component" value="$(arg tgt_component)" />
When I run the mavros launch file I get a message in QGCS
"Waiting For Vehicle Connection"
I have also tried the following command:
roslaunch mavros px4.launch fcu_url:="/dev/ttyTHS1:921600" gcs_url:="udp://@IP_host"
And I can see:
Got HEARTBEAT, connected. FCU detected!
[WARN] CMD: Unexpected command 520,result 0
WP: mission received
In the past I could get connected with no problem. Now I can not.
Any ideas or suggestions I would appreciate it 
Thank you all