一、前言
由于 Jetson 系列开发板常作为自主无人机的机载电脑，而无人机硬件平台如 PX4 和 ArduPilot 等通过 MAVLink 进行发布无人机状态和位姿等信息，要实现机载电脑与 MAVLink 的通信，必须借助 Mavros 功能包，因此，本文主要介绍 Mavros 功能包的安装、配置与使用，主要参考
GitHub - mavlink/mavros at master
https://github.com/mavlink/mavros/blob/master/mavros/README.md#installation
Ubuntu 安装并配置 mavros （USB 连接）_ubuntu安装mavros-CSDN博客
官方给出了直接安装和源码安装两种方法，由于一般 mavros 安装并配置完成后不会轻易改动，且十分常用，因此比较推荐直接安装方法，本文也只介绍直接安装方法
二、Mavros 的安装
由于 Jetson Orin NX 的 JetPack 5.1.2 对应的是 Ubuntu 20.04，因此我们选择安装 noetic 版本的 mavros 功能包，终端输入
sudo apt-get install ros-noetic-mavros ros-noetic-mavros-extras -y
此时可以查看 /usr/share/ 下多了一个 GeographicLib 文件夹，其内容是空的，需要我们自己添加进去
进入 ~/Documents/ 目录，下载脚本文件
wget https://raw.githubusercontent.com/mavlink/mavros/master/mavros/scripts/install_geographiclib_datasets.sh
然后给下载好的脚本文件添加可执行权限，
sudo chmod +x ./install_geographiclib_datasets.sh
运行该脚本下载所需文件
sudo ./install_geographiclib_datasets.sh
如果执行报错，就直接去GeographicLib 官网下载（可能要挂梯子。。。）对应的三个包，下载得到三个文件夹：
1.GeographicLib geoids egm96-5 官网下载链接：
Download egm96-5.tar.bz2 (GeographicLib)
2.GeographicLib gravity egm 96官网下载链接
Download egm96.zip (GeographicLib)
3.GeographicLib magnetic emm2015 官网下载链接：
Download emm2015.zip (GeographicLib)
在 /usr/share/GeographicLib/ 路径下，将上面下载的三个压缩包解压后放在这个文件夹内，如下所示
至此，mavros 就安装成功了！
三、Mavrso 的运行
由于 Jetson Orin NX 与飞控（飞行控制器）一般有两种通信连接方式，一种是通过 USB 连接，另一种是通过串口连接，本节主要介绍 USB 连接方式使得 Jetson Orin NX 通过 Mavros 实现与飞控的通信。
由于时下最新的 Pixhawk 系列飞控为 Pixhawk 6X，因此本文主要介绍 Jetson Orin NX 与 Pixhawk 6X 的通信，其他电脑与飞控的通信方式也是相同的！
运行 Mavros 之前需要现修改 launch 启动文件
打开 /opt/ros/noetic/share/mavros/launch/ 路径下的 px4.launch 文件
可以看到 fcu_url 默认为 /dev/ttyACM0:57600，其中 ttyACM0 表示 USB 连接，57600 表示波特率，这里我们不对这个文件进行修改，而是在当前目录下新建一个 px4_ACM0.launch 文件
终端输入
cd /opt/ros/noetic/share/mavros/launch/
sudo touch px4_ACM0.launch
打开 px4_ACM0.launch 文件，
sudo gedit px4_ACM0.launch
将其内容改为
<launch>
<!-- vim: set ft=xml noet : -->
<!-- example launch script for PX4 based FCU's -->
<arg name="fcu_url" default="/dev/ttyACM0:921600" />
<arg name="gcs_url" default="" />
<arg name="tgt_system" default="1" />
<arg name="tgt_component" default="1" />
<arg name="log_output" default="screen" />
<arg name="fcu_protocol" default="v2.0" />
<arg name="respawn_mavros" default="false" />
<include file="$(find mavros)/launch/node.launch">
<arg name="pluginlists_yaml" value="$(find mavros)/launch/px4_pluginlists.yaml" />
<arg name="config_yaml" value="$(find mavros)/launch/px4_config.yaml" />
<arg name="fcu_url" value="$(arg fcu_url)" />
<arg name="gcs_url" value="$(arg gcs_url)" />
<arg name="tgt_system" value="$(arg tgt_system)" />
<arg name="tgt_component" value="$(arg tgt_component)" />
<arg name="log_output" value="$(arg log_output)" />
<arg name="fcu_protocol" value="$(arg fcu_protocol)" />
<arg name="respawn_mavros" default="$(arg respawn_mavros)" />
</include>
</launch>
至此，Mavros 的启动文件就配置完成了！
接下来将 Jetson Orin NX 与 Pixhawk 6X 通过 USB 连接，如下图所示
然后终端输入
roslaunch mavros px4_ACM0.launch
启动 mavros，发现报错
[FATAL] [1697177878.518260611]: FCU: DeviceError:serial:open: Permission denied
原因是 /dev/ttyACM0 没有可执行权限，需要先添加可执行权限，终端输入
sudo chmod 777 /dev/ttyACM0
然后再次启动 mavros
roslaunch mavros px4_ACM0.launch
结果显示
这表示 mavros 成功连接上了飞控！
此时可以查看 mavros 话题，终端输入
rostopic list
打印输出
/diagnostics
/mavlink/from
/mavlink/gcs_ip
/mavlink/to
/mavros/actuator_control
/mavros/adsb/send
/mavros/adsb/vehicle
/mavros/altitude
/mavros/battery
/mavros/cam_imu_sync/cam_imu_stamp
/mavros/camera/image_captured
/mavros/cellular_status/status
/mavros/companion_process/status
/mavros/debug_value/debug
/mavros/debug_value/debug_float_array
/mavros/debug_value/debug_vector
/mavros/debug_value/named_value_float
/mavros/debug_value/named_value_int
/mavros/debug_value/send
/mavros/esc_info
/mavros/esc_status
/mavros/esc_telemetry
/mavros/estimator_status
/mavros/extended_state
/mavros/fake_gps/mocap/tf
/mavros/geofence/waypoints
/mavros/global_position/compass_hdg
/mavros/global_position/global
/mavros/global_position/gp_lp_offset
/mavros/global_position/gp_origin
/mavros/global_position/local
/mavros/global_position/raw/fix
/mavros/global_position/raw/gps_vel
/mavros/global_position/raw/satellites
/mavros/global_position/rel_alt
/mavros/global_position/set_gp_origin
/mavros/gps_input/gps_input
/mavros/gps_rtk/rtk_baseline
/mavros/gps_rtk/send_rtcm
/mavros/gpsstatus/gps1/raw
/mavros/gpsstatus/gps1/rtk
/mavros/gpsstatus/gps2/raw
/mavros/gpsstatus/gps2/rtk
/mavros/hil/actuator_controls
/mavros/hil/controls
/mavros/hil/gps
/mavros/hil/imu_ned
/mavros/hil/optical_flow
/mavros/hil/rc_inputs
/mavros/hil/state
/mavros/home_position/home
/mavros/home_position/set
/mavros/imu/data
/mavros/imu/data_raw
/mavros/imu/diff_pressure
/mavros/imu/mag
/mavros/imu/static_pressure
/mavros/imu/temperature_baro
/mavros/imu/temperature_imu
/mavros/landing_target/lt_marker
/mavros/landing_target/pose
/mavros/landing_target/pose_in
/mavros/local_position/accel
/mavros/local_position/odom
/mavros/local_position/pose
/mavros/local_position/pose_cov
/mavros/local_position/velocity_body
/mavros/local_position/velocity_body_cov
/mavros/local_position/velocity_local
/mavros/log_transfer/raw/log_data
/mavros/log_transfer/raw/log_entry
/mavros/mag_calibration/report
/mavros/mag_calibration/status
/mavros/manual_control/control
/mavros/manual_control/send
/mavros/mission/reached
/mavros/mission/waypoints
/mavros/mocap/pose
/mavros/mount_control/command
/mavros/mount_control/orientation
/mavros/mount_control/status
/mavros/nav_controller_output
/mavros/obstacle/send
/mavros/odometry/in
/mavros/odometry/out
/mavros/onboard_computer/status
/mavros/param/param_value
/mavros/play_tune
/mavros/px4flow/ground_distance
/mavros/px4flow/raw/optical_flow_rad
/mavros/px4flow/raw/send
/mavros/px4flow/temperature
/mavros/radio_status
/mavros/rallypoint/waypoints
/mavros/rc/in
/mavros/rc/out
/mavros/rc/override
/mavros/setpoint_accel/accel
/mavros/setpoint_attitude/cmd_vel
/mavros/setpoint_attitude/thrust
/mavros/setpoint_position/global
/mavros/setpoint_position/global_to_local
/mavros/setpoint_position/local
/mavros/setpoint_raw/attitude
/mavros/setpoint_raw/global
/mavros/setpoint_raw/local
/mavros/setpoint_raw/target_attitude
/mavros/setpoint_raw/target_global
/mavros/setpoint_raw/target_local
/mavros/setpoint_trajectory/desired
/mavros/setpoint_trajectory/local
/mavros/setpoint_velocity/cmd_vel
/mavros/setpoint_velocity/cmd_vel_unstamped
/mavros/state
/mavros/statustext/recv
/mavros/statustext/send
/mavros/target_actuator_control
/mavros/terrain/report
/mavros/time_reference
/mavros/timesync_status
/mavros/trajectory/desired
/mavros/trajectory/generated
/mavros/trajectory/path
/mavros/tunnel/in
/mavros/tunnel/out
/mavros/vfr_hud
/mavros/vision_pose/pose
/mavros/vision_pose/pose_cov
/mavros/vision_speed/speed_twist_cov
/mavros/wind_estimation
/move_base_simple/goal
/rosout
/rosout_agg
/tf
/tf_static
可以查看 IMU 频率，终端输入
rostopic hz /mavros/imu/data
结果显示
此时 IMU 话题频率为 200 左右，至此 Mavros 就安装完成了！