Pixhawk 4 flight control establishes connection with Up Board’s ROS

Pixhawk 4 flight control establishes connection with Up Board’s ROS

The purpose of establishing a connection between Pixhawk 4 and ROS:
to install the microcomputer and Pixhawk 4 flight control board on the drone to achieve autonomous flight of the drone

1. mavros function package

The Pixhawk 4 flight controller needs to establish contact with the microcomputer through the mavros function package in the microcomputer ROS, and then communicate through the mavlink protocol. Therefore, we must first install the Ubuntu system on the microcomputer and install the ROS and mavros function packages.

Here I install mavros according to the usage documentation of XTDrone Yuque

1. Depends on installation

sudo apt install ninja-build exiftool ninja-build protobuf-compiler libeigen3-dev genromfs xmlstarlet libgstreamer1.0-dev libgstreamer-plugins-base1.0-dev

pip2 install pandas jinja2 pyserial cerberus pyulog==0.7.0 numpy toml pyquaternion empy pyyaml 
pip3 install packaging numpy empy toml pyyaml jinja2 pyargparse

Install mavros

sudo apt install ros-melodic-mavros ros-melodic-mavros-extras

wget https://gitee.com/robin_shaun/XTDrone/raw/master/sitl_config/mavros/install_geographiclib_datasets.sh

sudo chmod a+x ./install_geographiclib_datasets.sh

sudo ./install_geographiclib_datasets.sh 

2. Pixhawk 4 flight control serial port settings

There are two ways to connect to ROS

The first one: USB serial port and TELEM2 connection of Pixhawk 4

1. I found the interface diagram corresponding to the flight control on the PX4 official website. There are only 3 lines connected between TELEM2 and the USB serial port:
   2 (TX) → USB port (RX)
   3 (RX) → USB port (TX)
   6 (GND) → USB port ( GND)
   
   
2. After the USB serial port is connected to the computer, make sure that Ubuntu and the USB serial port are connected. If not, it may be a problem with the virtual machine. Then go to the path where you installed ROS (mine is in opt/ros/),

opt/ros/melodic/share/mavros/launch/px4.launch/

Enter px4.launch and modify the following line of code

<arg name="fcu_url" default="/dev/ttyACM0:115200" />

ttyACM0:115200Change tottyUSB0：921600

4. Power the Pixhawk 4 flight controller, then open the terminal and enter

roslaunch mavros px4.launch

Based on this error report, we give it permission

sudo chmod 777 /dev/ttyUSB0

then start again

roslaunch mavros px4.launch

Second method: Connect the USB port of Pixhawk 4 to the computer

At this time, you need to add px4.launch in the path below

opt/ros/melodic/share/mavros/launch/px4.launch/

change into

<arg name="fcu_url" default="/dev/ttyACM0:115200" />

Save and exit, open terminal, start

roslaunch mavros px4.launch

3. Test whether the Pixhawk 4 flight controller is connected to ROS

Open a new terminal

rostopic echo /mavros/local_position/pose

or

rostopic echo /mavros/local_position/velocity_body

If the information can be printed out, the connection is normal.

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