Hardware setup for the Radar Cable Follower drone

Includes the mounting mechanism, setting up the Raspberry Pi (3B+) and Pixhawk Mini (4), and validating connections.

See /CAD/ directory for files.

• Flash SD card with Ubuntu 20.04 server image.
• Increase swap to 5GB
  • dd if=/dev/zero of=<path_to_swapfile.img> bs=1024 count=5M
  • mkswap <path_to_swapfile.img>
  • Add to /etc/fstab: <path_to_swapfile.img> swap swap sw 0 0
  • swapon <path_to_swapfile.img>

Install ROS2:

• sudo apt update
• sudo apt upgrade
• sudo apt update && sudo apt install curl gnupg2 lsb-release
• sudo curl -sSL https://raw.githubusercontent.com/ros/rosdistro/master/ros.key -o /usr/share/keyrings/ros-archive-keyring.gpg
• echo "deb [arch=$(dpkg --print-architecture) signed-by=/usr/share/keyrings/ros-archive-keyring.gpg] http://packages.ros.org/ros2/ubuntu $(lsb_release -cs) main" | sudo tee /etc/apt/sources.list.d/ros2.list > /dev/null
• pip3 install pyros-genmsg
• sudo apt-get install build-essential
• sudo apt install ros-foxy-desktop
• sudo apt install python3-colcon-common-extensions
• sudo apt-get install ros-foxy-cv-bridge
• sudo apt install libpcl-dev

• cd ~
  mkdir -p ~/ros2_ws/src

Install PX4:

• Foonathan memory:

  • cd ~
  • git clone https://github.com/eProsima/foonathan_memory_vendor.git
  • cd foonathan_memory_vendor
  • mkdir build && cd build
  • cmake ..
  • sudo cmake --build . --target install

• Fast-RTPS-Gen

  • sudo apt-get install openjdk-8-jre
  • export JAVA_HOME=/usr/lib/jvm/java-8-openjdk-arm64
  • cd ~
  • git clone --recursive https://github.com/eProsima/Fast-DDS-Gen.git -b v1.0.4 ~/Fast-RTPS-Gen \ && cd ~/Fast-RTPS-Gen \ && ./gradlew assemble \ && sudo ./gradlew install

• PX4:

  • cd ~
    git clone -n https://github.com/PX4/PX4-Autopilot.git
    cd PX4-Autopilot/
    git checkout 6823cbc4140e29568f00e1211ae60e057adb1a1f
    (not needed unless for simulation) git submodule update --init --recursive
    bash ./Tools/setup/ubuntu.sh

    To listen to radio channels, edit ~/PX4-Autopilot/msg/tools/urtps_bridge_topics.yaml to include:

      - msg:     rc_channels
        send:    true

    Then run:

    cd ~/PX4-Autopilot/msg/tools/
    python3 uorb_to_ros_urtps_topics.py -i ~/PX4-Autopilot/msg/tools/urtps_bridge_topics.yaml -o ~/ros2_ws/src/px4_ros_com/templates/urtps_bridge_topics.yaml

    The PX4 firmware for the flight controller (.px4 file) must be built with the same topics in the above file. A known-to-work version has the following content:

    rtps:
      - msg:     offboard_control_mode
        receive: true
      - msg:     telemetry_status
        receive: true
      - msg:     timesync
        receive: true
        send:    true
      - msg:     vehicle_command
        receive: true
      - msg:     vehicle_control_mode
        send:    true
      - msg:     vehicle_local_position_setpoint
        receive: true
      - msg:     trajectory_setpoint # multi-topic / alias of vehicle_local_position_setpoint
        base:    vehicle_local_position_setpoint
        receive: true
      - msg:     vehicle_odometry
        send:    true
      - msg:     vehicle_status
        send:    true
      - msg:     timesync_status
        send:    true
      - msg:     rc_channels
        send:    true

  • cd ~/ros2_ws/src
    git clone -n https://github.com/PX4/px4_ros_com.git
    cd px4_ros_com/
    git checkout 1562ff30d56b7ba26e4d2436724490f900cc2375
    cd ..
    git clone -n https://github.com/PX4/px4_msgs.git
    cd px4_msgs/
    git checkout b64ef0475c1d44605688f4770899fe453d532be4

  • cd ~/PX4-Autopilot/msg/tools/
    ./uorb_to_ros_msgs.py ~/PX4-Autopilot/msg/ ~/ros2_ws/src/px4_msgs/msg/

  • This step may take more than an hour:

    cd ~/ros2_ws/src/px4_ros_com/scripts/
    ./build_ros2_workspace.bash --verbose

Radar Cable Follower and IWR6843ISK ROS2 packages installation:

• cd ~/ros2_ws/src/
• git clone https://github.com/nhma20/radar_cable_follower.git
• git clone https://github.com/nhma20/radar_cable_follower_msgs.git
• git clone https://github.com/nhma20/iwr6843isk_ros2.git
• cd ~/ros2_ws/
• colcon build

Set up SSH:

• sudo apt update
• sudo apt install openssh-server
• sudo systemctl status ssh (check if running)
• sudo ufw allow ssh

Connect to network:

• nmcli radio wifi (check if wifi on)
• nmcli dev wifi list (list available networks)
• sudo nmcli dev wifi connect <wifi_ssid> password "<password>"
• Get host ip:
  • ifconfig (look for wlan* or eth or enp or similar)
• sudo nmap -sP <host_ip>/24 | awk '/^Nmap/{ip=$NF}/B8:27:EB/{print ip}' (for Raspberry Pi 3)
• e.g.: sudo nmap -sP 192.168.1.0/24 | awk '/^Nmap/{ip=$NF}/B8:27:EB/{print ip}'
• if dnet: Failed to open.. try sudo snap connect nmap:network-control or nmap with --unprivileged flag.
• Try logging in on each output IP addres:
  • ssh ubuntu@<ip_from_above>

• Connect via USB to Host PC running QGroundControl
• On host PC:
  • Load Pixhawk with default firmware (1.12.3) through QGroundControl
  • Reset all parameters
  • Build specific version of firmware:
    • git clone -n https://github.com/PX4/PX4-Autopilot.git
    • git checkout d7a962b4269d3ca3d2dcae44da7a37177af1d8cd
    • git submodule update --init --recursive
    • Delete the micro_dds directory in the firmware (PX4-Autopilot/src/modules/microdds_client/)
    • Go to PX4-Autopilot/boards/px4/fmu-v5/rtps.px4board (create if does not exist) and set CONFIG_MODULES_MICRODDS_CLIENT=n
    • cd ~/PX4-Autopilot/
    • make px4_fmu-v5_rtps
  • Load Pixhawk with newly built firmware (~/PX4-Autopilot/build/px4_fmu-v5_rtps/px4_fmu-v5_rtps.px4) through QGroundControl
  • Set parameters (file provided in /pixhawk_parameters/ directory):
    • RTPS_CONFIG TELEM1
    • MAV_0_CONFIG TELEM/SERIAL4
    • RTPS_MAV_CONFIG Disabled
    • SER_TEL1_BAUD 460800 8N1
    • SER_TEL4_BAUD 57600 8N1 Optional speed parameters:
    • MPC_Z_VEL_ALL 3
    • MPC_XY_VEL_ALL 5
• Validate connection between Raspberry Pi and Pixhawk:
  • Connect FTDI-USB-to-Serial between Raspberry Pi USB port and Pixhawk TELEM1 port.
  • Power on Pixhawk (battery or debug micro-USB port).
  • On Raspberry Pi:
    • source ~/ros2_ws/install/setup.sh
    • micrortps_agent -d /dev/ttyUSB0 (find correct port first)
    • ros2 topic echo /fmu/vehicle_odometry/out (should print the odometry messages from the Pixhawk)
    • If there is no connection, check that the micrortps_client is running on the Pixhawk with the MAVLink Console:
      • micrortps_client status
      • debug from there