Matek ~~~ RPi4
Rx7 ==> GPIO 14 (Pin 8)
Tx7 ==> GPIO 15 (Pin 10)
Rts7 ==> GPIO 16 (Pin 36)
Cts7 ==> GPIO 17 (Pin 11)
Gnd ==> Gnd
Flash SD card with Ubuntu 22.04 LTS (64 bit) using Raspberry Pi Imager. This guide should work for both Desktop or Server versions of Ubuntu, but if you're going Server, it would be best to configure your networking before going too far in the setup process, to allow yourself to ssh into the RPi4 and copy/paste the commands from a PC with a web explorer.
sudo update
sudo rpi-eeprom-update -a
sudo reboot
sudo apt update
sudo apt upgrade -y
sudo reboot
Edit sudo nano /boot/firmware/config.txt. At the bottom of the file, add the lines:
enable_uart=1
init_uart_clock=200000000
dtoverlay=disable-bt
dtoverlay=uart0,ctsrts
gpio=16-17=a3
Explanation: RPi 4 has 2 types of UART
- PL011 (better)
- Mini-UART (reduced features)
We disable Bluetooth (which was on a PL011) to move the primary UART from a Mini-UART to the PL011 (more info here). We also specify that UART0 will use hardware flow control (ctsrts) using GPIO 16 and 17. And we speed up the UART clock to 200 MHz to allow for a 12.5 MBaud connection. UART0 will be available on /dev/ttyAMA0 or /dev/serial0.
Then save /boot/firmware/config.txt with these changes.
To make sure the Primary UART (UART0) is unoccupied, disable the Bluetooth controller and the serial Linux console permanently.
sudo systemctl disable hciuart
sudo systemctl disable serial-getty@ttyAMA0.service
To make sure to disable the serial Linux console, edit the file
sudo nano /boot/firmware/cmdline.txt
Remove the console=serial0,115200 or similar entry, leaving the rest of the line intact.
And then add yourself into the group dialout to be allowed to use the UART ports
sudo usermod -a -G dialout $USER
sudo reboot
Optional: CPU overclock
For those who need a little extra from the CPU. You can add these lines to /boot/firmware/config.txt. Choose either of the 2 sets of 3 parameters.
#over_voltage=6
#arm_freq=2000
#gpu_freq=700
over_voltage=8
arm_freq=2250
gpu_freq=750
This will not improve DDS or PPP. It's only in case you plan on running CPU intensive algorithms alongside DDS.
Issue where the "Wait for network" service unnecessarily making the boot long
sudo systemctl edit systemd-networkd-wait-online
Add this under the first two commented lines
[Service]
ExecStart=
ExecStart=/lib/systemd/systemd-networkd-wait-online --timeout=10 --interface=wlan0
Then
sudo systemctl daemon-reload
sudo systemctl restart systemd-networkd-wait-online
sudo reboot
Install the Ardupilot development environment (more info here).
sudo apt install git -y
git clone --recurse-submodules https://github.com/ArduPilot/ardupilot.git
cd ardupilot
Tools/environment_install/install-prereqs-ubuntu.sh -y
. ~/.profile
sudo reboot
Install ROS 2 Humble (more info here).
Make sure your locales are set to UTF-8
locale # check for UTF-8
sudo apt update && sudo apt install locales
sudo locale-gen en_US en_US.UTF-8
sudo update-locale LC_ALL=en_US.UTF-8 LANG=en_US.UTF-8
export LANG=en_US.UTF-8
locale # verify settings
Setup the sources for apt
sudo apt install software-properties-common
sudo add-apt-repository universe
sudo apt update && sudo apt install curl -y
sudo curl -sSL https://raw.githubusercontent.com/ros/rosdistro/master/ros.key -o /usr/share/keyrings/ros-archive-keyring.gpg
echo "deb [arch=$(dpkg --print-architecture) signed-by=/usr/share/keyrings/ros-archive-keyring.gpg] http://packages.ros.org/ros2/ubuntu $(. /etc/os-release && echo $UBUNTU_CODENAME) main" | sudo tee /etc/apt/sources.list.d/ros2.list > /dev/null
Install ROS 2 Humble
sudo apt update && sudo apt upgrade -y
sudo apt install ros-humble-ros-base ros-dev-tools -y
sudo apt install ros-humble-geographic-msgs -y
Finally, permanently source the ROS location in your shell startup script.
echo "source /opt/ros/humble/setup.bash" >> ~/.bashrc
sudo reboot
Use these steps to download the ROS 2 repos for Ardupilot DDS and install the dependencies. Based off these guides (wiki, git readme).
mkdir -p ~/ros2_ws/src && cd ~/ros2_ws/src
wget https://raw.githubusercontent.com/ArduPilot/ardupilot/master/Tools/ros2/ros2.repos
vcs import --recursive < ros2.repos
cd ~/ros2_ws
sudo apt update
sudo rosdep init
rosdep update
rosdep install --rosdistro humble --from-paths src --ignore-src
Install Micro-XRCE-DDS-Gen. This is needed when building the Ardupilot firmware with DDS enabled.
sudo apt install default-jre -y
git clone --recurse-submodules https://github.com/ardupilot/Micro-XRCE-DDS-Gen.git
cd Micro-XRCE-DDS-Gen/
./gradlew assemble
echo "export PATH=\$PATH:$PWD/scripts" >> ~/.bashrc
sudo reboot
Now is time to build the ROS 2 packages using colcon. You have 2 options for building: either you build only for a companion computer that will not be used for SITL, or you build for a computer on which you might use SITL. Most likely, you will not be using your RPi4 for SITL.
Companion computer without SITL packages
cd ~/ros2_ws
colcon build --packages-select micro_ros_agent
Building for SITL and communication with hardware
cd ~/ros2_ws
colcon build --packages-up-to ardupilot_dds_tests
The latter option will take a lot more time to build on a RPi4.
To enable the use of pppd (which is what is used on the Pi to enable the PPP connection with the flight controller), run this command
sudo apt install linux-modules-extra-raspi
sudo reboot
Most likely, the version by default on your Ubuntu 22.04 is version 2.4.9 (you can check with pppd --version. While you can still use version 2.4.9, it will not be able to achieve the fastest 12.5M baudrate. You will need version 2.5.1.
sudo apt update && sudo apt install build-essential -y
curl -L https://github.com/ppp-project/ppp/archive/refs/tags/ppp-2.5.1.tar.gz | tar -xz
cd ~/ppp-ppp-2.5.1
autoreconf -i
./configure
make
sudo make install
Andrew Tridgell has a video showcasing the uses of PPP.
If using a brand new flight controller that doesn't have Ardupilot pre-installed, you have to flash Ardupilot with bootloader. I recommend using STM32CubeProgrammer. This step doesn't have to be performed on the RPi 4, I prefer using a Windows PC. Download the latest or stable firmware for your board (for example, for the Matek H743, from here). Make sure you download the _with_bl.hex file. Then follow this guide or this video tutorial.
Once your flight controller is ready, plug it via USB to your RPi 4. Now back on your RPi 4, build the Ardupilot firmware with DDS and PPP enabled and upload it to your FC. When doing ./waf configure, specify the correct board.
cd ~/ardupilot
./waf configure --board MatekH743 --enable-dds --enable-PPP
./waf copter --upload
This will take some time.
Now you must set the correct parameters in Ardupilot. You will have to reboot and/or refresh the parameters multiples times, as you will be enabling multiple "enable" parameters. You can use Mavproxy on your RPi4 to edit the parameters (mavproxy.py --console will detect the flight controller connected via USB), or connect your flight controller to a PC with Mission Planner.
SERIAL1_PROTOCOL,48
SERIAL1_BAUD,12500000
BRD_SER1_RTSCTS,1
This enable PPP on SERIAL1, maxes out the baudrate (allowing for fast networking and fast log download using the webserver (faster than USB)), and also enables flow control.
NET_ENABLE,1
NET_OPTIONS,0
NET_P1_IP0,192
NET_P1_IP1,168
NET_P1_IP2,13
NET_P1_IP3,16
NET_P1_PORT,15001
NET_P1_PROTOCOL,2
NET_P1_TYPE,1
NET_P2_TYPE,0
NET_P3_TYPE,0
NET_P4_TYPE,0
This enables Mavlink over PPP. NET_P1_TYPE,1 sets the port to use UDP and enables the IP address parameters. The address 192.168.13.16 is the destination address, which will need to be specified by pppd on the RPi4. You can choose a random value for NET_P1_IP3, as long as it is not the same as another device on your network.
DDS_DOMAIN_ID,0
DDS_ENABLE,1
DDS_IP0,192
DDS_IP1,168
DDS_IP2,13
DDS_IP3,16
DDS_UDP_PORT,2019
This sets the DDS destination to the same address at the one specified by the NET_* parameters, but to port 2019 instead.
The webserver is done via a lua script. Therefore, first enable scripting:
SCR_ENABLE,1
SCR_VM_I_COUNT,1000000
And then download the file net_webserver.lua from Ardupilot's Github. There is also a readme. Andrew Tridgell has a good video tutorial for the webserver.
Using Mission Planner's MAVftp tool, upload the net_webserver.lua file to the flight controller's APM/scripts/ folder. Then reboot and change the following parameters:
WEB_ENABLE,1
WEB_BIND_PORT,80
You're now ready to use DDS and PPP! Power the RPi4 and the flight controller, open a terminal and run:
sudo pppd /dev/ttyAMA0 12500000 192.168.13.16:192.168.13.65 crtscts debug noauth nodetach local proxyarp ktune
This takes the incoming stream from /dev/ttyAMA0 (at a 12.5M Baudrate) destined for 192.168.13.16 (the local IP of pppd) and defines the remote (the flight controller) as 192.168.13.65. You can change 65 for anything you want.
Then, open another terminal and start the micro_ros_agent, listening on port 2019 (specified in the DDS_* parameters).
cd ~/ros2_ws
source install/setup.bash
ros2 run micro_ros_agent micro_ros_agent udp4 --port 2019
Nothing will happen at first. This is because DDS on the flight controller will shutdown if it doesn't connect to the micro_ros_agent within 10 seconds of boot. You have to reboot the flight controller. Either power cycle the flight controller, or open another terminal to connect to the flight controller using Mavlink over the PPP connection:
mavproxy.py --console --master=udp:192.168.13.16:15001
Send the command reboot to reboot your flight controller.
You should see the micro_ros_agent acknowledge the reception of the DDS topics.
You can now view the available topics with
ros2 topic list -v
Published topics:
* /ap/airspeed [geometry_msgs/msg/Vector3] 1 publisher
* /ap/battery [sensor_msgs/msg/BatteryState] 1 publisher
* /ap/clock [rosgraph_msgs/msg/Clock] 1 publisher
* /ap/geopose/filtered [geographic_msgs/msg/GeoPoseStamped] 1 publisher
* /ap/gps_global_origin/filtered [geographic_msgs/msg/GeoPointStamped] 1 publisher
* /ap/imu/experimental/data [sensor_msgs/msg/Imu] 1 publisher
* /ap/navsat [sensor_msgs/msg/NavSatFix] 1 publisher
* /ap/pose/filtered [geometry_msgs/msg/PoseStamped] 1 publisher
* /ap/tf_static [tf2_msgs/msg/TFMessage] 1 publisher
* /ap/time [builtin_interfaces/msg/Time] 1 publisher
* /ap/twist/filtered [geometry_msgs/msg/TwistStamped] 1 publisher
* /parameter_events [rcl_interfaces/msg/ParameterEvent] 1 publisher
* /rosout [rcl_interfaces/msg/Log] 1 publisher
Subscribed topics:
* /ap/cmd_gps_pose [ardupilot_msgs/msg/GlobalPosition] 1 subscriber
* /ap/cmd_vel [geometry_msgs/msg/TwistStamped] 1 subscriber
* /ap/joy [sensor_msgs/msg/Joy] 1 subscriber
* /ap/tf [tf2_msgs/msg/TFMessage] 1 subscriber
View the frequency of a topic with
ros2 topic hz /ap/time
View the contents of a topic with
ros2 topic echo /ap/imu/experimental/data
cd ~/ardupilot
git pull --recurse-submodules
cd ~/ros2_ws/Micro-XRCE-DDS-Gen
git pull --recurse-submodules
cd ~/ros2_ws
vcs custom --args remote update
vcs import src < src/ros2.repos --recursive
vcs pull src
if dependencies have changed
rosdep update
rosdep install --rosdistro humble --from-paths src --ignore-src
colcon build --packages-select micro_ros_agent
sudo apt update
sudo apt install openssh-server
sudo systemctl enable ssh
sudo systemctl start ssh
Check RPi IP address
hostname -I
Edit /etc/sysctl.conf and uncomment
net.ipv4.ip_forward=1
Create routing tables
sudo iptables -t nat -A PREROUTING -p tcp --dport 80 -j DNAT --to-destination 192.168.13.65:80
sudo iptables -t nat -A POSTROUTING -d 192.168.13.65 -j MASQUERADE
Use iptables-persistent to keep routing permanent between reboots
sudo apt install iptables-persistent
sudo netfilter-persistent save
Create pppd parameter file
sudo nano /etc/ppp/ip_config.txt
And add
# /etc/ppp/ip_config.txt
LOCAL_IP=192.168.13.16
REMOTE_IP=192.168.13.65
BAUD=12500000
Create shell script that runs pppd
sudo nano /usr/local/bin/start_pppd.sh
And add
#!/bin/bash
# Read the IPs from the configuration file
source /etc/ppp/ip_config.txt
# Start pppd with the IPs
# (pppd is in /usr/local/sbin/ if 2.5.1 manually compiled, otherwise in /usr/sbin/)
/usr/local/sbin/pppd /dev/ttyAMA0 $BAUD $LOCAL_IP:$REMOTE_IP crtscts debug noauth nodetach local proxyarp ktune
Make it executable
sudo chmod +x /usr/local/bin/start_pppd.sh
Make pppd service file
sudo nano /etc/systemd/system/pppd.service
And add
[Unit]
Description=PPP Daemon Service
After=network.target
[Service]
Type=simple
ExecStart=/usr/local/bin/start_pppd.sh
ExecStop=/bin/kill $MAINPID
Restart=on-failure
RestartSec=5s
[Install]
WantedBy=multi-user.target
Enable and start service
sudo systemctl daemon-reload
sudo systemctl enable pppd.service
sudo systemctl start pppd.service
Other commands:
sudo systemctl status pppd.service
sudo systemctl restart pppd.service
sudo systemctl stop pppd.service
sudo systemctl disable pppd.service
sudo apt install network-manager
sudo nmcli connection add type wifi ifname "*" con-name MDTK_RPI ssid MDTK_RPI
sudo nmcli connection modify MDTK_RPI wifi-sec.key-mgmt wpa-psk wifi-sec.psk "17B74|q1*gg"
sudo nmcli connection modify MDTK_RPI connection.autoconnect yes
sudo nmcli connection modify MDTK_RPI connection.autoconnect-priority 10
sudo nmcli connection modify MDTK_RPI ipv4.addresses 192.168.137.100/24
sudo nmcli connection modify MDTK_RPI ipv4.gateway 192.168.137.1
sudo nmcli connection modify MDTK_RPI ipv4.dns 8.8.8.8
sudo nmcli connection modify MDTK_RPI ipv4.method manual
nmcli connection show MDTK_RPI
Edit sudo nano /etc/netplan/*.yaml and change to renderer: NetworkManager. Then
sudo netplan apply
Create shell script
sudo nano /usr/local/bin/preferred_wifi_switch.sh
And add
#!/bin/bash
# Define the preferred Wi-Fi network
PREFERRED="MDTK_RPI"
DEBUG=true
dbg() {
if [ "$DEBUG" = true ]; then
echo "$1"
fi
}
while true; do
# Get the name of the currently active connection
CURRENT=$(nmcli -g NAME con show --active)
# Check if the current network is not the preferred network
if [ "$CURRENT" != "$PREFERRED" ]; then
dbg "Currently connected to $CURRENT"
# Check if the preferred network is available
if nmcli -g SSID device wifi list | grep -Fqwx "$PREFERRED"; then
dbg "Attempting switch to $PREFERRED"
nmcli c up "$PREFERRED"
fi
fi
# Wait 20 seconds before checking again
sleep 20
done
Make it executable
sudo chmod +x /usr/local/bin/preferred_wifi_switch.sh
Create service file
sudo nano /etc/systemd/system/wifi-switch.service
And add
[Unit]
Description=Wi-Fi Auto Switch Service
After=network.target
[Service]
ExecStart=/usr/local/bin/preferred_wifi_switch.sh
Restart=always
RestartSec=5
[Install]
WantedBy=multi-user.target
sudo systemctl enable wifi-switch.service
sudo systemctl start wifi-switch.service
ssh-keygen -t ed25519 -C "john.bobzwik@gmail.com"
eval "$(ssh-agent -s)"
ssh-add ~/.ssh/id_ed25519
Then copy output of
cat ~/.ssh/id_ed25519.pub
cd ~/ros2_ws/src
git clone git@github.com:bobzwik/cpp_imu_sub.git
cd ~/ros2_ws
colcon build --packages-select cpp_imu_sub
If testing with LED, follow instructions here: https://github.com/bobzwik/cpp_imu_sub/blob/main/README.md