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Hardware Setup

MAVROSPY is supported on a PX4 (v1.15.2) flight controller with a RPi4 (Ubuntu 22.04 MATE) or Jetson Nano (JetPack 4.6) companion computer. Additionally, it supported on ROS2 Humble and ROS1 Noetic.

PX4 allows interaction with a companion computer via OFFBOARD mode. Make sure to setup an OFFBOARD mode switch and an Emergency Kill switch in QGroundControl.

If you haven't already, please install Ubuntu MATE 22.04 for the RPi4 (arm64) or JetPack 4.6 for the Jetson Nano using the Raspberry Pi Imager.

Wiring​

This tutorial uses the flight controller's TELEM2 port to communicate with the companion computer.

Connect the flight controller's TELEM2 TX/RX pins to the complementary RXD/TXD pins on the RPi4 GPIO board:

PX4 TELEM2 PinRPi4 GPIO Pin
UART5_TX (2)RXD (GPIO 15 - pin 10)
UART5_RX (3)TXD (GPIO 14 - pin 8)

This diagram shows the RPi4 GPIO board pinout:

RPi4 Andrew Bernas

The standard TELEM2 pin assignments are shown below:

PinsSignalVoltage
1 (Red)VCC (out)+5V
2 (Black)UART5_TX (out)+3.3V
3 (Black)UART5_RX (in)+3.3V
4 (Black)UART5_CTS (out)+3.3V
5 (Black)UART5_RTS (in)+3.3V
6 (Black)GNDGND

The RPi4 requires a separate 5V/3A power supply via the 5V power (pin 4) and Ground (pin 6). I would recommend soldering a battery elimination circuit (BEC) or Polulu voltage regulator to your UAV's power leads.

PX4 Parameters​

Assuming you have installed the latest PX4 firmware, change the following parameters in QGroundControl:

   MAV_1_CONFIG = TELEM2
   UXRCE_DDS_CFG = 0
   SER_TEL2_BAUD = 921600

Setting up SSH​

SSH allows us to remotely issue commands to the companion computer over Wi-Fi.

Install the openssh-server package on your companion computer:

$ sudo apt update
$ sudo apt install -y openssh-server net-tools

The SSH service will start automatically. We can verify this by entering:

$ sudo systemctl status ssh

You should see Active: active (running) somewhere in the status report. CTRL+C to exit.

On your publishing computer, SSH to your companion computer. Make sure you change username to your companion computer's username and ip_address to your companion computer's IP address:

$ ssh username@ip_address

Remember, you can always check your IP address via:

$ ifconfig

If you forget your username, you can alway run:

$ echo $USER

We can now issue commands to our companion computer via SSH rather than having it hooked up to a monitor with a mouse and keyboard.

Enable UART (RPi4 Only)​

Open the firmware boot configuration file:

$ sudo nano /boot/firmware/config.txt

Append the following text to the end of the file (after the last line):

enable_uart=1
dtoverlay=disable-bt

Save and exit the file.

Test Connection​

MAVLink is the default and stable communication interface for working with PX4.

We can test that the companion computer and flight controller are communicating with each other via a MAVLink GCS called mavproxy.

Run this command to add your user to the dialout group:

$ sudo adduser ${USER} dialout

Restart your companion computer.

You can check that the serial port is available by issuing this command:

$ ls /dev/serial0

The result of the command should include the RX/TX connection /dev/serial0

Install MAVProxy:

$ sudo apt install -y python3-pip
$ sudo pip3 install mavproxy
$ sudo apt remove -y modemmanager

Run MAVProxy, setting the port to connect to /dev/serial0 and the baud rate to match the flight controller (921600):

$ sudo mavproxy.py --master=/dev/serial0 --baudrate 921600

MAVProxy on the RPi4 should now connect to the flight controller via its RX/TX pins. You should be able to see this in the terminal. CTRL+C to exit.

Install Docker​

Installing Docker on Ubuntu is very easy and will allow us to build the ROS environment onto the companion computer in just a few steps.

This is a summarized version of the offical installation insructions.

Setup Docker's apt repsitory:

$ sudo apt install -y ca-certificates curl
$ sudo install -m 0755 -d /etc/apt/keyrings
$ sudo curl -fsSL https://download.docker.com/linux/ubuntu/gpg -o /etc/apt/keyrings/docker.asc
$ sudo chmod a+r /etc/apt/keyrings/docker.asc
$ echo \
  "deb [arch=$(dpkg --print-architecture) signed-by=/etc/apt/keyrings/docker.asc] https://download.docker.com/linux/ubuntu \
  $(. /etc/os-release && echo "$VERSION_CODENAME") stable" | \
  sudo tee /etc/apt/sources.list.d/docker.list > /dev/null
$ sudo apt update

Install the Docker packages:

$ sudo apt install -y docker-ce docker-ce-cli containerd.io docker-buildx-plugin docker-compose-plugin

Create the docker group if not already created:

$ sudo groupadd docker

Add your user to the docker group:

$ sudo usermod -aG docker $USER

Restart so that your group membership is re-evaluated.

We can verify our Docker installation via:

$ docker run hello-world

Build MAVROSPY Docker image​

Now that Docker is installed properly, we can build our Docker image and run it in a Docker container.

Clone the mavrospy repository:

$ cd ~
$ git clone -b ros2 https://github.com/bandofpv/mavrospy.git

Build via the run_docker.sh script:

$ cd ~/mavrospy/docker/rpi
$ bash run_docker.sh

The script will automatically start building the MAVROSPY docker image and run it in a container.

CTRL+D to exit the container.