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Raspberry Pi and Quadrotor Integration

The following documentation gives a detailed walk through on how to set up a new Raspberry Pi to control a quadrotor with PX4 autopilot.

Important Information

  • username: magicc
  • password: magicc
  • hostname: raspberrypi.local
  • ssh command with custom username: 
    ssh magicc@<IP address>
  • wifi: MAGICC
  • Dynamic IP address: 192.168.1.12 
    ssh magicc@192.168.1.12

Set Up the Raspberry Pi

Starting requirements: A new Raspberry Pi Compute Module, an IO Board, a small jumper, a micro-USB cable, and a 12V power cable.

End objective: Raspberry Pi running ROS2 on Ubuntu.

If you get stuck on steps 1 or 2 refer to this tutorial for help: How to flash Raspberry Pi OS onto the Compute Module 4 eMMC with usbboot | Jeff Geerling

1. Prepare to flash OS onto Raspberry Pi

The Raspberry Pi Compute Module 4 used in these instructions has a built in eMMC instead of an SD memory card slot. If your Raspberry Pi requires an SD card, you will download the OS directly onto that and skip to step 3. Otherwise follow these steps to flash an OS onto the eMMC:

  • Put the small jumper on the IO board. Looking straight down onto the board, it goes in a space at the top left. The location of the two pins is labelled with Fit jumper to disable eMMC Boot. This will disable the eMMC boot and instead allow you to flash an OS onto it.
  • Plug a USB cable from your computer into the IO board at the space labeled USB Slave and connect the board to power. You should see the D1 red light turn on.
  • Download usbboot
  • With the board still powered on and connected to your computer, run the rpiboot executable found in the directory of usbboot.

Success

If everything worked correctly, the eMMC storage now behaves just like a microSD card or USB drive that you plugged into your computer.

2. Flash OS onto Raspberry Pi

We will use an application called Raspberry Pi imager to flash an OS to the eMMC.

  • Download and open Raspberry Pi Imager
  • Click Choose OS > scroll down > select:
    • Other general-purpose OS > Ubuntu > Ubuntu Server 22.04.4 LTS (64-bit) for Raspberry Pi
  • Click Choose Storage and select the newly mounted eMMC.
  • Before writing, click the gear icon (Advanced options) for first-boot config:
    • Enable SSH: Choose password or SSH key
    • Set hostname (optional)
    • Set Wi-Fi (skip if using Ethernet)
  • Click Save, then Write to flash Ubuntu onto the eMMC.
  • Disconnect the RPi from your computer and power source and remove the jumper from the pins on the Compute Module IO Board.
  • Connect the RPi to power and it will boot up using the OS on the eMMC.

3. Connect to RPi via SSH

We will use a computer to remotely ssh into the RPi over Wi-Fi.

  • Make sure the RPi is powered on and connected to the same network as your computer.
  • From your own machine, run: 
    ping raspberrypi.local
  • Once you’ve found the IP address of the Pi, then run: 
    ssh pi@<IP_ADDRESS>
  • The default password is raspberry
  • If you set a custom user and password using Raspberry Pi Imager, you will instead run the following and enter your password when prompted. 
    ssh <user>@<IP_ADDRESS>

4. Install ROS2-jazzy on the RPi

Follow the documentation to install ROS2 on Ubuntu: Ubuntu (deb packages) — ROS 2 Documentation: Jazzy documentation

Note

You probably don’t need all the GUI tools on the RPi that come with the Desktop install and you can just perform the ROS-Base install.

  • Test if ROS is working by running the following in the RPi ssh terminal. 
    ros2 -h
  • Don’t forget to add the following lines to your bash file to source your environment. Doing this will automatically source the environment every time you open a new terminal: 
    source /opt/ros/jazzy/setup.bash 
source install/setup.bash

ROS Communication Between RPi and Computer

Starting requirements: Both a Raspberry Pi and a computer with ROS2.

End objective: ROS communication between the RPi and computer.

There are multiple ways to run ROS on your computer. The most straightforward way is to run ROS natively in a Linux environment. This will automatically allow network communication between ROS nodes on different devices. Just be sure to set the following variables to the same values on the computer and RPi: 

export ROS_DOMAIN_ID=0 
export ROS_AUTOMATIC_DISCOVERY_RANGE=SUBNET
Here are some other options if you don’t have a Linux environment:

  • Dual boot
  • A VM
  • Distrobox with Docker or Podman
  • Docker container in WSL

On my Windows laptop, I used Distrobox with Podman in my WSL with mirrored network mode enabled. This worked for me.

To do this, first install Linux on Windows with WSL and turn on mirrored network mode. Then navigate to the Installation section in the Distrobox documentation and follow the given steps to install Distrobox.

Send ROS Commands from RPi to PX4

Use the following guide to set up the RPi as a companion computer to Pixhawk:

Raspberry Pi Companion with Pixhawk

This can easily be adapted for other flight controllers running PX4.

Tips/Quick Reference

Don’t forget to source the ROS 2 environment: 

source /opt/ros/jazzy/setup.bash 
source install/setup.bash

Check status of client: 

uxrce_dds_client status

If the client has not started for PX4, you can start it manually (in the PX4 terminal): 

uxrce_dds_client start -t serial -d /dev/ttyS3 -b 921600

Start the agent on the RPi: 

sudo MicroXRCEAgent serial --dev /dev/serial0 -b 921600

Or try: 

sudo MicroXRCEAgent serial --dev /dev/ttyAMA0 -b 921600

To source mavlink virtual environment: 

source ~/mavproxy_venv/bin/activate

Terminal Multiplexer - tmux

It is very helpful to install a terminal multiplexer on the RPi. Use the following commands to install tmux: 

sudo apt update  
sudo apt install tmux
For quick reference, use this tmux cheatsheet. If you're completely new with tmux, check out A Quick and Easy Guide to tmux.

Cross Compiling

It can be beneficial to set up cross compiling on a computer so that you don’t have to wait hours for code to compile on the Raspberry Pi. For reference, it took 30 minutes to build the ROS package px4_msgs on the RPi but on a computer it takes 1-3 minutes.

The cross_compile tool is no longer supported in ROS.

Check out this possible alternative

Extra Guides

Guide for setting up RPi as a companion computer. Link

Raspberry Pi 4 pinout diagram (pg 17). Link

Pixhawk 6c mini pinout guide. Link

Guide for uXRCE-DDS (PX4-ROS 2/DDS Bridge). Link

ROS2 with PX4. Link

Translation node information. Link

Jaeyoung Lim’s px4-offboard example. Link

Adapted SITL and HITL code. Link

Pixracer Pro information. Link

MoCap stuff. Link