To set up the Pi and other hardware in this framework:

Option 1: Restore from image backup

• Open Ubuntu 22.04 or 24.04 on a laptop or desktop computer
• Download the image from the Google Drive /resources folder
• Insert the SD card into the computer
• Open the Disks program
• Select the SD card in the left sidebar
• Select Restore from image...
• Select the .img file you downloaded from the Drive
• Start flashing the SD card! This will take about an hour.
• Once done, eject the SD card and insert into the Pi. The RealSense and DroneKit bindings should be set up.
• If the eject fails with an obscure message about "No object for D-Bus interface", do the following:
  • sudo apt-get install gparted && gparted
  • Select the disk (likely sdb) in Gparted
  • Close Gparted and try again

Option 2: Set up from scratch [estimated time: 1-1.5 hours]

• Plug a 64 GB microSD card into your computer
• Install Ubuntu 22.04 for a Raspberry Pi 4B with the Raspberry Pi imager app
• Keep the SD attached to your computer, and open the system-boot directory
• Extend the USBfs buffer size to 2048 MB with the following step:
  • Add usbcore.usbfs_memory_mb=2048 to the cmdline.txt file in the /boot/ directory (using sd card adapter)
• Disable BT and add UART for DroneKit with the following step:
  • Add dtoverlay=disable-bt and enable_uart=1 to the config.txt file in the /boot/ directory
• Save the .txt files, eject the card, and insert it into the Pi (shiny 'pins' facing up into the PCB)
• Boot up the Pi and set it up without WiFi
• Once you're at the main desktop and logged in properly, begin setting up WiFi on the Pi
  • Using a personal computer already connected to WiFi, download the certificate from here and copy it to a USB-A type thumb drive
  • Copy the certificate from the thumb drive onto the Pi desktop
  • Go to settings, select eduroam, select Protected EAP, upload certificate, set MSCHAPv2, add your username and password
  • Username: netid@u.northwestern.edu, password: yourpassword
• Update all system programs with sudo apt-get update && sudo apt-get upgrade
• Install Python's pip module with sudo apt-get install -y python3-pip
• Install Python 3.7 with the following steps:
  • sudo add-apt-repository ppa:deadsnakes/ppa
  • sudo apt install -y python3.7 && sudo apt install -y python3.7-distutils
  • sudo update-alternatives --install /usr/bin/python python /usr/bin/python3.7 1 && sudo update-alternatives --install /usr/bin/python python /usr/bin/python3.10 2
  • sudo update-alternatives --config python and select Python 3.7
• Install openssh-server with sudo apt-get -y install openssh-server on the Pi 4
  • Once the SSH server is set up, check the IP address in Settings/WiFi and write it down for recurring use in the execution section
• Install video4linux drivers with sudo apt-get -y install v4l-utils, required to assign udev rules
• Install DroneKit with python3.7 -m pip install dronekit

If you are installing the RealSense SDK:

• Install the RealSense SDK 2.0 on the Pi 4. Follow the instructions here, taking care not to install the kernel patches (may take 1-2 hours to compile)
• Install opencv-contrib-python (includes additional libraries) with python3.7 -m pip install opencv-contrib-python
• Install the Python RealSense bindings with python3.7 -m pip install pyrealsense2

Execution

• ssh into the Pi with the following Terminal/PowerShell argument:
  • ssh -X pi@<ip_address> (replace <ip_address> with the Pi's IP address)
• Once attached to the Pi, go to the proper directory with cd operationCode/
• Set up the RealSense display with export DISPLAY=:0
• Run rs-enumerate-devices to prime the RealSense USB buffer (mysterious, please do not ask why this works)
• Run the DroneKit code OR directly run the RealSense script with python3 alignment_test.py
• Once the script is complete, end with CTRL+C
• If you want to run the control script again while the Pi is still powered, you must unplug the RealSense, wait 3-5 seconds, and rs-enumerate-devices again before execution!

Troubleshooting

• If the connection times out, unplug the RealSense camera, wait 3-5 seconds, and then replug in the other Pi USB 3.0 (blue USB) port
• The scripts will likely work if rs-enumerate-devices yields an immediate response
  • If rs-enumerate-devices hangs or takes more than 2 seconds to execute, unplug the camera and try again