Building a map using SLAM on a Raspberry Pi

Setup personal machine to communicate wih ROS + RP4

Setup Ubuntu 20.04 Desktop on RP4

Because the latest ROS distribution (ROS Noetic Ninjemys) is not supported by Ubuntu 22.04 we will install Ubuntu 20.04.

For ROS we will install the desktop version of Ubuntu (Ubuntu 20.04 Desktop) as this will help us more with visualizing ROS.

There never was a specific desktop version of Ubuntu 20.04 for Raspberry Pi. Instead, we have to install the server version of Ubuntu 20.04, and when that is installed, install the desktop environment from the terminal.

Start with downloading Raspberry Pi Imager on your personal machine, insert your SD card and flash it with Ubuntu 20.04 Server. Insert the SD card into the RP4, connect display and HDMI cable, login (login: ubuntu, password: ubuntu), and change the password. Now install the desktop version (without all the bloat) with:

sudo apt-get update && upgrade
sudo apt-get install --no-install-recommends ubuntu-desktop

Install and setup LightDM as a Desktop Environment/GUI:

sudo apt-get install lightdm

Choose lightdm in the popup window

sudo systemctl start lightdm.service    #You are maybe forced to press ctrl+alt+F2 to come back to the terminal
sudo service ligthdm start
sudo reboot

Add below to config.txt (This need to be done in a separate file sudo nano /boot/firmware/usercfg.txt)

hdmi_drive=2
hdmi_safe=1
dtoverlay=vc4-fkms-v3d

Be aware that RP4 has 2 HDMI-outputs and some of the programs might open in HDMI1 (You should be connected to HDMI0).

Setup ROS

For RP4 we will install ROS Noetic

http://wiki.ros.org/noetic/Installation/Ubuntu

Install further packages:

sudo apt-get install python3-roslaunch
sudo apt-get install ros-noetic-rosserial && ros-noetic-rosserial-arduino

Setup PlatformIO

PlatformIO is used to upload code to arduino from the terminal

sudo apt-get install python3 python3-pip
sudo python3 -m pip install -U platformio

Setup OLED display

Install used packages

pip3 install Adafruit_GPIO
pip3 install adafruit-ssd1306
sudo apt-get install python3-dev python3-rpi.gpio

wget https://archive.raspberrypi.org/debian/pool/main/r/raspi-config/raspi-config_20200601_all.deb -P /tmp
sudo apt-get install libnewt0.52 whiptail parted triggerhappy lua5.1 alsa-utils -y
sudo apt-get install -fy
sudo dpkg -i /tmp/raspi-config_20200601_all.deb

Follow these instructions to enable I2C interface: https://www.instructables.com/Raspberry-Pi-Monitoring-System-Via-OLED-Display-Mo/

sudo chmod a+rw /dev/i2c-* is temporary a solution and is lost at next boot. To fix it permanently you need to do the following: https://lexruee.ch/setting-i2c-permissions-for-non-root-users.html

Setup RP camera

Enable camera

sudo apt-get update && upgrade

Edit /boot/firmware/config.txt, append the following config at the end of the file

start_x=1
gpu_mem=128

And comment out dtparam=i2c_arm=on

Follow these instructions to enable the RP camera v2.1: https://zengliyang.wordpress.com/2021/01/04/raspberry-pi-4b-ubuntu-20-04-camera/

curl -L --output /usr/bin/rpi-update https://raw.githubusercontent.com/Hexxeh/rpi-update/master/rpi-update && chmod +x /usr/bin/rpi-update
sudo rpi-update
sudo apt install cmake
git clone https://github.com/raspberrypi/userland.git
cd userland
./buildme # or "./buildme --aarch64" for 64-bit OS
touch ~/.bash_aliases
echo -e 'PATH=$PATH:/opt/vc/bin\nexport PATH' >> ~/.bash_aliases
echo -e 'LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/opt/vc/lib\nexport LD_LIBRARY_PATH' >> ~/.bash_aliases
source ~/.bashrc
sudo ldconfig

Give non-root users access to the camera device:

echo 'SUBSYSTEM==\"vchiq\",GROUP=\"video\",MODE=\"0660\"' > /etc/udev/rules.d/10-vchiq-permissions.rules
sudo usermod -a -G video $USER
sudo reboot

Calibrate camera

Install calibration package

Terminal 1

sudo apt-get install ros-noetic-camera-calibration
sudo apt-get install python3-rosdep
sudo rosdep init
rosdep update
rosdep install camera_calibration

cd RoboCup2023/Building-a-map-using-SLAM-on-a-Raspberry-Pi/catkin_ws/src/camera/src/
python publisher.py 

Terminal 2

rosrun camera_calibration cameracalibrator.py --size 8x6 --square 0.026 image:=/camera/image_raw camera:=/camera/image_raw --no-service-check

Setup ORB-SLAM3

OpenCV

git clone https://github.com/opencv/opencv.git
cd opencv
mkdir build && cd build
cmake -D CMAKE_BUILD_TYPE=RELEASE -D CMAKE_INSTALL_PREFIX=/usr/local -D WITH_TBB=ON -D BUILD_NEW_PYTHON_SUPPORT=ON -D WITH_V4L=ON -D INSTALL_C_EXAMPLES=ON -D INSTALL_PYTHON_EXAMPLES=ON -D BUILD_EXAMPLES=ON -D WITH_QT=ON -D WITH_GTK=ON -D WITH_OPENGL=ON ..
make -j4
sudo make install

Pangolin

git clone https://github.com/stevenlovegrove/Pangolin.git
cd Pangolin
mkdir build
cmake -B build
cmake --build build

ORB-SLAM3

git clone https://github.com/UZ-SLAMLab/ORB_SLAM3.git ORB_SLAM3
cd ORB_SLAM3
sed -i 's/++11/++14/g' CMakeLists.txt   #Change the compiler version in CMakeLists.txt from c++11 to c++14
chmod +x build.sh
./build.sh

Run ORB-SLAM3-script

cd ORB_SLAM3/
./Examples/Monocular/mono_tum Vocabulary/ORBvoc.txt ./Examples/Monocular/RP4.yaml

Run ROS ORB-SLAM3-script

Copy the folder 'ROS' Example_old to Example

Add/Edit the following CMakeLists.txt inside ORB_SLAM3/Examples/ROS/ORB_SLAM3

find_package(OpenCV 4.6 QUIET)
if(NOT OpenCV_FOUND)
   find_package(OpenCV 3.0 QUIET)
   if(NOT OpenCV_FOUND)
      find_package(OpenCV 2.4.3 QUIET)
      if(NOT OpenCV_FOUND)
         message(FATAL_ERROR "OpenCV > 2.4.3 not found.")
      endif()
   endif()
endif()

Add the following: https://github.com/nindanaoto/ORB_SLAM3/blob/ec9ea0a24b4c5e2181a912751ad01bd17d31ea46/Examples/ROS/ORB_SLAM3/CMakeLists.txt#L46

Use the following command inside ORB_SLAM3/Examples/ROS/ORB_SLAM3

sed -i 's/++11/++14/g' CMakeLists.txt

Add the following: UZ-SLAMLab/ORB_SLAM3#479 (comment)

chmod +x build_ros.sh
./build_ros.sh

Terminal 1

cd RoboCup2023/Building-a-map-using-SLAM-on-a-Raspberry-Pi/catkin_ws/src/camera/src/
python publisher.py 

Terminal 2

cd ORB_SLAM3/
rosrun ORB_SLAM3 Mono Vocabulary/ORBvoc.txt Examples/Monocular/RP4.yaml

Run ROS ORB-SLAM3 wrapper-script

clone https://github.com/thien94/orb_slam3_ros_wrapper into your catkin-folder

Terminal 1

roslaunch orb_slam3_ros_wrapper euroc_mono.launch

Terminal 2

rosbag play MH_01_easy.bag

SSH

SSH onto RP4

ssh -X ubuntu@185.107.14.82

-X starts up a proxy X11 server on the remote machine.

When ssh-ing with GUI from a windows computer follow these steps:

• Launch XMing on Windows client
• Launch Putty
  • Fill in basic options as you know in session category
  • Connection -> SSH -> X11 -> Enable X11 forwarding -> X display location = :0.0 -> MIT-Magic-Cookie-1 -> X authority file for local display = point to the Xming.exe executable

SSH folder from RP onto personal computer

Create folder (e.g. RP4_files)

sshfs ubuntu@185.107.14.82:/ /home/magnus/RP4_files/

SSH in Visual Studio Code

SSH onto RP4 via VSC

• Open VSC

• Click on green box ('Open a Remote Window') in lower left corner (If this can't be found, be sure that Remote - SSH is installed from Extensions)

• Click 'Connect to Host...'

• ubuntu@185.107.14.82

Source .bash-file

Every terminal should source it automatically, if not you may do it manually

source /home/ubuntu/RoboCup2023/Building-a-map-using-SLAM-on-a-Raspberry-Pi/catkin_ws/devel/setup.bash

Source .bash-file automatically

1. nano ~/.bashrc

2. Go to the bottom (last line should be something like source /opt/ros/noetic/setup.bash)

3. Go under that line and write source /home/ubuntu/RoboCup2023/Building-a-map-using-SLAM-on-a-Raspberry-Pi/catkin_ws/devel/setup.bash

4. Save and exit

5. source ~/.bashrc

Now with every new shell you open, it will source automatically

Start using ROS

Upload Arduino-code from terminal

Using platformio to send code to Arduino

cd RoboCup2023/Building-a-map-using-SLAM-on-a-Raspberry-Pi/arduino/

Arduino Mega 2560

pio run -e megaatmega2560 -t upload

Create a ROS package

Follow http://wiki.ros.org/ROS/Tutorials/CreatingPackage

Create script to launch at Boot

Follow https://roboticsbackend.com/make-ros-launch-start-on-boot-with-robot_upstart/

sudo apt-get install ros-noetic-robot-upstart 

Install script to launch at boot

cd RoboCup2023/Building-a-map-using-SLAM-on-a-Raspberry-Pi/catkin_ws/src/
rosrun robot_upstart install ros_setup/launch/ros_setup.launch --job ros_setup --symlink
sudo systemctl daemon-reload 

Disabling

sudo systemctl disable OLEDDisplay.py.service

Re-enable

sudo systemctl enable OLEDDisplay.py.service

Kill all ROS nodes

rosnode kill --all

Communication (Subscriber and publisher)

Publisher

Command	Data types	Action	Publish frequency [s]
/battery/voltage	Float32MultiArray	Give the voltage of the battery for the motors and RP	2 (if the value differs)
/camera/image_raw	Image	Image from Raspberry Pi camera. Test with: sudo apt-get install ros-noetic-rqt-image-view && rqt_image_view	0.1
/IMU/orientation	Int16MultiArray	Give the orientation in degrees [pitch, roll, yaw]	0.25
/IMU/temperature	Float32	Give the temperature (from the MPU6050-chip)	2 (if the alue differs)
/joystick	String	Give pressed and released keys and values from the joystick
/motor/encoderTick	Int16MultiArray	Give the encoder ticks for the two wheels [L, R]	0.1 (if the value differs)
/motor/odom	Odometry	Give the odometry of the robot (position, orientation, and linear- and angular velocity)	0.25
/move_base_simple/goal	PoseStamped	Give the position and orientation of the desired location
/tf	TFMessage	Give the odometry of the robot (position, orientation)	0.25

Subscriber

Command	Data types	Action	Example
/IMU/CmdCaliIMU	Empty	Calibrate the IMU	rostopic pub /IMU/CmdCaliIMU std_msgs/Empty
/motor/CmdResetOdom	Empty	Reset the odometry	rostopic pub /motor/CmdResetOdom std_msgs/Empty
/motor/CmdSetEvent	String	Set an event, when to stop the motors	rostopic pub /motor/CmdSetEvent std_msgs/String dist=1.2 (drive 1.2m).
/motor/CmdSetTurnRadius	Float32	Set the turning radius [m]. O.B.S. set first velocity.	rostopic pub /motor/CmdSetTurnRadius std_msgs/Float32 0.4 (set the turning radius to 0.4 m). Setting the turning radius to 0 will have the robot to spin around its center
/motor/CmdSetVelocity	Float32	Set the velocity of both motors [m/s]	rostopic pub /motor/CmdSetVelocity std_msgs/Float32 1.2 (set the overall wheel velocity to 1.2 m/s). Use -- before negativ values (e.g. -- -4).
/motor/CmdSetVelocityPWM	Int16MultiArray	Set the velocity of both motors (0 = off and 255 = max speed). Negative values will drive the motor backwards
/OLED/CmdSetText	String	Write 1 line of text to one of the 8 lines on the OLED display. Line 1-5 are reserved for IP-address, CPU Load, Memory, Disk and Voltage. The display updates every 1 sec	rostopic pub /OLED/CmdSetText std_msgs/String 6_Robot (writes Robot to line 6). Use " when writing multiple words.

Other

Shutdown RP

Don't just pull the plug. Use instead:

sudo shutdown -h now

LiDAR

cd ~/RoboCup2023/Building-a-map-using-SLAM-on-a-Raspberry-Pi/
roslaunch mb_1r2t_ros view.launch port:=/dev/ttyUSB1

If ttyUSB1 can't be found look for the USB-device with ls /dev/tty*

This will open RViz and show the LiDAR data

Control power to RP4 USB-ports

https://github.com/mvp/uhubctl#raspberry-pi-b2b3b

Microcontroller

Minimum requirements:

• Ports
  • Digital input (interrupt): 4
  • Digital output (PWM): 6
  • Analog input: 2
  • I2C: 1
• Storage
  • RAM: 3 kB (2837 B)
  • Flash: 23 kB (22674 B)

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