First steps

Microcontroller Configuration

For uploading the microcontroller firmware please refer to andino_firmware.

Single Board Computer (SBC)

The SBC used in this project is a Raspberry Pi 4b so the guidelines here will refer particularly to this family of on-board computers, however extending its use to other families is possible as well.

Operative System

Ubuntu Mate 22.04 ARM64 is the recommended operative system for this project. This OS provides good capabilities for an educational platform as well as good performance.

For installing this OS in the Raspberry:

  1. Download the image from here: ubuntu mate download

  2. Install OS to a microSD card using Raspberry Pi Imager. - No extra configuration should be necessary.

  3. Boot your raspberry using the microSD and a HDMI connection. Some initial configuration is necessary. Follow the wizard for a proper set up. It is recommended to use simple User and Password combinations for the user. For example:

    • user: pi

    • password: admin

  4. Once done, run sudo apt update && sudo apt upgrade in a terminal for updating the system. Then reboot.

Installing dependencies

Some packages are necessary to be installed towards a correct set up of the robot’s on-board computer.

ssh-server

In general, you will want to access the Raspberry remotely via ssh connection while being connected in the same network. So we need to install ssh-server and enable it if it is not enabled yet:

sudo apt-get install openssh-server
sudo systemctl enable ssh --now

After this you will be able to access this device from a remote computer by doing:

ssh <user>@<ip>

For example if the user is pi and the ip is 192.168.0.102

ssh pi@192.168.0.102

Common utilities

Install some common utilities that will be required later on.

sudo apt update
sudo apt install git net-tools software-properties-common build-essential -y
sudo apt install python3-rosdep2 python3-catkin-pkg python3-catkin-pkg-modules python3-rospkg-modules python3-rospkg  -y

Install ROS

Follow these instructions to install the following dependencies from binaries:

To automatically source ROS installation, it is recommended to add the following line to your ~/.bashrc file:

source /opt/ros/humble/setup.bash

Arduino

Arduino drivers are necessary for the SBC (Raspberry) <–> Microcontroller(Arduino) serial communication.

sudo apt install arduino

Configure it properly: 1. Add user to dialout and plugdev groups:

sudo usermod -a -G dialout $USER
sudo usermod -a -G plugdev $USER

Note you will need a reboot after this to be effective.

  1. Remove brltty from the system:

    sudo apt remove brltty

    In Ubuntu 22.04, there seems to be an issue with some chip drivers and the brltty daemon. To avoid this conflict, remove brltty as suggested. See this stackoverflow post for further information.

Raspberry Camera Module V2

After connecting the camera module to the Raspberry’s camera port:

sudo apt install libraspberrypi-bin v4l-utils
sudo usermod -aG video $USER

Check camera status:

vcgencmd get_camera

If the output of the previous command is supported=1 detected=1, everything is fine. If not, your camera won’t work correctly, and you need to perform some configuration first.

Modify the config.txt file for the boot:

sudo nano /boot/firmware/config.txt

And add these lines:

# Autoload overlays for any recognized cameras or displays that are attached
# to the CSI/DSI ports. Please note this is for libcamera support, *not* for
# the legacy camera stack
start_x=1
gpu_mem=128

Save and close the file. Then we need to enable the camera support for the Raspberry:

sudo raspi-config

Go to Interface Options, select camera and enable it.

Finally, you just need to reboot and the camera should be working fine.

RPLidar installation

The installation of the A1M8 RPLidar sensor is quite straightforward, and a ROS integration package will be installed later on via rosdep.

For now, after connecting it to the USB port:

  1. Verify USB connection: Green light in the USB converter (A1M8 side board) should be turned on.

  2. Check the authority of RPLidar’s serial-port: - Execute the following command to list available serial ports:

    ls -l /dev | grep ttyUSB

    • Add extra permissions by running:

    sudo chmod 666 /dev/ttyUSB<number_of_device>

USB Port name configuration

Fixed USB port names

As having multiple USB devices connected to the USB ports of the Raspberry Pi, the automatically assigned USB port numbers could unexpectedly change after a reboot. To avoid assigning your device to a tty_USBX number that isn’t the correct onew we should assign fixed USB port name for each connected device.

The idea is to be able to generate a link between the real tty_USBX port and an invented one. For this we will need to create rules, that every time the Raspberry Pi boots are executed, and therefore we always point to the correct port name.

In order to create fixed names for the USB devices follow the instructions:

  1. Check the devices you have connected:

    sudo dmesg | grep ttyUSB

    Expected output is something like the following:

    [  10.016170] usb 1-1.2: ch341-uart converter now attached to ttyUSB0
[ 309.186487] usb 1-1.1: cp210x converter now attached to ttyUSB1

    In the setup where this was tested we have:

    -> Arduino Microcontroller -> _usb 1-1.2: ch341-uart converter now attached to ttyUSB0 -> A1M8 Lidar Scanner -> _usb 1-1.1: cp210x converter now attached to ttyUSB1

    Note: If you don’t know how to identify each one you can simply connect them one by one and check this output.

  2. Look for attributes for each device that we will use to anchor a particular device with a name.

    We will use the idProduct and idVendor of each device.

    • Arduino Microcontroller:

      udevadm info --name=/dev/ttyUSB0 --attribute-walk

      You should look for the idProduct and idVendor under the category that matches the usb number(1-1.X): In this case the ttyUSB0 was referenced to the usb 1-1.2, so go to that section and find the ids:

      ATTRS{idProduct}=="7523"
ATTRS{idVendor}=="1a86"

    • Lidar Scanner

      udevadm info --name=/dev/ttyUSB1 --attribute-walk

      In this case the ttyUSB0 was referenced to the usb 1-1.1, so go to that section and find the ids:

      ATTRS{idProduct}=="ea60"
ATTRS{idVendor}=="10c4"

  3. Create the rules:

    Open the file:

    sudo nano /etc/udev/rules.d/10-usb-serial.rules

    Add the following:

    SUBSYSTEM=="tty", ATTRS{idProduct}=="7523", ATTRS{idVendor}=="1a86", SYMLINK+="ttyUSB_ARDUINO"
SUBSYSTEM=="tty", ATTRS{idProduct}=="ea60", ATTRS{idVendor}=="10c4", SYMLINK+="ttyUSB_LIDAR"

    Note that in the symlink field a fixed name is indicated.

  4. Re-trigger the device manager:

    sudo udevadm trigger

  5. Verify

    ls -l /dev/ttyUSB*

    The output should be something like the following:

    crw-rw---- 1 root dialout 188, 0 Sep  2 15:09 /dev/ttyUSB0
crw-rw---- 1 root dialout 188, 1 Sep  2 15:09 /dev/ttyUSB1
lrwxrwxrwx 1 root root         7 Sep  2 15:09 /dev/ttyUSB_ARDUINO -> ttyUSB0
lrwxrwxrwx 1 root root         7 Sep  2 15:09 /dev/ttyUSB_LIDAR -> ttyUSB1

Done! You can always use your devices by the fixed names without using the port number. Here, ttyUSB_ARDUINO and ttyUSB_LIDAR are fixed names for the Arduino Microcontroller and the Lidar Scanner respectively.

For more information you can take a look at this external tutorial: [Here](https://www.freva.com/assign-fixed-usb-port-names-to-your-raspberry-pi/)

Create robot workspace

Let’s create our workspace and build from source this repository.

cd ~
mkdir robot_ws/src -p

Clone this repository in the src folder

cd robot_ws/src
git clone <repository_address>

Install dependencies via rosdep:

cd ~/robot_ws

When it is the first time you run rosdep:

rosdep update

Make sure to export the ROS_DISTRO environment variable:

export ROS_DISTRO=humble

And then proceed to install the workspace dependencies:

rosdep install --from-paths src -i -y -r

Note that option -r has been added. For ARM based processors, there are missing packages, e.g. those related to simulation. We would not try to run the simulation in the compute platform of andino, however for convenience it is added here.

Let’s source the ROS Humble installation:

source /opt/ros/humble/setup.bash

Let’s build the packages (andino_gz_classic and andino_navigation work only in simulation):

colcon build --packages-skip andino_gz_classic andino_navigation

After building is completed:

source install/setup.bash

After this, you are good to go and use the robot! Refer to usage section.

Extra Recommendations & Tools

Network

Via terminal the wifi connection can be switched by doing:

List available wifi networks:

sudo nmcli dev wifi list

Connect to the desired one:

sudo nmcli --ask dev wifi connect <SSID>

Copy files remotely

Using scp is a useful tool when copying files remotely over ssh.

For copying a folder from host to remote unit:

scp -r <path/to/folder> <remote_user>@<remote_ip>:<remote_path_to_folder>

ROS Domain ID

The domain ID is used by DDS to compute the UDP ports that will be used for discovery and communication.

When using a “public” network using the domain id is a good technique to avoid extra noise with other ROS 2 system in the same network.

See ROS_DOMAIN_ID

TLDR? Export an environment variable with the same ID in all ROS 2 clients in the network for a correct discovery:

export ROS_DOMAIN_ID=<a_number_between_0_and_101>