ROS2 node for controlling PWM boards based on the PCA9685 chip with an I²C interface. Primary use is for controlling RC Servos and DC motors via PWM. This is based on ros-i2cpwmboard (OUTDATED) with updates to make it work on ROS2.
To see a practical use of this project, see the SMOV project.
At present, there is no complete new documentation for the project. However, you can access the documentation for the old version of the project (the changes to be made to the terminal are minimal, as it uses ROS1, and the core functionality remains the same). You can access it by clicking here or here.
The calibration package will help you find the center and critical values of your servos. Click here to take a look.
When you launch the program, you can now choose your I²C bus. Here's an example:
ros2 run i2c_pwm_board node 1 # The "1" tells the program to open the i2c-1/ bus, but you can change it to your desired bus.This will be particularly useful for opening several buses between programs, and for easily adapting to the RPi Zero, which has an i2c-0/ bus by default.
When you run the node, the topics & services will end with the bus number as a suffix (in example, [service_name]_1 for the i2c-1/ bus).
# Setting PWM frequency to 50Hz.
ros2 service call /set_pwm_frequency_1 i2c_pwm_board_msgs/srv/IntValue "{value: 50}"
# Configuring two servos.
ros2 service call /config_servos_1 i2c_pwm_board_msgs/srv/ServosConfig "servos: [{servo: 1, center: 333, range: 100, direction: -1},{servo: 2, center: 336, range: 108, direction: 1}]"
# Configuring those two servos on differential mode.
ros2 service call /config_drive_mode_1 i2c_pwm_board_msgs/srv/DriveMode "{mode: differential, rpm: 56.0, radius: 0.0055, track: 0.015, scale: 1.0,servos: [{servo: 1, position: 1}, {servo: 2, position: 2}]}"
# Drive both servos forward using proportional value between [-1; 1].
ros2 topic pub -1 /servos_proportional_1 i2c_pwm_board_msgs/msg/ServoArray "{servos:[{servo: 1, value: 0.40}, {servo: 2, value: 0.40}]}"You need to have ROS2 installed (of course) and these packages provided by the default desktop installation below :
- rclcpp, std_msgs, std_srvs, geometry_msgs
- rosidl_default_generators, rosidl_default_runtime
- Have
python3-colcon-common-extensionsinstalled - Have
libi2c-devandi2c-toolsinstalled - Have the xmlrpcpp package
You can clone and run this package by copying the command below :
- Note that if you want to run this project, you have to clone the xmlrpcpp packages :
git clone --recursive https://github.com/vertueux/i2c_pwm_board.gitYou can install the i2c library and colcon by running the install scripts located at scripts/install_dependencies.sh.
Simply just copy & paste this code :
cd scripts/
chmod +x install_dependencies.sh
./install_dependenciesMake sure that I²C is enabled by default. Check the file /boot/firmware/syscfg.txt and see if you have the following line:
dtparam=i2c_arm=onIf not, maybe you can append them on /boot/firmware/usercfg.txt and reboot, and hopefully, that works. If that doesn't work, maybe do sudo apt update && sudo full-upgrade -y and see if there are any distro updates needed.
- Refer to this post.
You can also add the following line to /etc/modules:
i2c-dev- Refer to this post.
On a RPi, with raspi-config, you can enable I²C by navigating to Interface Options->Advanced->I²C and then enable it.
If you're not using a second microcontroller and you don't have an LCD panel, you can go straight to the next step.
Now when you log in you can type the following command to see all the connected devices:
sudo i2cdetect -y 1 # Or 0, depends on the device you use.source /opt/ros/humble/setup.bash # With Debian binaries.
cd /i2c_pwm_board/
colcon build
source install/setup.bash # Do not change directory.In order to run the project, you just have to perform this command :
ros2 run i2c_pwm_board node # You can add your I²C bus address as a digit (like 1 to open i2c-1/).