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micro-ROS + PlatformIO: Custom Message Integration
Build a micro-ROS system on your microcontroller using PlatformIO.
Define and publish custom ROS 2 messages like IMU orientation data (roll, pitch, yaw).
Reliable. Modular. Real-time ready.

Requirements

Ubuntu (20.04 or later)

ROS 2 (Humble)

PlatformIO Core

micro-ROS

MCU board (e.g., STM32 + WIZnet W5500 for Ethernet)

1. PlatformIO Setup

Install PlatformIO:
pip install platformio

Clone your micro-ROS project and build:

git clone <your-micro-ros-repo>
cd <your-micro-ros-repo>
pio lib install
pio run
pio run --target upload

Select the correct environment in platformio.ini.

2. Setup micro-ROS Agent

Install ROS 2 and source environment:

sudo apt install ros-humble-desktop
source /opt/ros/humble/setup.bash

Clone and build the agent workspace:

mkdir -p ~/uros_ws/src
cd ~/uros_ws/src
git clone -b humble https://github.com/micro-ROS/micro_ros_setup.git
cd ~/uros_ws
rosdep update
rosdep install --from-paths src --ignore-src -y
colcon build
source install/local_setup.bash

Create and run the agent:

ros2 run micro_ros_setup create_agent_ws.sh
ros2 run micro_ros_setup build_agent.sh
source install/local_setup.sh
ros2 run micro_ros_agent micro_ros_agent udp4 --port 8888 --agent-ip 192.168.x.x

3. Create a Custom Message (ROS 2)

Create a new package:

cd ~/your_ros2_ws/src
ros2 pkg create custom_msgs --build-type ament_cmake --dependencies rosidl_default_generators std_msgs

Define your message:
custom_msgs/msg/ImuInfo.msg

std_msgs/Header header
float64 roll
float64 pitch
float64 yaw

Edit CMakeLists.txt:

find_package(rosidl_default_generators REQUIRED)
rosidl_generate_interfaces(${PROJECT_NAME}
  "msg/ImuInfo.msg"
  DEPENDENCIES std_msgs
)

Edit package.xml:

<build_depend>rosidl_default_generators</build_depend>
<exec_depend>rosidl_default_runtime</exec_depend>

Build it:
colcon build --packages-select custom_msgs

4. Import Custom Message into PlatformIO

Copy the built custom_msgs folder into:
.pio/libdeps/<env>/micro_ros_platformio/extra_packages/

Update extra_packages.repos:

custom_msgs:
  type: local
  path: custom_msgs
  version: humble

Then copy the entire extra_packages/ folder into your PlatformIO project root.
Rebuild:
pio run

5. Use Your Message in Code

#include <custom_msgs/msg/imu_info.h>

rcl_publisher_t euler_pub;
custom_msgs__msg__ImuInfo euler_msg;

euler_msg.roll  = roll_value;
euler_msg.pitch = pitch_value;
euler_msg.yaw   = yaw_value;

RCLC_PUBLISH(&euler_pub, &euler_msg);

Find the struct definition at:
.pio/libdeps/<env>/.../imu_info__struct.h

6. Test & Visualize

In your ROS 2 terminal:

ros2 topic list
ros2 topic echo /imu/data
rqt_plot /imu/data/orientation/x:y:z
rviz2

Key Points

PlatformIO + micro-ROS integration

Custom message publishing over UDP

Real-time ROS 2 communication

Visualize with RViz or rqt_plot

Leverages WIZnet's reliable Ethernet stack

Simple. Modular. Real-time.
Perfect for robotics, drones, and smart sensors.