Magnetometer ROS Node

This package provides a ROS1 node for reading raw magnetometer data from a Yahboom IMU via serial interface, performing a simple calibration, and publishing the data as a sensor_msgs/MagneticField topic.

Requirements

Install dependencies:

sudo apt install python3-serial

Installation

1. Clone this package:

cd ~/catkin_ws/src
git clone git@github.com:CJT-Robotics/magnetometer.git
sudo chmod +x ~/catkin_ws/src/magnetometer/src/mag_pub.py

2. Build the workspace:

cd ~/catkin_ws
catkin build
source devel/setup.bash

udev Rule

To ensure the magnetometer is always accessible under a fixed device name, create a udev rule.

1. Find your USB device

lsusb

Example output:

Bus 001 Device 014: ID 1a86:7523 QinHeng Electronics HL-340 USB-Serial adapter

• 1a86 = idVendor
• 7523 = idProduct

---

2. Create udev rule

sudo nano /etc/udev/rules.d/99-magnetometer.rules

Add:

SUBSYSTEM=="tty", ATTRS{idVendor}=="1a86", ATTRS{idProduct}=="7523", SYMLINK+="mag_yahboom", MODE="0666"

3. Reload rules

sudo udevadm control --reload-rules
sudo udevadm trigger

Reconnect the device. Check:

ls -l /dev/mag_yahboom

Usage

Run the node:

rosrun magnetometer mag_pub.py

Published topic:

{namesapce}/imu/mag (sensor_msgs/MagneticField)

Calibration

On startup, the node performs a calibration for a few seconds.

Data Processing

• Raw values are read from serial
• Packet structure is validated via checksum
• Magnetometer values are extracted
• Offset is subtracted
• Values are scaled

Notes

• Ensure correct permissions (MODE="0666") or add your user to dialout
• If no data appears, verify:
  • correct baud rate (115200)
  • correct device path
  • serial cable / adapter