ROS2 CAN interface

ros2_can_interface is a ROS 2 package designed to facilitate seamless communication between ROS 2 topics and Controller Area Network (CAN) messages. It provides two primary nodes:

1. ROS2 to CAN Publisher (ros2can): Subscribes to specified ROS 2 topics, serializes the messages, segments them if necessary, and transmits them over the CAN bus.

2. CAN to ROS2 Subscriber (can2ros): Listens for CAN messages, reassembles segmented messages, deserializes them, and publishes the data to corresponding ROS 2 topics.

This package is particularly useful in robotics and automotive applications where integrating ROS 2 systems with CAN-based hardware is required.

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Table of Contents

• Features
• Prerequisites
• Installation
• Configuration
• Usage
  • Building the Package
  • Running the Nodes
• Testing
• Troubleshooting
• Package Structure
• Dependencies
• Contributing
• License
• Acknowledgments

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Features

• Bidirectional Communication: Convert ROS 2 messages to CAN frames and vice versa.
• Custom Segmentation: Automatically segment large messages into multiple CAN frames based on configuration.
• Flexible Configuration: Define mappings between ROS 2 topics and CAN messages using a YAML configuration file.
• Threaded CAN Listener: Efficiently listen to CAN bus messages without blocking ROS 2 operations.
• Logging: Comprehensive logging for monitoring and debugging.

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Prerequisites

• Operating System: Ubuntu 20.04 or later (compatible with ROS 2 distributions like Foxy, Galactic, etc.)
• ROS 2: Installed and properly sourced.
• Python 3: Version 3.8 or later.
• CAN Interface Hardware: Such as USB-CAN adapters. Alternatively, use a virtual CAN interface (vcan) for testing.

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Installation

1. Set Up Your ROS 2 Workspace:

   cd ~/psd_ws/src

2. Clone the Package:

   git clone https://github.com/rimaturus/ros2_can_interface.git

3. Install Python Dependencies:

   pip install python-can pyyaml ament_index_python --break-system-packages 

   Achtung! [WIP cleaner fix]

4. Build the Package:

   cd ~/psd_ws/
   colcon build --packages-select ros2_can_interface

5. Source the Workspace:

   source install/setup.bash

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Configuration

mapping.yaml

The mapping.yaml file defines how ROS 2 topics map to CAN messages and vice versa. It specifies CAN IDs, message fields, data types, and segmentation parameters.

Location: ros2_can_interface/config/mapping.yaml

Sample mapping.yaml:

ros_to_can:
  /psd_vehicle/pose:
    can_id_base: 0x200
    fields:
      car_x: 
        start_bit: 0
        length: 32
        type: float
      car_y:
        start_bit: 32
        length: 32
        type: float
      car_yaw:
        start_bit: 64
        length: 32
        type: float
    segmentation:
      max_payload: 8  # bytes per CAN frame
      segments:
        - offset: 0  # bytes
        - offset: 4
        - offset: 8

can_to_ros:
  /actuator/command:
    can_id_base: 0x200
    fields:
      command:
        start_bit: 0
        length: 16
        type: int
      value:
        start_bit: 16
        length: 32
        type: float
    segmentation:
      max_payload: 8  # bytes per CAN frame
      segments:
        - offset: 0
        - offset: 4

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Usage

Building the Package

If you've made changes to the package or added new dependencies, rebuild the workspace:

cd ~/psd_ws/
colcon build --packages-select ros2_can_interface
source install/setup.bash

Running the Nodes

1. Run the ROS2 to CAN Publisher Node (ros2can)

This node subscribes to ROS 2 topics and publishes corresponding CAN messages.

ros2 run ros2_can_interface ros2can

2. Run the CAN to ROS2 Subscriber Node (can2ros)

This node listens to CAN messages and publishes corresponding ROS 2 topics.

ros2 run ros2_can_interface can2ros

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Testing

Using Virtual CAN (vcan) for Testing

1. Set Up Virtual CAN Interface:

   sudo modprobe vcan
   sudo ip link add dev vcan0 type vcan
   sudo ip link set up vcan0

2. Monitor CAN Traffic:

   Use candump to monitor CAN messages:

   candump vcan0

3. Send Test CAN Messages:

   Use cansend to send test messages:

   cansend vcan0 100#1122334455667788

4. Publish Test ROS 2 Messages:

   In a new terminal, publish a test message:

   ros2 topic pub /psd_vehicle/pose std_msgs/msg/Float32MultiArray "data: [25.5, 3.2, -1.1]"

5. Verify Reception:

   Echo the ROS 2 subscriber topic:

   ros2 topic echo /actuator/command

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Troubleshooting

Common Issues and Solutions

• ModuleNotFoundError: No module named 'ros2_can_interface.ros2can':

  Ensure that ros2can.py is correctly placed inside the ros2_can_interface package and setup.py is correctly configured.

• AttributeError: property 'subscriptions' of 'ROS2ToCANPublisher' object has no setter:

  Rename self.subscriptions to self.subscription_list or another non-conflicting name in your scripts.

• CAN Bus Not Initializing:

  Verify the CAN interface name and permissions. Add your user to the can group:

  sudo usermod -aG can $USER

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Package Structure

ros2_can_interface/
├── config
│   └── mapping.yaml
├── package.xml
├── README.md
├── resource
│   └── ros2_can_converter
├── ros2_can_converter
│   ├── can2ros.py
│   ├── __init__.py
│   └── ros2can.py
├── setup.cfg
├── setup.py
└── test
    ├── test_copyright.py
    ├── test_flake8.py
    └── test_pep257.py

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Dependencies

• ROS 2 Packages: rclpy, std_msgs
• Python Packages: python-can, pyyaml, ament_index_python
• System Packages: can-utils

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Contributing

Contributions are welcome! Please follow these steps:

1. Fork the Repository.
2. Create a Branch.
3. Commit Changes.
4. Open a Pull Request.

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License

This project is licensed under the Apache License 2.0. See the LICENSE file for details.

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Acknowledgments

• ROS 2 Community
• Python CAN Library Authors
• Open-Source Contributors

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Happy Coding! 🚀