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RoboCrew

May your ports be ever named the same

To ensure that your robot arms and cameras are consistently recognized on your Raspberry Pi, you need to set up udev rules. This will allow you to have fixed device names (e.g., /dev/robot_arm and /dev/robot_camera) regardless of the order in which they are connected.

Section titled “1. Automatic Setup (Recommended)”

The easiest way to configure your robot is to use the built-in interactive script. This script guides you through connecting each component one by one to identify them.

How to run:

Section titled “How to run:”
  1. Open a terminal and run the setup command:
Terminal window
robocrew-setup-usb-modules

  1. Follow the prompts:

    • Disconnect all RoboCrew USB devices when asked.
    • Connect the USB for each specific alias (e.g., camera_center, arm_right) one at a time and press Enter.
    • The script will detect the new device, capture its unique ID and serial number, and map it to the correct name.

  2. Apply Rules: The script automatically saves the rules to /etc/udev/rules.d/99-robocrew.rules and reloads the system configuration.

2. Manual Identification

Section titled “2. Manual Identification”

If you need to check how your devices are currently mapped, you can use standard Linux commands:

  • Check Arm/Serial Symlinks:
Terminal window
ls -l /dev/arm*

Example output: lrwxrwxrwx 1 root root 7 Dec 2 11:40 /dev/arm_right -> ttyACM2.

  • Check Camera Symlinks:
Terminal window
ls -l /dev/cam*

Example output: lrwxrwxrwx 1 root root 6 Dec 2 11:40 /dev/camera_center -> video0.

3. How the Rules Work

Section titled “3. How the Rules Work”

The system generates rules based on the device’s Vendor ID, Product ID, and Serial Number.

  • Standard Mapping: If a device has a unique serial number, it is used for identification.
  • Physical Path Mapping: If multiple identical devices (same Vendor/Product ID) lack unique serial numbers, the script uses their physical USB port path to distinguish between them.
  • Camera Indexing: For video devices, the rules specifically target index 0 to ensure they capture the primary video stream rather than metadata streams.

4. Default Assignments

Section titled “4. Default Assignments”

The project typically looks for the following default symlinks during setup:

  • camera_center, camera_right, camera_left
  • arm_right, arm_left

By using these persistent names in your Python scripts (e.g., RobotCamera("/dev/camera_center")), your robot becomes hardware-agnostic regarding which physical USB port is used.