ROS2 Bridge Overview

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Channel Compatibility (PCAN + slcan + Damiao Serial Bridge)

• Linux SocketCAN uses interface names directly: can0, can1, slcan0.
• For USB-serial CAN adapters, bring up slcan0 first: sudo slcand -o -c -s8 /dev/ttyUSB0 slcan0 && sudo ip link set slcan0 up.
• Damiao-only serial bridge transport is also available in CLI (--transport dm-serial --serial-port /dev/ttyACM0 --serial-baud 921600).
• Full Damiao serial-bridge interface list and command patterns are documented in motor_cli/README.md (section 3.6 in motor_cli/README.zh-CN.md).
• On Linux SocketCAN, do not append bitrate in --channel (for example can0@1000000 is invalid).
• On Windows (PCAN backend), can0/can1 map to PCAN_USBBUS1/2; optional @bitrate suffix is supported.

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Features

• Subscribe command topic and execute motor commands
• Publish motor state periodically
• Expose operational commands via same command topic:
  • scan
  • set_id
  • verify

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Topics

• Subscribed: /motorbridge/cmd (std_msgs/String, JSON payload)
• Published:
  • /motorbridge/state (std_msgs/String, JSON payload)
  • /motorbridge/event (std_msgs/String, JSON payload)

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Command JSON

{"op":"enable"}
{"op":"disable"}
{"op":"mit","pos":0.0,"vel":0.0,"kp":20.0,"kd":1.0,"tau":0.0,"continuous":true}
{"op":"pos_vel","pos":3.10,"vlim":1.50,"continuous":true}
{"op":"vel","vel":0.5,"continuous":true}
{"op":"force_pos","pos":0.8,"vlim":2.0,"ratio":0.3,"continuous":true}

{"op":"scan","start_id":1,"end_id":16,"feedback_base":16,"timeout_ms":100}
{"op":"set_id","old_motor_id":2,"old_feedback_id":18,"new_motor_id":5,"new_feedback_id":21,"store":true,"verify":true}
{"op":"verify","motor_id":5,"feedback_id":21,"timeout_ms":1000}

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Run

• ROS2 installed (rclpy, std_msgs)
• motorbridge Python package importable

PYTHONPATH=bindings/python/src:$PYTHONPATH \
python3 integrations/ros2_bridge/python/motorbridge_ros2_bridge.py \
  --channel can0 --model 4340P --motor-id 0x01 --feedback-id 0x11 --dt-ms 20

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Publish command examples

ros2 topic pub --once /motorbridge/cmd std_msgs/msg/String '{data: "{\"op\":\"enable\"}"}'
ros2 topic pub --once /motorbridge/cmd std_msgs/msg/String '{data: "{\"op\":\"vel\",\"vel\":0.5,\"continuous\":true}"}'
ros2 topic pub --once /motorbridge/cmd std_msgs/msg/String '{data: "{\"op\":\"scan\",\"start_id\":1,\"end_id\":16}"}'

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Notes

• continuous=true means command is resent at each timer tick (--dt-ms).
• enable/disable/scan/set_id/verify are one-shot operations.