TopicFS — How It Works

TopicFS approach bash — 12 lines

# 1. Read live arm position
cat /mnt/topicfs/swiftpro/position/latest
{"x":226.6,"y":-2.8,"z":19.9}

# 2. Send a move command
echo '{"j1":90,"j2":45,"j3":45,"speed":5000,"wait":false}' \
  > /mnt/topicfs/swiftpro/set_servo_angles/command

# 3. Read the response
cat /mnt/topicfs/swiftpro/set_servo_angles/response
{"success":true}

# 4. Reset the arm
echo '{}' > /mnt/topicfs/swiftpro/reset/command
cat /mnt/topicfs/swiftpro/reset/response
{"success":true}

what you need on the host

any language that can open a file
zero ROS2 packages installed
zero compiled message libraries
zero knowledge of DDS or topic types
one running container (TopicFS)

Traditional ROS2 approach Python — ~60 lines

# Requires: ROS2 installed, sourced,
# swiftpro_resources pkg built + installed

import rclpy
from rclpy.node import Node
from geometry_msgs.msg import Point
from std_msgs.msg import Bool
from swiftpro_resources.srv import SetServoAngles, Reset

class ArmController(Node):
  def __init__(self):
    super().__init__('arm_controller')
    # 1. Subscribe to position topic
    self.position = None
    self.create_subscription(
      Point, '/swiftpro/position',
      lambda msg: setattr(self, 'position', msg),
      10
    )
    # 2+3. Create service client for move
    self.move_cli = self.create_client(
      SetServoAngles, '/swiftpro/set_servo_angles'
    )
    while not self.move_cli.wait_for_service(
      timeout_sec=1.0):
      self.get_logger().info('waiting for move...')
    # 4. Create service client for reset
    self.reset_cli = self.create_client(
      Reset, '/swiftpro/reset'
    )
    while not self.reset_cli.wait_for_service(
      timeout_sec=1.0):
      self.get_logger().info('waiting for reset...')

  def get_position(self):
    # spin until first message received
    while self.position is None:
      rclpy.spin_once(self, timeout_sec=0.1)
    return self.position  # Point(x,y,z)

  def move(self, j1, j2, j3):
    req = SetServoAngles.Request()
    req.j1, req.j2, req.j3 = j1, j2, j3
    req.speed = 5000; req.wait = False
    future = self.move_cli.call_async(req)
    rclpy.spin_until_future_complete(self, future)
    return future.result().success  # bool

  def reset(self):
    req = Reset.Request()
    future = self.reset_cli.call_async(req)
    rclpy.spin_until_future_complete(self, future)
    return future.result().success  # bool

rclpy.init()
node = ArmController()
pos = node.get_position()   # 1. position
ok  = node.move(90,45,45)    # 2. move
print(ok)                     # 3. response
ok  = node.reset()           # 4. reset
print(ok)

what you need on the host

ROS2 Jazzy fully installed + sourced
swiftpro_resources package built
compiled message typesupport .so files
colcon build system
understanding of DDS, QoS, spin loops
Python rclpy bindings
service client lifecycle management