Day 3: ROS Motor Driver Node

This is where ROS takes control of the robot.

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1. ROS Concept

• /cmd_vel topic
• geometry_msgs/Twist

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2. Motor Driver ROS Node

#!/usr/bin/env python3
import rospy
from geometry_msgs.msg import Twist
import RPi.GPIO as GPIO

def callback(msg):
    linear = msg.linear.x
    angular = msg.angular.z
    # logic here

rospy.init_node("motor_driver")
rospy.Subscriber("/cmd_vel", Twist, callback)
rospy.spin()

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3. Test Using rostopic

rostopic pub /cmd_vel geometry_msgs/Twist "linear:
  x: 0.3
angular:
  z: 0.0"

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Next → Day 4: Keyboard control