CLEARPATH TurtleBot 4 Lite, User Manual

Page: 118 / 153

Create a lightring publisher
Now that we can receive a button press, lets create a lightring publisher.
class TurtleBot4FirstNode (Node):
def __init__ (self):
super ().__init__( 'turtlebot4_first_python_node' )
# Subscribe to the /interface_buttons topic
self
.interface_buttons_subscriber = self.create_subscription(
InterfaceButtons,
'/interface_buttons' ,
self .interface_buttons_callback,
qos_profile_sensor_data)
# Create a publisher for the /cmd_lightring topic
self
.lightring_publisher = self.create_publisher(
LightringLeds,
'/cmd_lightring' ,
qos_profile_sensor_data)
Note
The Lightring publisher uses the LightringLeds message type.
Next, lets create a function that will populate a LightringLeds message, and publish it.
Add this code below your interface_buttons_callback function:
def button_1_function (self):
# Create a ROS2 message
lightring_msg = LightringLeds()
# Stamp the message with the current time
lightring_msg.header.stamp = self .get_clock().now().to_msg()
# Override system lights
lightring_msg.override_system = True
# LED 0
lightring_msg.leds[ 0 ].red = 255
lightring_msg.leds[ 0 ].blue = 0
lightring_msg.leds[ 0 ].green = 0