Chapter 6: LED Control | EngineAI Open Platform

1 Interface Overview

The LED control interface is used to control the LED light effects on the robot, supporting various colors and LED effect modes (blinking, constant on, breathing, water flow, etc.). Developers switch LED modes by publishing the LedControl message, and the command takes effect immediately.

2 Message Fields and Mode Enum

Communication Interface:

Topic Name	Message Type	Direction	Description
`/hardware/led_control`	`LedControl.msg`	Client → Lighting Control Service	Send lighting control request

The complete message definition can be found in the GitHub Message Directory.

Supported LED Modes:

Mode Constant	Description	Effect
`0`	Restore	Restore built-in lighting
`BLINK_RED`	Red blinking	LED red fast blinking
`BLINK_GREEN`	Green blinking	LED green fast blinking
`BLINK_BLUE`	Blue blinking	LED blue fast blinking
`BLINK_WHITE`	White blinking	LED white fast blinking
`CONSTANT_ON_WHITE`	White constant on	LED white continuously lit
`CONSTANT_ON_GREEN`	Green constant on	LED green continuously lit
`BREATHE_WHITE`	White breathing	LED white breathing effect
`WATER_WHITE`	White water flow	LED white water flow effect
`BREATHE_RED`	Red breathing	LED red breathing effect
`BLINK_ORANGE`	Orange blinking	LED orange fast blinking
`CONSTANT_ON_ORANGE`	Orange constant on	LED orange continuously lit

3 Example: LED Mode Cycling

File Name: led_control_example.py

This example automatically switches the LED mode every 1 second, cycling through all available lighting effects.

Run Command:

Bash

python3 src/interface_example/scripts/led_control_example.py

Custom LED Control:

Python

import rclpy
from rclpy.node import Node
from interface_protocol.msg import LedControl

class LedControlExample(Node):
    def __init__(self):
        super().__init__("led_control_example")
        self.pub = self.create_publisher(LedControl, "/hardware/led_control", 10)
        # Switch LED mode every 1 second
        self.modes = [LedControl.BLINK_RED, LedControl.BREATHE_WHITE,
                      LedControl.CONSTANT_ON_GREEN, LedControl.WATER_WHITE]
        self.idx = 0
        self.create_timer(1.0, self._tick)

    def _tick(self):
        msg = LedControl()
        msg.color = self.modes[self.idx]
        self.pub.publish(msg)
        self.get_logger().info(f"LED mode: {self.modes[self.idx]}")
        self.idx = (self.idx + 1) % len(self.modes)

rclpy.init()
rclpy.spin(LedControlExample())

4 Notes

LED control commands take effect immediately
It is recommended to control the publishing frequency to avoid overly frequent switching
Some mode combinations may not be supported by the hardware
If a built-in system error or warning occurs, the ROS2 lighting design interface will become invalid

📎 Source files in the open-source repository for this chapter (click file name to jump to GitHub): LedControl.msg · led_control_example.py