Feature: LED Colour Controller Package

src/led_controller/CMakeLists.txt

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+cmake_minimum_required(VERSION 3.8)
+project(led_controller)
+
+if(CMAKE_COMPILER_IS_GNUCXX OR CMAKE_CXX_COMPILER_ID MATCHES "Clang")
+  add_compile_options(-Wall -Wextra -Wpedantic)
+endif()
+
+# find dependencies
+find_package(ament_cmake REQUIRED)
+find_package(rosidl_default_generators REQUIRED)
+find_package(rclcpp REQUIRED)
+find_package(rclcpp_lifecycle REQUIRED)
+# uncomment the following section in order to fill in
+# further dependencies manually.
+# find_package(<dependency> REQUIRED)
+
+set(msg_files
+  "msg/RGB.msg"
+)
+
+rosidl_generate_interfaces(${PROJECT_NAME}
+  ${msg_files}
+)
+
+ament_export_dependencies(rosidl_default_runtime)
+
+add_executable(led_colour_controller src/led_colour_controller.cpp)
+ament_target_dependencies(led_colour_controller
+  rclcpp
+  rclcpp_lifecycle
+)
+
+rosidl_get_typesupport_target(cpp_typesupport_target
+  ${PROJECT_NAME} rosidl_typesupport_cpp)
+
+target_link_libraries(led_colour_controller "${cpp_typesupport_target}")
+
+# Replacing the rosidl_get_typesupport_target and target_link_libraries lines above with the one below also works
+# target_link_libraries(led_colour_controller ${PROJECT_NAME}__rosidl_typesupport_cpp)
+
+install(TARGETS led_colour_controller
+  DESTINATION lib/${PROJECT_NAME})
+
+if(BUILD_TESTING)
+  find_package(ament_lint_auto REQUIRED)
+  # the following line skips the linter which checks for copyrights
+  # comment the line when a copyright and license is added to all source files
+  set(ament_cmake_copyright_FOUND TRUE)
+  # the following line skips cpplint (only works in a git repo)
+  # comment the line when this package is in a git repo and when
+  # a copyright and license is added to all source files
+  set(ament_cmake_cpplint_FOUND TRUE)
+  ament_lint_auto_find_test_dependencies()
+endif()
+
+ament_package()

src/led_controller/LICENSE

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+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.

src/led_controller/msg/RGB.msg

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+uint8 red_val
+uint8 green_val
+uint8 blue_val

src/led_controller/package.xml

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+<?xml version="1.0"?>
+<?xml-model href="http://download.ros.org/schema/package_format3.xsd" schematypens="http://www.w3.org/2001/XMLSchema"?>
+<package format="3">
+  <name>led_controller</name>
+  <version>0.0.0</version>
+  <description>TODO: Package description</description>
+  <maintainer email="dev3@todo.todo">dev3</maintainer>
+  <license>MIT</license>
+
+  <depend>rclcpp</depend>
+  <depend>rclcpp_lifecycle</depend>
+
+  <buildtool_depend>ament_cmake</buildtool_depend>
+  <buildtool_depend>rosidl_default_generators</buildtool_depend>
+
+  <exec_depend>rosidl_default_runtime</exec_depend>
+
+  <member_of_group>rosidl_interface_packages</member_of_group>
+
+  <test_depend>ament_lint_auto</test_depend>
+  <test_depend>ament_lint_common</test_depend>
+
+  <export>
+    <build_type>ament_cmake</build_type>
+  </export>
+</package>

src/led_controller/src/led_colour_controller.cpp

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+#include <chrono>
+#include <cstdlib>
+
+#include "rclcpp/rclcpp.hpp"
+#include "rclcpp_lifecycle/lifecycle_node.hpp"
+#include "led_controller/msg/rgb.hpp"
+
+using namespace std::chrono_literals;
+
+using LifecycleCallback = rclcpp_lifecycle::node_interfaces::LifecycleNodeInterface::CallbackReturn;
+
+class LedColourControllerNode : public rclcpp_lifecycle::LifecycleNode {
+    public:
+        explicit LedColourControllerNode(const std::string &name) : rclcpp_lifecycle::LifecycleNode(name) {}
+
+        LifecycleCallback on_configure(const rclcpp_lifecycle::State &) {
+            RCLCPP_INFO(this->get_logger(), "Configuring LED Colour Controller");
+
+            pub_ = this->create_publisher<led_controller::msg::RGB>("led_colour", 10);
+
+            timer_ = this->create_wall_timer(1s, std::bind(&LedColourControllerNode::publish_random_colour, this));
+            timer_->cancel(); // Start with the timer stopped
+
+            publish_colour(255, 255, 0); // Turn to yellow after configuring
+
+            return LifecycleCallback::SUCCESS;
+        }
+
+        LifecycleCallback on_activate(const rclcpp_lifecycle::State &state) {
+            RCLCPP_INFO(this->get_logger(), "Activating LED Colour Controller");
+
+            LifecycleNode::on_activate(state);
+
+            timer_->reset(); // Resume timer on activate
+
+            return LifecycleCallback::SUCCESS;
+        }
+
+        LifecycleCallback on_deactivate(const rclcpp_lifecycle::State &state) {
+            RCLCPP_INFO(this->get_logger(), "Deactivating LED Colour Controller");
+
+            LifecycleNode::on_deactivate(state);
+
+            timer_->cancel();
+
+            publish_colour(255, 0, 0); // Turn to red on deactivate
+
+            return LifecycleCallback::SUCCESS;
+        }
+
+        LifecycleCallback on_cleanup(const rclcpp_lifecycle::State &state) {
+            RCLCPP_INFO(this->get_logger(), "Cleaning up LED Colour Controller");
+
+            timer_.reset();
+            pub_.reset();
+
+            return LifecycleCallback::SUCCESS;
+        }
+
+        LifecycleCallback on_shutdown(const rclcpp_lifecycle::State &state) {
+            RCLCPP_INFO(this->get_logger(), "Shuting down LED Colour Controller");
+
+            timer_.reset();
+            pub_.reset();
+
+            return LifecycleCallback::SUCCESS;
+        }
+
+    private:
+        void publish_colour(std::uint8_t r, std::uint8_t g, std::uint8_t b) {
+            auto colour = std::make_unique<led_controller::msg::RGB>();
+            colour->red_val = r;
+            colour->green_val = g;
+            colour->blue_val = b;
+
+            RCLCPP_INFO(this->get_logger(), "Publishing colour: R(%d), G(%d), B(%d)", colour->red_val, colour->green_val, colour->blue_val);
+            pub_->publish(std::move(colour));
+        };
+        void publish_random_colour() {
+            publish_colour(rand() % 256, rand() % 256, rand() % 256);
+        };
+
+        // Using regular publisher to allow colour changing in inactive state
+        std::shared_ptr<rclcpp::Publisher<led_controller::msg::RGB>> pub_;
+        std::shared_ptr<rclcpp::TimerBase> timer_;
+};
+
+int main(int argc, char * argv[]) {
+    rclcpp::init(argc, argv);
+
+    rclcpp::executors::SingleThreadedExecutor executor;
+    auto node = std::make_shared<LedColourControllerNode>("led_colour_controller_node");
+
+    executor.add_node(node->get_node_base_interface());
+    executor.spin();
+
+    rclcpp::shutdown();
+    return 0;
+}