LED Control on RPi4B using ROS2 Topic by C++

CMakeLists.txt

cmake_minimum_required(VERSION 3.5) project(my_pkg_cpp) # Default to C99 if(NOT CMAKE_C_STANDARD)   set(CMAKE_C_STANDARD 99) endif() # Default to C++14 if(NOT CMAKE_CXX_STANDARD)   set(CMAKE_CXX_STANDARD 14) endif() 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) # uncomment the following section in order to fill in # further dependencies manually. # find_package(<dependency> REQUIRED) find_package(rclcpp REQUIRED) find_package(std_msgs REQUIRED) add_executable(pub_node_led src/my_pub_led.cpp) ament_target_dependencies(pub_node_led rclcpp std_msgs) add_executable(sub_node_led src/my_sub_led.cpp) ament_target_dependencies(sub_node_led rclcpp std_msgs) target_link_libraries(sub_node_led wiringPi) install(TARGETS   pub_node_led   sub_node_led   DESTINATION lib/${PROJECT_NAME}) if(BUILD_TESTING)   find_package(ament_lint_auto REQUIRED)   # the following line skips the linter which checks for copyrights   # uncomment the line when a copyright and license is not present in all source files   #set(ament_cmake_copyright_FOUND TRUE)   # the following line skips cpplint (only works in a git repo)   # uncomment the line when this package is not in a git repo   #set(ament_cmake_cpplint_FOUND TRUE)   ament_lint_auto_find_test_dependencies() endif() ament_package()

package.xml

<?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>my_pkg_cpp</name>   <version>0.0.0</version>   <description>TODO: Package description</description>   <maintainer email="ubuntu@todo.todo">ubuntu</maintainer>   <license>TODO: License declaration</license>   <buildtool_depend>ament_cmake</buildtool_depend>   <depend>rclcpp</depend>   <depend>std_msgs</depend>   <test_depend>ament_lint_auto</test_depend>   <test_depend>ament_lint_common</test_depend>   <export>     <build_type>ament_cmake</build_type>   </export> </package>

my_pub_led.cpp 

#include <chrono> #include <functional> #include <memory> #include <string> #include "rclcpp/rclcpp.hpp" #include "std_msgs/msg/string.hpp" using namespace std::chrono_literals; /* This example creates a subclass of Node and uses std::bind() to register a * member function as a callback from the timer. */ class PublisherLed : public rclcpp::Node {   public:     PublisherLed()     : Node("publisher_led"), count_(0)     {       publisher_ = this->create_publisher<std_msgs::msg::String>("topic_led", 10);       timer_ = this->create_wall_timer(       3000ms, std::bind(&PublisherLed::timer_callback, this));     }   private:     void timer_callback()     {       auto message = std_msgs::msg::String();       message.data = "LED ON " + std::to_string(count_++);       RCLCPP_INFO(this->get_logger(), "Published: '%s'", message.data.c_str());       publisher_->publish(message);     }     rclcpp::TimerBase::SharedPtr timer_;     rclcpp::Publisher<std_msgs::msg::String>::SharedPtr publisher_;     size_t count_; }; int main(int argc, char * argv[]) {   rclcpp::init(argc, argv);   rclcpp::spin(std::make_shared<PublisherLed>());   rclcpp::shutdown();   return 0; }

my_sub_led.cpp

#include <iostream> #include <memory> #include "rclcpp/rclcpp.hpp" #include "std_msgs/msg/string.hpp" using std::placeholders::_1; #include <wiringPi.h> class SubscriberLed : public rclcpp::Node {   public:     SubscriberLed()     : Node("subscriber_led")     {       subscription_ = this->create_subscription<std_msgs::msg::String>(       "topic_led", 10, std::bind(&SubscriberLed::topic_callback, this, _1));     }   private:     void topic_callback(const std_msgs::msg::String::SharedPtr msg) const     {       // Setup for RPi4B       auto LED26 = 26;              wiringPiSetupGpio();       pinMode(LED26, OUTPUT);       digitalWrite(LED26, HIGH);       delay(1000);       digitalWrite(LED26, LOW);              RCLCPP_INFO(this->get_logger(), "Subscribed: '%s'", msg->data.c_str());     }     rclcpp::Subscription<std_msgs::msg::String>::SharedPtr subscription_; }; int main(int argc, char * argv[]) {        rclcpp::init(argc, argv);   rclcpp::spin(std::make_shared<SubscriberLed>());   rclcpp::shutdown();   return 0; }

ros2 run my_pkg_cpp pub_node_led

ros2 run my_pkg_cpp sub_node_led