CreOS SDK
The CreOS SDK allows you to interact with Avular robots
 
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Hello World (ROS2 C++)

Hello World example using ROS2 in C++ to communicate with the CreOS SDK ROS2 node.

This example demonstrates how to use ROS2 in C++ to communicate with the CreOS SDK ROS2 node. Below you can find the full source code, including a CMakeLists.txt file that links the necessary libraries. You can also find a more detailed explanation of the code.

Source code

CMakeLists.txt

0# Copyright (C) 2024 Avular Holding B.V. - All Rights Reserved
1# You may use this code under the terms of the Avular
2# Software End-User License Agreement.
3#
4# You should have received a copy of the Avular
5# Software End-User License Agreement license with
6# this file, or download it from: avular.com/eula
7
8# Make rclcpp and used messages packages available
9find_package(rclcpp REQUIRED)
10find_package(sensor_msgs REQUIRED)
11find_package(ament_cmake REQUIRED)
12find_package(geometry_msgs REQUIRED)
13
14# Make the creos_sdk_msgs package available
15find_package(creos_sdk_msgs REQUIRED)
17# Create the creos_hello_world_ros executable target
20add_executable(creos_hello_world_ros main.cpp)
21# Link all dependencies to the creos_hello_world_ros executable
24ament_target_dependencies(creos_hello_world_ros
25 creos_sdk_msgs
26 rclcpp
27 sensor_msgs
28 geometry_msgs
29)

main.cpp

1// Copyright (C) 2024 Avular Holding B.V. - All Rights Reserved
2// You may use this code under the terms of the Avular
3// Software End-User License Agreement.
4//
5// You should have received a copy of the Avular
6// Software End-User License Agreement license with
7// this file, or download it from: avular.com/eula
8//
9/*****************************************************************************
10 * Simple hello world example for communicating with the CreOS SDK ROS2 node.
11 ****************************************************************************/
13#include <rclcpp/rclcpp.hpp>
14
15#include <geometry_msgs/msg/twist.hpp>
16#include <sensor_msgs/msg/nav_sat_fix.hpp>
17#include <sensor_msgs/msg/nav_sat_status.hpp>
18
19#include <creos_sdk_msgs/srv/enter_low_power_mode.hpp>
20
22
24class HelloWorldNode : public rclcpp::Node {
25public:
26 HelloWorldNode() : Node("hello_world") {
28
30 velocity_publisher_ = this->create_publisher<geometry_msgs::msg::Twist>(
31 "cmd_vel", rclcpp::QoS(10).best_effort().durability_volatile());
32 publishing_timer_ = this->create_wall_timer(std::chrono::milliseconds(1000), [this]() {
33 auto message = geometry_msgs::msg::Twist();
34 message.linear.x = 0.5;
35 message.angular.z = 0.5;
36 velocity_publisher_->publish(message);
37 RCLCPP_INFO(this->get_logger(), "Sent command velocity message");
38 });
40
42 gnss_subscriber_ = this->create_subscription<sensor_msgs::msg::NavSatFix>(
43 "gnss", rclcpp::QoS(10).best_effort().durability_volatile(),
44 [this](const sensor_msgs::msg::NavSatFix::SharedPtr msg) {
45 auto status = "UNKNOWN";
46 switch (msg->status.status) {
47 case sensor_msgs::msg::NavSatStatus::STATUS_NO_FIX:
48 status = "NO_FIX";
49 break;
50 case sensor_msgs::msg::NavSatStatus::STATUS_FIX:
51 status = "FIX";
52 break;
53 case sensor_msgs::msg::NavSatStatus::STATUS_SBAS_FIX:
54 status = "SBAS_FIX";
55 break;
56 case sensor_msgs::msg::NavSatStatus::STATUS_GBAS_FIX:
57 status = "GBAS_FIX";
58 break;
59 default:
60 break;
61 }
62 RCLCPP_INFO(this->get_logger(), "Received GNSS message: %s", status);
63 });
65
67 low_power_client_ = this->create_client<creos_sdk_msgs::srv::EnterLowPowerMode>("enter_low_power_mode");
68 auto request = std::make_shared<creos_sdk_msgs::srv::EnterLowPowerMode::Request>();
69 low_power_client_->async_send_request(
70 request, [this](rclcpp::Client<creos_sdk_msgs::srv::EnterLowPowerMode>::SharedFuture future) {
71 try {
72 auto response = future.get();
73 RCLCPP_INFO(this->get_logger(), "Low power mode entered: %s", response->success ? "true" : "false");
74 } catch (...) {
75 RCLCPP_ERROR(this->get_logger(), "Failed to enter low power mode");
76 }
77 });
78 };
79
81private:
82 rclcpp::Publisher<geometry_msgs::msg::Twist>::SharedPtr velocity_publisher_;
83 rclcpp::Subscription<sensor_msgs::msg::NavSatFix>::SharedPtr gnss_subscriber_;
84 rclcpp::Client<creos_sdk_msgs::srv::EnterLowPowerMode>::SharedPtr low_power_client_;
85 rclcpp::TimerBase::SharedPtr publishing_timer_;
86};
87
89int main(int argc, char* argv[]) {
90 rclcpp::init(argc, argv);
91
92 auto node = std::make_shared<HelloWorldNode>();
93 rclcpp::spin(node);
94
95 rclcpp::shutdown();
96 return 0;
97}
98
enter_low_power_mode.hpp
Interface definition of the creos_sdk_msgs/srv/EnterLowPowerMode service.
twist.hpp
Interface definition of the geometry_msgs/msg/Twist message.
geometry_msgs::msg::Twist
ROS message class definition for Twist.
Definition twist.hpp:15
sensor_msgs::msg::NavSatStatus::STATUS_GBAS_FIX
static const int8_t STATUS_GBAS_FIX
with ground-based augmentation
Definition nav_sat_status.hpp:30
sensor_msgs::msg::NavSatStatus::STATUS_SBAS_FIX
static const int8_t STATUS_SBAS_FIX
with satellite-based augmentation
Definition nav_sat_status.hpp:29
sensor_msgs::msg::NavSatStatus::STATUS_NO_FIX
static const int8_t STATUS_NO_FIX
unable to fix position
Definition nav_sat_status.hpp:27
sensor_msgs::msg::NavSatStatus::STATUS_FIX
static const int8_t STATUS_FIX
unaugmented fix
Definition nav_sat_status.hpp:28
nav_sat_fix.hpp
Interface definition of the sensor_msgs/msg/NavSatFix message.
nav_sat_status.hpp
Interface definition of the sensor_msgs/msg/NavSatStatus message.

Explanation

At the top of the main.cpp file, we include the necessary headers for the example. Specifically, we include rclcpp to interact with ROS2, and the necessary messages packages to communicate with the CreOS SDK ROS2 node. These also include the EnterLowPowerMode service type from the creos_sdk_msgs package.

13#include <rclcpp/rclcpp.hpp>
14
15#include <geometry_msgs/msg/twist.hpp>
16#include <sensor_msgs/msg/nav_sat_fix.hpp>
17#include <sensor_msgs/msg/nav_sat_status.hpp>
18
19#include <creos_sdk_msgs/srv/enter_low_power_mode.hpp>
20

For this example, we create a class that extends from rclcpp::Node. Most of our implementation will be inside this class' constructor.

24class HelloWorldNode : public rclcpp::Node {
25public:
26 HelloWorldNode() : Node("hello_world") {

We create a publisher that publishes geometry_msgs::msg::Twist messages to the cmd_vel topic. This message contains the linear and angular velocity of the robot. We also create a timer that triggers every second. In the callback of the timer, we create a geometry_msgs::msg::Twist message and publish it. Note that we match the Quality of Service settings with the settings used by the CreOS SDK ROS2 node, as specified in the Input Topics section.

30 velocity_publisher_ = this->create_publisher<geometry_msgs::msg::Twist>(
31 "cmd_vel", rclcpp::QoS(10).best_effort().durability_volatile());
32 publishing_timer_ = this->create_wall_timer(std::chrono::milliseconds(1000), [this]() {
33 auto message = geometry_msgs::msg::Twist();
34 message.linear.x = 0.5;
35 message.angular.z = 0.5;
36 velocity_publisher_->publish(message);
37 RCLCPP_INFO(this->get_logger(), "Sent command velocity message");
38 });

Next, we create a subscriber that subscribes to the gnss topic. In the callback of the subscriber, we extract the NavSatStatus from the received message, and print the status in a human-readable format. Note that we also match the Quality of Service settings here.

42 gnss_subscriber_ = this->create_subscription<sensor_msgs::msg::NavSatFix>(
43 "gnss", rclcpp::QoS(10).best_effort().durability_volatile(),
44 [this](const sensor_msgs::msg::NavSatFix::SharedPtr msg) {
45 auto status = "UNKNOWN";
46 switch (msg->status.status) {
47 case sensor_msgs::msg::NavSatStatus::STATUS_NO_FIX:
48 status = "NO_FIX";
49 break;
50 case sensor_msgs::msg::NavSatStatus::STATUS_FIX:
51 status = "FIX";
52 break;
53 case sensor_msgs::msg::NavSatStatus::STATUS_SBAS_FIX:
54 status = "SBAS_FIX";
55 break;
56 case sensor_msgs::msg::NavSatStatus::STATUS_GBAS_FIX:
57 status = "GBAS_FIX";
58 break;
59 default:
60 break;
61 }
62 RCLCPP_INFO(this->get_logger(), "Received GNSS message: %s", status);
63 });

We also create a service client that calls the enter_low_power_mode service. We immediately use this client to send an asynchronous request to the service. In the callback of the request, we print whether the transition to low-power mode was successful. If any exception has happened during the request, we print the failure to the console as well.

67 low_power_client_ = this->create_client<creos_sdk_msgs::srv::EnterLowPowerMode>("enter_low_power_mode");
68 auto request = std::make_shared<creos_sdk_msgs::srv::EnterLowPowerMode::Request>();
69 low_power_client_->async_send_request(
70 request, [this](rclcpp::Client<creos_sdk_msgs::srv::EnterLowPowerMode>::SharedFuture future) {
71 try {
72 auto response = future.get();
73 RCLCPP_INFO(this->get_logger(), "Low power mode entered: %s", response->success ? "true" : "false");
74 } catch (...) {
75 RCLCPP_ERROR(this->get_logger(), "Failed to enter low power mode");
76 }
77 });
78 };
79

In the main function, we simply create a new instance of our HelloWorldNode class and spin the node.

89int main(int argc, char* argv[]) {
90 rclcpp::init(argc, argv);
91
92 auto node = std::make_shared<HelloWorldNode>();
93 rclcpp::spin(node);
94
95 rclcpp::shutdown();
96 return 0;
97}
98
enter_low_power_mode.hpp
Interface definition of the creos_sdk_msgs/srv/EnterLowPowerMode service.
twist.hpp
Interface definition of the geometry_msgs/msg/Twist message.
geometry_msgs::msg::Twist
ROS message class definition for Twist.
Definition twist.hpp:15
sensor_msgs::msg::NavSatStatus::STATUS_GBAS_FIX
static const int8_t STATUS_GBAS_FIX
with ground-based augmentation
Definition nav_sat_status.hpp:30
sensor_msgs::msg::NavSatStatus::STATUS_SBAS_FIX
static const int8_t STATUS_SBAS_FIX
with satellite-based augmentation
Definition nav_sat_status.hpp:29
sensor_msgs::msg::NavSatStatus::STATUS_NO_FIX
static const int8_t STATUS_NO_FIX
unable to fix position
Definition nav_sat_status.hpp:27
sensor_msgs::msg::NavSatStatus::STATUS_FIX
static const int8_t STATUS_FIX
unaugmented fix
Definition nav_sat_status.hpp:28
nav_sat_fix.hpp
Interface definition of the sensor_msgs/msg/NavSatFix message.
nav_sat_status.hpp
Interface definition of the sensor_msgs/msg/NavSatStatus message.