# 2021 培訓 ROS教學
###### tags: `教學`
## ROS簡介


* Source setup.bash

## 依檔案結構

### Workspace

http://wiki.ros.org/ROS/Tutorials/InstallingandConfiguringROSEnvironment#Create_a_ROS_Workspace

**1. 創建Workspace:**
`mkdir -p catkin_ws/src`
`cd catkin_ws/`
`catkin_make`

:::success
記得Source！！(最好加入.bashrc中)
:::

**2. Workspace 內容物:**

workspace_folder/        -- WORKSPACE
  build/
  devel/
  src/                   -- SOURCE SPACE

### Package

http://wiki.ros.org/ROS/Tutorials/CreatingPackage
http://wiki.ros.org/ROS/Tutorials/BuildingPackages

**1. 創建 Package**
`catkin_create_pkg test_pkg std_msgs rospy roscpp`
`cd "workspace_folder"`
`catkin_make`

**2. Workspace/src 放置Package**

workspace_folder/        -- WORKSPACE
  src/                   -- SOURCE SPACE
    CMakeLists.txt       -- 'Toplevel' CMake file, provided by catkin
    package_1/
      CMakeLists.txt     -- CMakeLists.txt file for package_1
      package.xml        -- Package manifest for package_1
    ...
    package_n/
      CMakeLists.txt     -- CMakeLists.txt file for package_n
      package.xml        -- Package manifest for package_n

**3. Package 內容物**

my_package/
  CMakeLists.txt
  package.xml
  src/
  (launch/)
  (msg/)
  ...

**4. package.xml**

<?xml version="1.0"?>
<package format="2">
  <name>test_pkg</name>
  <version>0.1.0</version>
  <description>The test_pkg package</description>

  <maintainer email="[e-mail]">Your Name</maintainer>
  <license>BSD</license>
  <url type="website">http://yourwebsite</url>
  <author email="[e-mail]">Jane Doe</author>
  
  <buildtool_depend>catkin</buildtool_depend>
  
  <build_depend>roscpp</build_depend>
  <build_depend>rospy</build_depend>
  <build_depend>std_msgs</build_depend>

  <exec_depend>roscpp</exec_depend>
  <exec_depend>rospy</exec_depend>
  <exec_depend>std_msgs</exec_depend>

</package>

**5. CMakeLists.txt**

## 依程式結構

### Node

http://wiki.ros.org/ROS/Tutorials/UnderstandingNodes


**1. 執行ROS的第一件事:** `roscore`

應該看到以下訊息:

... logging to ~/.ros/log/9cf88ce4-b14d-11df-8a75-00251148e8cf/roslaunch-machine_name-13039.log
Checking log directory for disk usage. This may take awhile.
Press Ctrl-C to interrupt
Done checking log file disk usage. Usage is <1GB.

started roslaunch server http://machine_name:33919/
ros_comm version 1.4.7

SUMMARY
======

PARAMETERS
 * /rosversion
 * /rosdistro

NODES

auto-starting new master
process[master]: started with pid [13054]
ROS_MASTER_URI=http://machine_name:11311/

setting /run_id to 9cf88ce4-b14d-11df-8a75-00251148e8cf
process[rosout-1]: started with pid [13067]
started core service [/rosout]

**2. rosnode**

`rosnode list`
`rosnode info`
`rosnode ping [node_name]`

**3. 執行node**
`rosrun [package_name] [node_name]`
### Topic

http://wiki.ros.org/ROS/Tutorials/UnderstandingTopics

1. **rostopic**

1. `rostopic list`
2. `rostopic echo`
3. `rostopic type`
4. `rostopic pub`

2. **rqt_graph**


### Message

http://wiki.ros.org/ROS/Tutorials/CreatingMsgAndSrv

1. 各個 message type: http://wiki.ros.org/std_msgs
2. `rosmsg show [message type]`

## RIVZ

* 啟動rivz: `rviz`


## Roslaunch

http://wiki.ros.org/ROS/Tutorials/UsingRqtconsoleRoslaunch

## Publisher & Subscriber

### Python

http://wiki.ros.org/ROS/Tutorials/WritingPublisherSubscriber%28python%29

#### Publisher:

#!/usr/bin/env python

import rospy
from std_msgs.msg import String

def talker():
    pub = rospy.Publisher('chatter', String, queue_size=10)
    rospy.init_node('talker', anonymous=True)
    rate = rospy.Rate(10) # 10hz
    while not rospy.is_shutdown():
        hello_str = "hello world %s" % rospy.get_time()
        pub.publish(hello_str)
        rate.sleep()

if __name__ == '__main__':
    try:
        talker()
    except rospy.ROSInterruptException:
        pass

#### Subscriber:

#!/usr/bin/env python

import rospy
from std_msgs.msg import String

def callback(msg):
    rospy.loginfo(msg.data)

def listener():

    rospy.init_node('listener', anonymous=True)

    rospy.Subscriber('chatter', String, callback)

    rospy.spin()

if __name__ == '__main__':
    listener()

#### 又接又丟的Node

#!/usr/bin/env python3

import rospy
from std_msgs.msg import Int64, String

class Auv(object):
    def __init__(self):
        self.pub = rospy.Publisher('Result', String, queue_size = 10)
    def odd_or_even(self, value):
        if (value.data % 2) == 0:
            result = 'Even'
            self.pub.publish(result)
        else:
            result = 'Odd'
            self.pub.publish(result)
            
def listener():
    rospy.init_node('test_sub', anonymous=True)
    auv = Auv()
    rospy.Subscriber('test', Int64, auv.odd_or_even)
    rospy.spin()
    
if __name__=='__main__':
    listener()

### C++

http://wiki.ros.org/ROS/Tutorials/WritingPublisherSubscriber%28c%2B%2B%29

#### Publisher:

#include "ros/ros.h"
#include "std_msgs/Int64.h"

int main(int argc, char **argv)
{
        int x = 9;
        std_msgs::Int64 x_topic;
        ros::init(argc, argv, "cpp_pub_test");
        ros::NodeHandle node;
        ros::Publisher pub = node.advertise<std_msgs::Int64>("cpp_test", 1000);
        ros::Rate r(1);

        while (ros::ok())
        {
                x = (x + 1) % 5;
                x_topic.data = x;
                pub.publish(x_topic);
                ros::spinOnce();
                r.sleep();
        }
        return 0;
}

#### Subscriber:

#include "ros/ros.h"
#include "std_msgs/Int64.h"

void odd_or_even(const std_msgs::Int64::ConstPtr& n_topic)
{
        if (n_topic->data % 2)
                ROS_INFO("%s", "Odd");
        else if (!(n_topic->data % 2))
                ROS_INFO("%s", "Even");
}

int main(int argc, char **argv)
{
        ros::init(argc, argv, "cpp_sub_test");
        ros::NodeHandle node;
        ros::Subscriber sub = node.subscribe("cpp_test", 1000, odd_or_even);

        ros::spin();

        return 0;
}

#### How to Build

To build the package (and the cpp node), follow the steps below:
1. **Add "genmsg" into `find_package`**
2. **Uncomment all part in `generate_messages`**
3. **Uncomment (or write it yourself) `add_executable(*nodename* *src/scriptfilename(.cpp file)*)`**
4. **Uncomment (or write it yourself) `target_link_libraries(*nodename* ${catkin_LIBRARIES})`**
5. **Do step 3&4 for each cpp file**
6. **`catkin_make`**

<br>

**CMakeLists.txt in the package:**

cmake_minimum_required(VERSION 3.0.2)
project(cpp_test)

find_package(catkin REQUIRED COMPONENTS
  roscpp
  rospy
  std_msgs
  genmsg
)

generate_messages(
   DEPENDENCIES
   std_msgs
 )

catkin_package()
include_directories(include ${catkin_INCLUDE_DIRS})

add_executable(${PROJECT_NAME}_pub src/pub.cpp)
target_link_libraries(${PROJECT_NAME}_pub ${catkin_LIBRARIES})

add_executable(${PROJECT_NAME}_sub src/sub.cpp)
target_link_libraries(${PROJECT_NAME}_sub ${catkin_LIBRARIES})