Hark > Packages > HARK-ROS > HARK-ROS Tutorials > Publishing/Subscribing msg type Topics

Publishing/Subscribing msg type Topics

Main Sheet Configuration

  • Required Modules
    • RosNodeGenerator
    • LOOP0 (This appears after you create iterator sheet.)

 

RosNodeGenerator

  • Module Description

This module generates a ROS node with a specific node name defined by NODE_NAME property.

Since ROS allows single node generation for single process, DO NOT put this node more than two in the same HARK network file.

 

  • Module Location
Node list > HARK:ROS:Master > RosNodeGenerator

 

  • Property settings
Name Type Value Explanation
NODE_NAME string HARK_MASTER_NODE ROS node name for this network file.

 

HARK_MASTER_NODE is just an example. You can give any preferred ROS node name.

  • Terminal settings

 

Set “VALUE” for this output.

 

LOOP0

Set “OUTPUT1” and “OUTPUT1_2” for this outputs after iterator sheet configuration.

 

 Iterator Sheet Configuration

  • Required Modules
    • Sleep
    • RosHarkIntPublisher
    • RosHarkIntSubscriber

 

Sleep

  • Module Description

This module outputs true with a certain sleep time.

 

  • Module Location
Node list > Flow > Sleep

 

  • Property settings
Name Type Value Explanation
SECONDS float 2 Interval sleep time to output TRUE.

 

  • Terminal settings

Set “CONDITION” for this output. Then, this whole network file runs with a sampling time of the sleep time.

 

RosHarkIntPublisher

  • Module Description

This module publishes a HarkInt type (contains just an integer) topic.

The value of the integer is determined as “count + PARAM”.

 

  • Module Location
Node list > HARK:ROS:Sample > RosHarkIntPublisher

 

  • Property settings
Name Type Value Explanation
TOPIC_NAME string HarkInt1 Published ROS Topic Name
BUFFER_NUM int 100 Number of buffers for published messages.
PARAM int 0 Output integer setting

 

  • Terminal settings

Set “OUTPUT1” for this output.

 

RosHarkIntSubscriber

  • Module Description

This module subscribes a HarkInt type (contains just an integer) ROS topic.

It displays and outputs the integer.

 

  • Module Location
Node list > HARK:ROS:Sample > RosHarkIntSubscriber

 

  • Property settings
Name Type Value Explanation
TOPIC_NAME string HarkInt1 Subscribed ROS Topic Name
BUFFER_NUM int 100 Number of buffers for subscribed messages.
ROS_DURATION float 0.001 Minimum interval of ROS topic subscription.

 

ROS_DURATION is only valid if the ROS_DURATION is longer than HARK interval.

Set ROS_DURATION small value so that HARK can work with desired interval.

 

  • Terminal settings

Set “OUTPUT1_2” for this output.

 

 Examining the network file

Save the network file before closing [e.g.) RosHarkInt_Publisher_and_Subscriber.n ]

Open a new terminal and type

roscore

 

Go back to the previous terminal and run the HARK network file

./RosHarkInt_Publisher_and_Subscriber.n

 

You’ll see something like following.

node_RosHarkIntPublisher_1 constructor end... 
node_RosHarkIntSubscriber_1 constructor end...
ROS node : HarkRosMasterNode generated...
node_RosHarkIntPublisher_1 initialized...
node_RosHarkIntSubscriber_1 initialized...
ROS initialized...
<Int 0 >
node_RosHarkIntPublisher_1 Published : [0]
node_RosHarkIntSubscriber_1 Subscribed : [0] [ INFO] [1289788809.709227278]: Received [0] [thread=0x8ecd528] 
node_RosHarkIntPublisher_1 Published : [1]
node_RosHarkIntSubscriber_1 Subscribed : [0] [ INFO] [1289788809.874858947]: Received [1] [thread=0x8ecd528]
node_RosHarkIntPublisher_1 Published : [2]
node_RosHarkIntSubscriber_1 Subscribed : [1] [ INFO] [1289788810.048147291]: Received [2] [thread=0x8ecd528]

 

If you see some ROS related errors in the standard output, type

. ~/ros/setup.sh

on your terminal to refresh ROS related environmental variable settings.

Now, let us check how the ROS system sees the HARK network by rqt_graph.

rosrun rqt_graph rqt_graph

 

You can see that the HARK network file successfully creates the HARK_MASTER_NODE node.

Also, the HarkInt1 topic is published/subscribed by the node.

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