将本机DDS系统与ROS2接口 [英] Interfacing a native DDS system with ROS2
问题描述
要与基于ROS2的发布者和基于RTI Connext的订户进行通信，它们两者都需要具有兼容的QoS设置。
To communicate to a ROS2 based publisher and a RTI Connext based subscriber, both of them need to have a compatible QoS settings.
我正在使用RTI Connector for python并使用XML Application Creation运行订户。
I am using RTI Connector for python and using the XML Application Creation to run the subscriber.
我在ROS2中运行了 talker_py ，其中默认并订阅以下消息RTI Connext Pro。
I run a talker_py in ROS2 which has a default QoS and subscribe to these messages in RTI Connext Pro.
ROS2 IDL看起来像这样：
The ROS2 IDL is looks like this :
{
module msg
{
module dds_ {
struct String_ {
String data_;
};
};
};
};
我使用 rtiddsgen 实用工具进行转换将其转换为XML文件。这是转换后的XML：
I use the rtiddsgen utility tool to convert it into a XML file. Here is the converted XML :
<?xml version="1.0" encoding="UTF-8"?>
<types xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="/path/to/RTIInstall/rti_connext_dds-5.3.1/bin/../resource/app/app_support/rtiddsgen/schema/rti_dds_topic_types.xsd">
<module name="std_msgs">
<module name="msg">
<module name="dds_">
<struct name="String_">
<member name="data_" type="string"/>
</struct>
</module>
</module>
</module>
</types>
我在< types> 中添加了我的 USER_QoS.xml ，看起来像是：
I added the <types> to my USER_QoS.xml and it looks like :
<dds xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:noNamespaceSchemaLocation="http://community.rti.com/schema/5.1.0/rti_dds_profiles.xsd" version="5.1.0">
<!-- Qos Library -->
<qos_library name="QosLibrary">
<qos_profile name="DefaultProfile" is_default_qos="true">
<datawriter_qos>
<history>
<kind>KEEP_LAST_HISTORY_QOS</kind>
<depth>1000</depth>
</history>
<reliability>
<kind>RELIABLE_RELIABILITY_QOS</kind>
</reliability>
<durablitiy>
<kind>VOLATILE_DURABILITY_QOS</kind>
</durablitiy>
</datawriter_qos>
<participant_qos>
<transport_builtin>
<mask>UDPV4 | SHMEM</mask>
</transport_builtin>
<!-- Turn on monitoring -->
<!-- Begin Monitoring
<property>
<value>
<element>
<name>rti.monitor.library</name>
<value>rtimonitoring</value>
</element>
<element>
<name>rti.monitor.create_function_ptr</name>
<value>$(NDDS_MONITOR)</value>
</element>
</value>
</property>
End Monitoring -->
</participant_qos>
</qos_profile>
</qos_library>
<!-- types -->
<types>
<module name="std_msgs">
<module name="msg">
<module name="dds_">
<struct name="String_" extensibility="extensible">
<member name="data_" type="std_msgs::msg::dds_::string" "/>
</struct>
</module>
</module>
</module>
</types>
<!-- Domain Library -->
<domain_library name="MyDomainLibrary">
<domain name="MyDomain" domain_id="0">
<register_type name="std_msgs::msg::dds_::String_" type_ref="std_msgs::msg::dds_::String_" />
<topic name="chatter" register_type_ref="std_msgs::msg::dds_::String_"/>
</domain>
</domain_library>
<!-- Participant library -->
<domain_participant_library name="MyParticipantLibrary">
<domain_participant name="Zero" domain_ref="MyDomainLibrary::MyDomain">
<subscriber name="MySubscriber">
<data_reader name="MyChatterReader" topic_ref="chatter" />
</subscriber>
</domain_participant>
</domain_participant_library>
</dds>
现在，当我将RTI连接器用于python时，此处的第一步是尝试加载 USER_QoS.xml 文件，它始终显示错误无法解析.xml文件。我强烈认为这是因为在< types> 定义中存在关键字 module 。
Now when I use the RTI Connector for python, the first step here is trying to load the USER_QoS.xml file and it always give the error Unable to parse the .xml file. I strongly feel that this is because of the presence of the keyword module in the <types> definition.
这是RTI连接器的python脚本：
Here is the python script for the RTI Connector:
from __future__ import print_function
from sys import path as sysPath
from os import path as osPath
from time import sleep
filepath = osPath.dirname(osPath.realpath(__file__))
sysPath.append(filepath + "/../../../")
import rticonnextdds_connector as rti
connector = rti.Connector("MyParticipantLibrary::Zero",
filepath + "/../User_QoS.xml")
inputDDS = connector.getInput("MySubscriber::MyChatterReader")
for i in range(1, 500):
inputDDS.take()
numOfSamples = inputDDS.samples.getLength()
for j in range(1, numOfSamples+1):
if inputDDS.infos.isValid(j):
# This gives you a dictionary
sample = inputDDS.samples.getDictionary(j)
x = sample['x']
# Or you can just access the field directly
toPrint = "Received x: " + repr(x)
print(toPrint)
sleep(2)
我觉得连接器无法解析此 module 关键字。可能是这样吗？
I feel that the connector is not able to parse this module keyword. Could it be the case ?
推荐答案
当我尝试进行设置时，连接器提供的输出比您指定的还要多。
When I try your setup, Connector provides more output than what you have indicated. Among others:
RTIXMLParser_validateOnStartTag:Parse error at line 15: Unexpected tag 'durablitiy'
这是XML中的错误，根据其架构，标记名称应为耐久性。
This is an error in your XML, according to the its schema the tag name should be durability.
然后，您似乎在复制生成的< types> 标记及其标签时出现了复制粘贴错误。内容转换为XML。为此，连接器给出以下错误：
Then you seem to have made copy-paste errors copying the generated <types> tag and its contents into your XML. For that, connector gives the following error:
RTIXMLParser_parseFromFile_ex:Parse error at line 50: not well-formed (invalid token)
实际上，您的第50行结尾处有多余的报价：
Indeed your line 50 has a superfluous quote at the end:
<member name="data_" type="std_msgs::msg::dds_::string" "/>
此外， type 属性的值与您尝试生成的XML不同在此处插入，其中包含：
Also, the value of the type attribute is different from the generated XML that you tried to insert here, which has:
<member name="data_" type="string"/>
更正这些错误后，Connector会正确实例化。
After correcting those errors, Connector instantiates properly.
到根据其架构验证XML文件，您可以/应该使用关联的XSD架构定义。
To validate your XML file against its schema, you can/should use the associated XSD schema definition.
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