# MicroDDS Agent/MicroROS

## Introduction

{% hint style="success" %}
The following was user contributed content and edited by NXP. Note that there are several methods available for communication between ROS and PX4. This documents an established method.
{% endhint %}

## Setting up the MicroDDS Agent/MicroROS

One method used to communicate between the NavQPlus and the FMUK66v3 using T1 or Serial is by using MicroROS or the XRCE-dds Agent. \
\
To install these tools:

```
git clone https://github.com/eProsima/Micro-XRCE-DDS-Agent
cd Micro-XRCE-DDS-Agent
mkdir build && cd build
cmake ..
make
sudo make install
```

If using yocto, you can use the WIP meta package in your recipe.

```
https://github.com/dirksavage88/meta-dds
```

Alternatively, you can install micro-ROS through the ubuntu snap store

{% embed url="<https://snapcraft.io/install/micro-ros-agent/ubuntu>" %}
micro-ROS snap package
{% endembed %}

Another way to get micro-ROS is through Github as a ROS2 package. You can use the colcon build tools after sourcing the ROS setup.bash script in "/opt/ros/galactic/setup.bash"

{% embed url="<https://github.com/micro-ROS/micro_ros_setup.git>" %}
micro-ROS package
{% endembed %}

```
colcon build --symlink-install
```

Follow the instructions for each package on how to run the agent. The agent is a broker for clients on the network (including the FMUK66) and allows topics from the pixhawk to be shared with the DDS global space.

To set up the NavQ+, follow instructions in the Setup Guide -eMMC for a static IP. The FMUK66 is IP "10.0.0.1". As an example, you can set the NavQ+ to "10.0.0.3" with a blank ipv4.gateway (no quotes or anything) on Wired Connection 1.

Then start the microdds agent that is installed in the home directory in the Micro-XRCE-DDS-Agent build folder.

```
./MicroXRCEAgent udp4 -p 2019
```

On the FMUK66, ensure you have flashed to main and enter the following command.

```
microdds_client start -t udp -h 10.0.0.3 -p 2019
```

You should see the topic listed in the mavlink console after running the client start, as well as topic, publishers, data writers, and creators on the agent side.


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://nxp.gitbook.io/navqplus/user-contributed-content/ros2/microdds.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.