Adaptation from microRtps to XRCE-DDS

[mohamed1915]

Hello, I'm adapting a project that used Micro-RTPS to the new PX4 XRCE-DDS communication protocols. I used @Jaeyoung-Lim offboard example to solve some issues but other issues linger. The project runs multiple robots each uses PX4 with connection to gazebo and ROS2. I have few questions:

• With micro-RTPS we used a port for each robot, does XRCE-DDS needs the same thing?

-I have this error while the topics are published : [micro-ros-agent-7] Error while starting IPvX agent!. Does it mean it doesn't work?

• Is there any documentation for the migration to the new PX4, especially the communication part (RTPS->XRCE-DDS)?

• the node /px4_micro_xrce_dds is not connected to any part of ROS, it only generates the PX4 topics (fmu/in...or fmu/out....). I have publishers and subscribers in python that used to run on rtps, what changes do I need to make?

Thank you,

[mrpollo]

The documentation is still wip here's the discussion PX4/PX4-user_guide#2094 (review)

[Jaeyoung-Lim]

the node /px4_micro_xrce_dds is not connected to any part of ROS, it only generates the PX4 topics (fmu/in...or fmu/out....). I have publishers and subscribers in python that used to run on rtps, what changes do I need to make?

@mohamed1915 What is missing from https://github.com/Jaeyoung-Lim/px4-offboard ?

[beniaminopozzan]

@mohamed1915

With micro-RTPS we used a port for each robot, does XRCE-DDS needs the same thing?

It's not necessary to use different ports (which would require one Agent for each drone). You can use one agent, all clients with the same port but different session_key_id

PX4-Autopilot/src/modules/microdds_client/module.yaml

Lines 47 to 57 in fbc80c9

	XRCE_DDS_KEY:
	description:
	short: XRCE DDS key
	long: |
	XRCE DDS key, must be different from zero.
	In a single agent - multi client configuration, each client
	must have a unique session key.
	category: System
	type: int32
	reboot_required: true
	default: 1

[ViniciusAbrao]

Hi, let me include a question in this issue. Maybe if not related I can create a new one.

In XRCE-DDS client, looks like there is not a mission's service implemented yet. Also, I did not find any service as those implemented by mavros like: arm, set_mode, take off, land ....

Do you know something about it?

thank you

[mohamed1915]

@mohamed1915

With micro-RTPS we used a port for each robot, does XRCE-DDS needs the same thing?

It's not necessary to use different ports (which would require one Agent for each drone). You can use one agent, all clients with the same port but different session_key_id

PX4-Autopilot/src/modules/microdds_client/module.yaml

Lines 47 to 57 in fbc80c9

	XRCE_DDS_KEY:
	description:
	short: XRCE DDS key
	long: |
	XRCE DDS key, must be different from zero.
	In a single agent - multi client configuration, each client
	must have a unique session key.
	category: System
	type: int32
	reboot_required: true
	default: 1

Thank you @beniaminopozzan.

[mohamed1915]

Hi, let me include a question in this issue. Maybe if not related I can create a new one.

In XRCE-DDS client, looks like there is not a mission's service implemented yet. Also, I did not find any service as those implemented by mavros like: arm, set_mode, take off, land ....

Do you know something about it?

thank you

This is an interesting question. Because I also can't arm my drones in gazebo from ROS2 nodes. @Jaeyoung-Lim @beniaminopozzan do you have any ideas?
Thank you,

[ViniciusAbrao]

Hi, let me include a question in this issue. Maybe if not related I can create a new one.
In XRCE-DDS client, looks like there is not a mission's service implemented yet. Also, I did not find any service as those implemented by mavros like: arm, set_mode, take off, land ....
Do you know something about it?
thank you

This is an interesting question. Because I also can't arm my drones in gazebo from ROS2 nodes. @Jaeyoung-Lim @beniaminopozzan do you have any ideas? Thank you,

I have uploaded the code to include: arm, take off, offboard flight and land:

https://github.com/ViniciusAbrao/px4_ros2_xrcedds/blob/master/offboard_control.py