Overview

This page will explain the overview of the crazyflie ROS 2 nodes:

Explanation per package

In the source code of the Crazyswarm2 (Crazyflie ROS 2) project, there are several packages that we will explain here:

crazyflie/: The package that contains the crazyflie server nodes and the crazyflies.yaml.
crazyflie_py/: The package that contains the python library that wraps around the ROS 2 services and topics that connects with the crazyflie server nodes.
crazyflie_examples/: The package that contains examples of using the crazyflie ROS 2 package. See ROS 2 Tutorials.
crazyflie_interfaces/: The package that contains all msgs and srvs for the crazyflie ROS 2 project.
crazyflie_sim/: The package that contains our simulator.

Crazyflie server

The crazyflie server node connects multiple Crazyflies with on or more Crazyradio PA dongles.

It has three backends that you can choose from:

cpp: This is based on the crazyflie-link-cpp on the lowest layer.
cflib: This is based on the crazyflie-lib-python up until the logging, parameter, and command sending handling.
sim: Our simulator behaves like a regular backend, offering ROS 2 topics and services, see below for more details on the simulation.

It handles several low level communication aspects with the Crazyflies:

Parameter to ROS 2 parameters handling: It receives the parameter ToC from the Crazyflie, transforms it into ROS 2 parameters, and sets the CF2 parameters based on the crazyflies.yaml input.
Logging to ROS 2 topics handling: The server sets up logblocks for data streaming in the crazyflie, and transforms the received variables into ROS 2 topics.
Run-time configuration: Both parameters and logging can be configured in run-time while the server is connected with the Crazyflies. Please check Usage.

It also setups several flight command services:

Takeoff / Land / GoTo: With a single service command and a given height or coordinate, you can make the connected crazyflies take off, go to a position and land.
Upload / Start trajectory: You can upload a predefined trajectory and indicate if the Crazyflies need to start flying it.
Emergency : To turn off the motors in case something goes wrong.
/all or /cf2 : The services are setup either for all crazyflies to respond to, or each individual crazyflie, depended on the prefix.

Simulation

The simulator uses the Crazyflie firmware as a software-in-the-loop (SIL). It provides the same ROS interface as the server and therefore can be used with C++ or Python user code.

Currently, the desired setpoint is visualized in rviz (see Usage) or a simple physics-based simulator can be used.

Support functionality with backends

Functionality	Cpp	CFlib	Sim
Parameters	Yes	Yes	No
Logging
default: pose	Yes	Yes	No
default: scan	Yes	Yes	No
default: odom	No	Yes	No
default: status	Yes	Yes	No
custom	Yes	Yes	No
Add/Remove Srv	No	Yes	No
Broadcasts	Yes	No	n/a
Manual control
cmd_full_state	Yes	Yes	Yes
cmd_position	Yes	No	No
cmd_hover	No	Yes	No
High-level control
takeoff/land	Yes	Yes	Yes
go_to	Yes	Yes	Yes
upload/start traj	Yes	Yes	Yes
Positioning System
Motion Capture	Yes	Yes	No
Flow Deck	Yes	Yes	No
LightHouse	Yes	Yes	No
LPS	Yes	Yes	No
Misc
Arming	Yes	Yes	n/a