Crazyflie

The Crazyflie platform flies Bitcraze Crazyflie 2.x nano quadcopters. It talks to them over a Crazyradio with the crazyflie_cpp library, and one node can fly a whole swarm. The Crazyflie runs its own estimator and controller, and Aerostack2 sends it velocity setpoints.

The Crazyflie needs a positioning deck or system to know where it is, such as a Flow deck, a Lighthouse system or motion capture. It can also carry a Multi-ranger deck and an AI deck camera.

Install

Set up the Crazyradio and the drones with Bitcraze's tools first:

1. Install cfclient and the Crazyradio udev rules it describes.
2. Update each Crazyflie's firmware from cfclient.
3. Give each Crazyflie its own radio address under Connect, Configure 2.x. Drones on the same radio channel need different addresses.

Then build the platform. The build downloads crazyflie_cpp if it isn't installed, so it needs internet access.

cd ~/aerostack2_ws/src
git clone https://github.com/aerostack2/as2_platform_crazyflie.git
cd ~/aerostack2_ws
rosdep install --from-paths src --ignore-src -y
colcon build --symlink-install --packages-up-to as2_platform_crazyflie

Launch

The swarm file lists the drones to fly, one namespace each with its radio URI:

/cf0:
  platform:
    ros__parameters:
      uri: "radio://0/80/2M/E7E7E7E701"

/cf1:
  platform:
    ros__parameters:
      uri: "radio://0/80/2M/E7E7E7E702"

ros2 launch as2_platform_crazyflie crazyflie_swarm_launch.py \
  swarm_config_file:=config/swarm.yaml

The launch starts one node that creates a platform for every namespace with a uri, so the same command flies one drone or many. Startup waits until every radio link connects, retrying every few seconds.

The platform configuration file applies to every drone, and the swarm file can override it per namespace:

Control modes

That fits the PID speed controller. There's no hover mode, so the controller holds the drone in place itself.

Topics

With the rest of the stack

With a Flow deck or Lighthouse, the Crazyflie's estimate is good enough to fly on. Use the raw_odometry estimator plugin on its odometry:

/**:
  state_estimator:
    ros__parameters:
      plugin_name: "raw_odometry"

With motion capture, use the ground_truth estimator on the mocap rigid body instead, and set external_odom to true. Each time a message arrives on external_odom_topic, the platform looks up the drone's pose in the TF tree and sends it to the Crazyflie's Kalman filter. Pointing that topic at self_localization/pose sends every new estimate.

AI deck camera

For a Crazyflie with an AI deck, add the camera's IP address to its namespace in the swarm file. The swarm launch then starts a node that streams the camera over Wi-Fi:

/cf0:
  platform:
    ros__parameters:
      uri: "radio://0/80/2M/E7E7E7E701"
  aideck_pub:
    ros__parameters:
      cam:
        ip: "192.168.4.1"
        port: 5000

Things to know

• Taking off and landing are done by Aerostack2's behaviors.
• Arming only marks the platform as armed. The motors start with the first command.
• Disarming and stopping the platform stop the motors. The kill switch sends the Crazyflie's emergency stop.
• The Crazyflie stops its motors by itself when setpoints stop arriving.

The project_crazyflie repository has a complete setup for one or several Crazyflies.