Christmas is getting close, and while most people are just starting to hang lights and decorate their tree, we decided to go a little bigger and a whole lot brighter. Instead of adding tinsels and ornaments, we set up a swarm of 8 Crazyflie 2.1 Brushless drones with the upcoming Color LED decks along with some long-exposure photography magic, and decorated our flying arena with a Christmas tree made of Crazyflies.
How it works
The project is split into two parts: the firmware side that controls the Color LED decks and the script that is responsible for the choreography of the swarm.
The Firmware
Instead of lighting the LEDs based on time or commands, each Crazyflie uses its 3D position to decide on the correct color. This makes the whole communication with the central computer easier. Inside the firmware, multiple virtual spheres are created in the flight arena, just like ornaments floating in a tree-shaped structure. Whenever a Crazyflie flies into one of these spheres, its Color LED deck switches instantly from green to red. When it flies back out, it glows green again. Since we’re taking a long-exposure photo, the whole color pattern begins when the drones are ready to perform the choreography and stops when they start landing.
The Script
The python script is pretty simple. It commands a swarm of Crazyflies to perform a coordinated spiral choreography resembling a Christmas tree outline in 3D space. Each drone takes off to a different height, flies in spiraling circular layers, and changes radius as it rises and descends, forming the visual structure of a cone when viewed from outside. To pull this off with the current state of the cflib, we used 3 Crazyradios 2.0 and the high level commander.
A Testbed for Crazyradio 2.0 Improvement
Lately, we have been looking again at improving the radio communication with the Crazyflie. A prototype featuring a new USB communication mode for the Crazyradio was ready just in time for testing with the Christmas tree demo.
This new mode makes Crazyradio 2.0 much more efficient when communicating with swarms. With it, we were able to fly the same demo using only one Crazyradio 2.0 instead of 3 with the connection time to the swarm greatly accelerated. This demonstrates the efficiency of the new mode.
The new mode is called “inline setting mode” since it works by inlining all radio settings with the packet data, negating the need to issue time-costly USB setup requests. It is currently a Pull Request to Crazyradio 2.0 and the Rust Crazyradio driver. Support for Crazyswarm/ROS and CFLib will be implemented and when we know that the protocol works out for all libs, we will merge and release support for the new mode. It will be enabled by default so you will get the benefits from upgrading the Crazyradio 2.0 firmware and lib. We will talk more about it when it is released, in the mean time do not hesitate to test and feedback on the PRs ;-).
Demo source code
You can find the project’s repository as well as the rust version on Github. The python version was used for the picture and video, and the Rust one behaves identically.