The Crazyflies have a radio bootloader pre-programmed. It allows to flash all firmwares over the air using Crazyradio. The boot loaders cannot erase themselves so it is always possible to restart the Crazyflie in bootloader mode.

For technical documentation go to:

• Bootloader protocol and architecture
• Bootloader client implementation

The bootloader can be entered in two ways: Cold-boot and warm-boot.

The procedure to cold-boot the bootloader depends of which Crazyflie you are using.

For Crazyflie 1 start the bootloading sequence on the PC and restrart the Crazyflie.

For Crazyflie 2, press the ON/OFF switch more than 1.5 second until the blue led blinks. Then release the button and the two blue leds should blink.

Warm booting is done when the Bootloader client restarts the Crazyflie in bootloader more automatically. While implemented in firmware this mode is not yet implemented in the PC client.