If you already own a Taranis 9x (Pro) RC transmitter and want to use it as a controller, it can be configured to work with the Crazyflie Android client.

Fortunately the transmitter is able to act as an USB Joystick (see https://github.com/opentx/opentx/wiki/OpenTX-USB-Joystick), but first you need to create a new model for this configuration:

• you can turn off both internal and external TX modules
• you need to configure the thrust input (Weight 50% and Offset 50%)
  • otherwise you can not use the full travel of the axis assigned to thrust
• Servos menu
  • invert Thrust (CH1)
  • invert Eleron (CH3)

You can also download the configuration as an EEPE file and install it with the OpenTX Companion application.

• USB Joystick EEPE file: usbjoystickforandroidcfclient.eepe.zip
• Download the Companion application here: http://www.open-tx.org/2015/05/04/opentx-2.0.17