I've written a little Arduino Sketch that allows using a Saitek X52 (Pro) Joystick to generate a CPPM signal that can be fed to most common RC transmitters to control my Quanum Trifecta Tricopter. To connect to the joystick the Arduino USB Host Shield is used.
Get all the code on GitHub: https://github.com/xythobuz/Saitek-X52-PPM
A full writeup can be found on my website: http://xythobuz.de/2016_07_24_usb_host_cppm.html
Be aware that this video really shows how bad the Saitek X52 is able to control the Copter. The problem is the low sensitivity and very high deadzone of the Joystick compared to common RC transmitters. This may be mitigated slightly by modifying the sensors in the joystick, but I haven't tried this.
Of course my code can easily be adapted to work with other controllers that may offer more sensitivity.