The code is all contained in a single .ino file. Open it in the Arduino IDE, install Teensyduino, and upload it. That is all. The PID control loop, attitude estimation using a complementary filter, ...
Have you ever bought a $700 transmitter? A Futaba 10PX. A SANWA M17. The moment you touch it, you think, 'This is it.' The precision of the sticks, the response, the way it feels in your hands. It is ...