Yes, less code is awesome, bro. I'm just a beginner. The Multiwii firmware was written by many experts long time ago and Mahowik modified it to be able to build a self balancing robot with rich features with it and mahowik use PPM that is not available (Bluetooth module or PPM Receiver) with me now. So, I modified it to be able to use PWM with NRF24L01 and all works! But I want MORE. That's why, here, I got stuck when I add UBLOX GPS module in the firmware.