Hardware and software tutorials about flight controllers.
PX4 Research Log [10] – Adding a new flight mode (Preparation)
If you have programmed Ardupilot and now you switch to PX4, you would really appreciate how easy it is to implement a new flight mode in Ardupilot... PX4 is really good if you just want to write an App to do something, but implementing a new flight mode actually requires a lot of digging around