How to enable PPM

[highfreq]

Could someone please write clearly what needs to be done to receive ppm?
I have seen the post on ardupilot discuss but it is far from being clear.

Please post what lines to modify before recompiling and where the ppm line will connect on the Obal. It was not clear to me if the serial port would be used, in that case the gps serial must be added somewhere else i guess with an usb serial adapter or something similar.

[highfreq]

I found your youtube tutorial, modified the files and recompiled, everything ok. What is not clear to me is what is the pin to use now for PPM (i left gpio 5).
Do i have to use gpio 5 on the raspberry to inject ppm?

[highfreq]

Would it be asking too much to have the steps needed for ppm documented in wiki instead of having to find a youtube video for the file mods needed?
Still not understand what pin to use for ppm input, i guess it is gpio 5.