Good news is that CC3D does support PPM input, and the nice thing about PPM is that it only required one cable.
All you need to do is connect the PPM signal from your R/C receiver to the 3rd pin on cc3d (as the first two are for ground and power)
And then its just a matter of setting it up on the software to tell it you are using PPM unput. If you are using cleanflight you need to do the same thing, but the menu is in a different place since its a different firmware..
Hope that helps