Plane v3.8 apparently removed the RCx_FUNCTION params. They dont appear anymore. How can we setup a camera so that the pix triggers it?
There are now SERVOx_FUNCTION params for that. I believe that will get you what you are looking for. http://ardupilot.org/plane/docs/parameters.html#servo2-function-servo-output-function
I finally got it to work, the detail was not in the settings but on pressing the damn SAFETY SWITCH!!!!
Ah yes, there is a parameter that lets you specifiy what channels ignore the safety switch. It's a bit of a pain but with it you can make it so the plane can take photos regardless of being armed or not. http://ardupilot.org/plane/docs/parameters.html#brd-safety-mask-channels-to-which-ignore-the-safety-switch-state is the controlling parameter.
@tridge this probably belongs in that migration guide as a note for camera users. Although I'm not sure if this was a 3.7 or a 3.8 change. (I've been using it for so long I can't recall at this point)