I installed one of these last week. Works great. (Bought from Halfords in the UK, shipped down to Spain and installed myself)
Still learning the ins and outs but so far it does everything I need.
However, I installed a good quality reversing camera today and have a problem that I'm hoping someone on here can help me with. (I've been searching the web like crazy this afternoon but none of the work arounds seem to be working for me!)
I wired it up as follows:
Camera + to reverse light +
Camera - to ground. (camera works. so far, so good)
HU reverse input to reverse light + (Spliced into reverse light +, along with the camera +)
Camera Video output to HU video input.
HU handbrake sensor wire to ground to fool the HU into thinking the handbrake is on.
Heres the problem. When engaging reverse, the HU display instantly switches to a black blank screen with the usual warning "screen images may be reversed". I press the "X" and the screen instantly reverts back to whatever was displayed prior to engaging reverse, instead of going to the reverse camera input display.
If I'm in app mode I then press "mode" and then "AV" and then "AV" and up comes the rear view camera display perfectly.
Car play mode is the same with an additional step "Pioneer Home" to get to the app mode menu.
Heres the thing..........I was expecting the rear view display to come up automatically without having to press the additional menu buttons!
So, is this normal or have I messed up the wiring?, or is there a hidden menu option I haven't found?, or is the handbrake sensor ground messing things up?
I've been through all the possible menu settings and nothing makes any difference so far.
Its the same whether in carplay or app mode.
I'm really hoping I've made a mistake somewhere because having to scroll through menus to get the rear view image every time I engage reverse is a right royal pain in the ass!
Any help and advice would be greatly appreciated as its driving me nuts! 
Many Thanks in advance 