@MasK
easy part first: The swc programming doesn't apply when using canbus instead of key1/key2. There's a setting to flip the controls if they're swapped. It's under factory settings (pin 3368), then something like car agreement (can't remember the actual name).
What car is this? If you have a traditional resistor network style steering wheel wire, you may be able to use that instead and program as desired.
I haven't tested canbus yet (my car doesn't have canbus leads in the radio harness, so I'll have to tap it from somewhere else).
You wired your camera power to the reverse light? In that case, you can splice it to the power wire that's married to the composite cable and hook it up to the "back" wire on the headunit harness. That'll trigger it outside canbus.
Or you can tap the same reverse wire up front to "back", and hook up cam 12v to power the cam instead (doesn't really make a difference though since I don't know if there's a way to force the reverse camera when not in gear).
As far as utilizing canbus for reverse, you can try checking in factory settings that the proper canbus config has been applied. Or you might need to find the manual for your canbus decoder. My unit came with one (a raise box for mazda), and it seems to provide a reverse out pin. So I'm not sure if the headunit would directly be able to pick up reverse via canbus, or if I'd need to add a wire to connect that pin to "back" (no matter since I already tapped a reverse source). Curious since I haven't been able to find a canbus message for reverse for my car anyway (seemingly only in-gear or not).
I did notice a reverse power setting, but haven't checked what it does. I have it disabled, but when going in reverse, it does provide 12v. Maybe it'd reverse it to ground instead?
So if you verify the canbus settings to be proper on the headunit, you might need to fall back to using the "back" wire to trigger instead.
* check if your canbus decoder has a pin for reverse and it works as expected
* find a reverse source under the dash and tap that
* feed the reverse signal back up via the composite/power combo wire since you've already got it tapped
First two options would let you use the headunit to supply power to the cam and undo the reverse tap in the reaer.
Curiously, I get some group loop interference if I connect the cam to ground. If I leave it floating, and just rely on the composite cable's ground to