No way to make relay or camera trigger working on the Pixracer FC - almost solved!

I’m using a Pixracer controller on my plane, for some other compatibility problems with higher version I’m still using plane 4.0.9.
For already two days I’m trying to configure any free output to trigger my camera recording.
I need only logical HIGH and LOW levels according the position of the switch on my radio (NOT a PWM signal). No need any big power, really only simple logical levels on an CPU output.
As described here I want to use RC10 channel to control the output so I set RC10_OPTION to 28 (relay on/off).
For output I want to use e.g. unused GPIO 61 (intended for 8266_GPIO0 as referenced here) so I set RELAY_PIN to 61.
After settings and reboot at the pin there is permanent logical HIGH which doesn’t change on RC10 channel change nor if I try to control it from Mission Planner via tab Data / Servo/Relay.

I tested to get similar functionality via “camera trigger” setting as described here and reached PWM signal changing on a PWM out according to the switch position, but when I tried to change it to “relay”, it didn’t work.
Documentation is not very clean regarding this topic and mostly refers to the older Pixhawk FC so I’m lost.
Can please someone propose me the simplest working solution?

Made it working some way setting camera trigger source RC10_OPTION to 9, CAM_TRIGG_TYPE to1 and RELAY_PIN to 61.
Still not understand why RC10_OPTION 28 didn’t work. I’d need one more relay working to another switch so I’ll keep playing with it…

Today I made relay working - really don’t know what was incorrect before :roll_eyes:. Only one problem remains: Can be relay or it’s control channel software reversed? I need to have opposite relay GPIO levels, than standard.
If control channel is 1000-1500, relay GPIO should have HIGH level. If input is 1501-2000, output should have LOW level. Seems easy to use hardware invertor, but between power up and full boot (some seconds) has GPIO anyway HIGH level and if HW inverted, it triggers my camera.
Also reversing control channel in settings doesn’t help and reversing in TX is not a way for me as I use the same channel also for switching cameras (bypassing FC) and want to have the same layout for all planes.
Is there any chance to reverse relay operation only?
Sorry, I know it’s really a very specific complicated case…