Fast camera trigger capture in master

Hi, I am asking here because there is no documentation on how this feature works.

I have PLANE 3.7.1 - two pixhawk 2.4.6 clone and another original doing same thing

My circuits use 5V from the rail and thanks to a photodiode reading my Canon LED, feeds from 0V to 5V to the CAM_FEEDBACK_PIN, it doesn’t works so I removed the circuit and measured what happens to the CAM_FEEDBACK_PIN and:

when the pin is set as CAM_FEEDBACK_PIN and at least one picture is taken, the pin begins to feed 3.3V and stays on until lipo remove, so reconnect lipo, arm, do the shutter commands and again 3.3V back, I don’t know if it’s a bug or my fault, I made a video here CAM_FEEDBACK_PIN output 3.3V when it should not
Thank you