Output/aux pixhawk problem

hello, I’d like to take pictures with my drone camera. I connected the camera switch to the ground and to the AUX 2 - CH10 signal (I have a frsky x8r receiver in SBUS - 16ch) of the pixhawk 2.4.8.
I did tests by setting SERVO10_FUNCTION on values 10 (trigger camera), 1 (rc passthrough) and SERVO10_OPT on “camera trigger”. The result is that with the radio switch at rest, between signal and ground I have 0.15v while with the radio switch pressed I have 0.32v. This way I can’t trigger the camera. Theoretically I should have a voltage of 0 - 5v (0-3.3v) between the minimum and maximum value of the pwm, right? could anyone help me? thank you