So, can it be controlled directly by the PWM width from the radio? Only to connect it to the servo output, set RCPassThru, set the 3-pos. switch and it should work, am I right?
I think it just wants GPIO. So attach the pin to a motor output, select that motor function as GPIO and then select a RELAYx_PIN to point to that pin (look in hwdef for the GPIO pin number). You can then use the RELAY RC option to switch it. That’s the basic approach, but you will need to do some digging to see whether you can get it to work …
OK, thank you very much, I got it. I set a switch on radio ch.7, then I set RC7_OPTION=34 (relay2 on/off), the camera remote control pin was connected to SERVO13 (function set to -1) and RELAY_PIN2=62 (S13 for H743). It is possible by the switch (0.3-1s pulses) to take pictures or turn on/off the video, but I did not succeed to flip between photo and video mode.
I just found this protocol for the remote control of Runcam 2 4K camera:
One 85 ms pulse switches the camera from Video recording mode to Photo mode.
Two 85 ms pulses with a gap of 85ms start / stop a video recording or take a picture in photo mode.
So, I guess such protocol is currently not available in AP. The only option is to do it with a separate microcontroller or with a discrete scheme. I checked the protocol by a signal generator and it seems it is working like described.
There is a cable for such function produced by Runcam, but currently it is not available anywhere.
I tried to setup this relay switch on a different servo output (S12), and it did not work. Finally I found out (by a uC switcher connected between S7, PWM and camera input), that this camera needs an inverted signal and an open collector (normally 3.3V from turned-on camera and 0V for triggering, 0.3-1s set in the radio. So, in my previous input described protocol from somebody, with normally 0V has a mistake. It needs to be inverted.
I still don’t understand, how it can work on the LED output S13 and what is different there, because the signals were exactly the same.
But in any case the camera needs for driving only an open collector, because normally there is 3.3V on the remote control pin. So for the right functioning (take pictures or turn on/off video) it is in AP enough to setup the relay output and add one Mosfet between pin S and camera input.
Runcam still did not reply on my e-mail question about this signal protocol, so “help yourself as you can”.