Extra PWM channel

ArduCopter
1

Hi all,
In addition to the 4ESC I need to drive an additional servo motor using a PWM, using an Erle-Brain3. I tried to read the apm code, module by module from its source:

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I figured it must be in one of these files. Does anyone know which one and How to use it?
Thanks

2

Can you get away with using the mavlink DO_SET_SERVO command?

3

ServoN_function might be worth looking into