Report how can I use the channels 15th and 16th in DIY Posted October 11, 2019 6 hours ago, erfan said: So you mean when a flight controller wants to control a function (rectractable landing gear) Then a servo*_function needs to be mapped ,right? Let's take a step back and continue to use the retractable landing gear as an example as I've had experience in setting that up. Firstly you have to of course know what is type of signal is required by the landing gear hardware for it to deploy and retract. In my case the landing gear controller required a PWM signal. Originally I did not have this driven from the flight controller but simply use one of the spare PWM outputs of the receiver which was in turn mapped to a switch on my transmitter. This worked but what would have happened if my drone lost the transmitter signal and the failsafe action was RTL or land ?. If the landing gear was retracted when this occurred there is no way to deploy it before it landed unless I could regain control over the drone. So this is the case when you want the flight controller to drive the PWM to the landing gear controller as the ArdCopter code does deploy it before it lands. Of course you also want to retract and deploy it from a switch on the transmitter. I used the first aux pins and so SERVO9_FUNCTION was set to landing gear and also CHXX_OPT was set to landing gear where XX was the sbus channel I was using from the receiver.