Hello. I use FrSky receiver. For big gliders I need 24 channels. Surprisingly Ardupilot works with 24 channel SBUS input (of course without reading channels 17-24), I use channels 17-24 with RB 30 / RB40 for servos output. I have noticed strange thing, when I use channel 17 and put it somewhere below -50% (it means -100 - -50%) then it triggers failsafe and Ardupilot stops reading receiver channels. When I fix channel 17 to 0%, then I can use any channels 1-16, 18-24 without problem. I believe this is bug from SBUS protocol interpretation…
24 Channels is FrSky’s own extension of the SBUS protocol. The functionality can only be used in the FrSky universe …