Pixhawk 4 mini FrSky Sbus port Problem

Hi to all…
I’m a newbie with ardupilot. I have bought a Pixhawk 4 Mini and load arducopter for use into my helirepo project… a class 130 CH-47 (about 1:40 scale)
I have spend a lot of night with a strange problem… i use a FrSky reciver with Sbus… i was unable to let it speek with the pixhawk… As all the docs tell i had connected the rx to the RC In port of px4 mini… No way it didn’t see any rc channel…
I i swich the rx to cppm mode and connect it to the PPM port, it works, but see only 8 channels.
The last try i make is to switch back to SBus mode but leave the rx connected to PPM port and not RC In… and wow… it works and see all the 16 sbus channel…
Is it normal?? and why the varius doc tell to connect the sbus to RC In if it dind’t work??


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What model FrSky receiver are you using?

Thanks for your reply.
I use a X4RSB and try also with a XH+. Same result… The pixhawk see all the 16 sbus channel only if connect to PPM port.

ArduPilot can take any supported protocol over a single input.
Put the receiver in sbus mode, and connect it to the ppm input. It will work just fine.
This frees the rc-in to be used as half a serial port (serial 5). More details here:

As for why the discrepancy: you’ll have to ask Holybro why the documentation is for PX4, when the majority of users prefer ArduPilot. I agree it’s confusing and frustrating.

Thanks James. I already made as you tell me… And work fine… But as newbie i ask if it’s correct :wink:

The strange is also with the PX4 firmware the problem is the same…
Maibe they have to correct the manual :slight_smile:

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