Pixracer + FrSky D8R-XP: No receive Channels detected

Hi all,

I’m trying to get a pixracer to run with an FrSky D8R-XP receiver. No luck so far: qGroundControl in radio calibration reports “0 Channels detected. At least 5 are required”.

using a logicanalyzer as well as an CC3D flight controller I could confirm that the transmitter + receiver works as intended. I’m pretty sure it’s wired up to PX4 correctly as well. I now suspect CPPM parsing not to work. Form a quick look into the firmware (drivers/px4fmu/fmu.cpp), there seems some autodetection between cppm, sbus, and three others going on. But no way to set/force one of the protocols.

Is this a known problem - is there some setting that I did not see? I could not find anything relevant. Or is there a way to debug this specifically?

Thanks and best regards,


Can you post an image of your radio wiring?

Hi Philip, i need few info about the correct setup of my pixracer r15 with GPS u-Blox Neo-M8N Dual Compass LIS3MDL+ IST8310. On pixracer I’ve installed the px4 firmware 1.8.0. When im booting the fc i have always the green led blinking but when im arming the drone in poshold i have always a blue fix led even ive a good gps signal.
Its normal this behavior or i must set different params?