FrSky RX4R Receiver and Matek F405 Wing

I have a question on setting up FrSky RX4R with Matek F405 Wing. Initially I had some trouble getting the Rx to talk to the Matek board, but I managed to get it working by plugging in the Sbus out from the Rx to the R2 pin on the Matek board. I discovered this by mistake, actually, and it’s very odd since it simply won’t work with the Rx Sbus out connected to the Sbus pin on the Matek board. Any thoughts on why this might be?

Not sure if I’m happy to fly like this, and I occasionally get “No RC Receiver” error warning in Mission Planner.

Any thoughts on why the Rx won’t work when connected to the Sbus port on the Matek board?


according to the f405 diagram sbus and r2 are the same pins apart from sbus as inverter built in.
if your receiver works on one and not the other i would assume the receiver doesn’t need to be inverted!
how close is your transmitter to the receiver when you get the “No RC Receiver” message. frsky like to be a few meters away from each other.

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Thanks Dale, that makes sense now. I actually saw “IBUS” mentioned for RX2 pad on the diagram on Matek website, so presumably that’s for “Inverted”.

Regarding radio dropout, yes, I think it was a case of being to close (it was less than a meter). Will do some more checks today with a few metres between Tx and Rx.

Thanks for your help.

@dale589 another question if I may…what should the protocol setting be for the serial port/R2 pad? As I mentioned, RC is working happily, and this is on Mavlink (option 1 in Mission Planner) but surely it should be something else? I have tried -1 for “None” and that also works, so maybe just stick with that? Other options are as follows:
-1:None 1:MAVLink1 2:MAVLink2 3:Frsky D 4:Frsky SPort 5:GPS 7:Alexmos Gimbal Serial 8:SToRM32 Gimbal Serial 9:Rangefinder 10:FrSky SPort Passthrough (OpenTX) 11:Lidar360 13:Beacon 14:Volz servo out 15:SBus servo out 16:ESC Telemetry 17:Devo Telemetry

Lost me when you started talking about mavlink. but would seem logical to use none as all the other options have nothing to do with a rx4r receiver