I tried transmitter tuning on arducopter 4.5.5 as well as with 4.5.6.
I get always the message „Invalid channel option (219)“. I tried it with different tuning parameters, always error message. Installing 4.6dev it works flawless without any error message.
FC: Holybro Pixhawk 6c mini
got the same problem with ArduCopter 4.5.7 and a Holybro Durandal. Did you find a solution?
edit: it seems to come first with 4.6 →
“RC based tuning (aka CH6 tuning) can use any RC aux function channel (see RCx_OPTION = 219)”
But its strange since I used RC tuning with older firmwares before…
Also getting this issue on a matek h743 v3 wing running v4.5.7- transmitter tuning set to rc6 a described on wiki. Rolled firmware back to v4.5.4 and still getting the issue.