Remapping option for channel 5 in SBUS

[Kjblootens]

Discussed in #2479

^{Originally posted by apiening November 19, 2023}
I have an airplane from FMS which has a stabilizer system (Reflex V2) which accepts SBUS. I enabled SBUS output for my RX (ELRS 3.3) and the control link works fine.
However, this stabilizer uses channel 5 with a three position mode switch to select between stabilizing modes (auto level, optimized, off). So when I configure it this way, I also disarm when I choose auto level stabilized mode.

I can assign the PWM outputs freely with ELRS, but is there a chance to remap channel 5 for the SBUS output?

[stevewitwitty]

I use SBUS with a Helicopter with the same issue. Helicopter uses channel 5 for stabilization mode. I got around this issue by going into the Express LRS lua script and changing the packet rate to 333Hz and then changing the switch mode to 16ch Rate/2. This then allows full resolution on channel 5 and the helicopter's stabilization mode switches on and off via a switch as needed. You can read further info here: https://www.expresslrs.org/software/switch-config/?h=switch

[stevewitwitty]

Forgot to say, there is a video which i found that helped me with this:

https://www.youtube.com/live/ARCfafma1rM?si=6MxiHAZJrRpC9g_N

Credit to RC Video Reviews for the video

[CapnBry]

A better solution is to allow remapping of all channels on the receiver. Not just SBUS not just CH5. This would let the user decide not only where CH5 ends up coming out, but also how the other channels are shifted.

[Kjblootens]

CapnBry. Yes that's implied here but still a good call out.

The problem only really exists for CH5 though. For any other issues there are very viable workarounds in terms of channel remapping on the TX.

The only viable workaround here are 16/2 Full modes where CH5 is not a prioritized channel along with CH1-4 as ALL packets get deprioritized (as per the switch config page, 16/2 modes have no lines bolded.) https://www.expresslrs.org/software/switch-config/

The ask is to enable serial output remapping (any serial protocol) so we can avail of the benefits of other switch modes while maintaining use of CH5 for e.g. flight mode switching where the target system (stabilizer) cannot be modified.

[CapnBry]

Yeah that's what I was saying, remap all channels to any order in the webui like you can do for pwm outputs.

I don't think we'll ever "deprioritize CH5" because it is how thousands of people have their stuff set up currently, and regular modes still only have space for a 1bit extra channel, but remapping the channels means that it doesn't matter because you can have the output CH5 be whatever, and 16ch mode (which kinda sucks) won't be as used. I think the major reason people use 16 channels at half rate is just for CH5.