Using AUX Port on Radiomaster MT12 for S.BUS Trainer

[armin-rc]

Hello,

is the AUX port on the Radiomaster MT12 with MPM (4-in1) supposed to support Trainer via S.BUS? The corresponding setting in the menu is there (SYS > Hardware > Serial Port > AUX1 > SBUS Trainer) and in the model menu the setting is also set (MDL > SETUP > Trainer Mode > Master/SBUS). Of course I activated the trainer mode via a special function.

The whole setup is as follows:
The Rx (Radiolink R7FG) is connected via S.BUS to the AUX Port of the MT12. The blue LED on the Rx is constant on which indicates that it is running in S.BUS mode. A Radiomaster TX16S (which acts as the studend radio) is bound to that Rx. The MT12 is bound to another Rx in the model.

I red in a pull request on github that the UART in the MT12 cannot handle a "true" S.BUS signal (with "true" I mean as it was specified by Futaba [idle low / active high]) and that the signal has to be "inverted" (active low / idle high). I tried both signal variants and so far had no success. I checked the signals via an oscilloscope and a logic analyzer. They were looking good.

Does anybody know if it is supposed to work or am I hunting down a problem that cannot be resolved currently?

Link to the pull request:
#4668

Thanks,
Armin
arminRC