Radio Master TX16S Mk2

You can internally connect the second receiver Arduino inside the case of a Mk2 radio using the new 4 pin MX1.25 connector. The setup in the GUI and on the Radio are the same as the MK1. See, Radio Master TX16S Setup. The new wiring connecting it to Aux2 for SBUS mode is shown below.

Wiring

Note that Arduino TX is connected to TX on the J2(AUX2) Connector. The Radio Master Mainboard has incorrectly labeled RX and TX pins.

If you want to use this connector for SBUS you do Not want the Bluetooth option compiled into the radio firmware. You won't be able to pick the SBUS Trainer (Aux2) feature on that port. You will need to set AUX2 SBUS trainer under the Radio Hardware page.