# 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](https://headtracker.gitbook.io/head-tracker-v2.2/getting-started/wiring/option-2-wired/serial-bus-sbus/radio-master-tx16s-setup "mention"). The new wiring connecting it to Aux2 for SBUS mode is shown below.

### Wiring

{% hint style="danger" %}
Note that Arduino TX is connected to TX on the J2(AUX2) Connector. The Radio Master Mainboard has incorrectly labeled RX and TX pins.
{% endhint %}

{% hint style="warning" %}
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.
{% endhint %}

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