# Connecting an RC Receiver on Linux

This topic shows how to setup a PX4 Linux-based autopilot to connect and use a [supported RC receiver](https://px4.gitbook.io/px4-user-guide/getting_started/rc_transmitter_receiver) on any serial port.

For RC types other than S.Bus, you can just connect the receiver directly to the serial ports, or to USB via a USB to TTY serial cable (e.g. like PL2302 USB to Serial TTL converter).

:::note For an S.Bus receiver (or encoder - e.g. from Futaba, RadioLink, etc.) you will usually need to connect the receiver and device via a [signal inverter circuit](#signal_inverter_circuit), but otherwise the setup is the same. :::

Then [Start the PX4 RC Driver](#start_driver) on the device, as shown below.

## Starting the Driver

To start the RC driver on a particular UART (e.g. in this case `/dev/ttyS2`):

```
rc_input start -d /dev/ttyS2
```

For other driver usage information see: [rc\_input](https://px4.gitbook.io/px4-user-guide/modules_main/modules_driver#rc-input).

## Signal Inverter Circuit (S.Bus only)

S.Bus is an *inverted* UART communication signal.

While some serial ports/flight controllers can read an inverted UART signal, most require a signal inverter circuit between the receiver and serial port to un-invert the signal.

:::tip This circuit is also required to read S.Bus remote control signals through the serial port or USB-to-TTY serial converter. :::

This section shows how to create an appropriate circuit.

### Required Components

* 1x NPN transistor (e.g. NPN S9014 TO92)
* 1x 10K resistor
* 1x 1K resistor

:::note Any type/model of transistor can be used because the current drain is very low. :::

### Circuit Diagram/Connections

Connect the components as described below (and shown in the circuit diagram):

* S.Bus signal → 1K resistor → NPN transistor base
* NPN transistor emit → GND
* 3.3VCC → 10K resistor → NPN transistor collection → USB-to-TTY rxd
* 5.0VCC → S.Bus VCC
* GND → S.Bus GND

![Signal inverter circuit diagram](https://4155462212-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-LArEa7z2SPawfl3HpCD%2Fuploads%2Fgit-blob-1d2a6651e5dc89154c12ab6575c1212791b7da6e%2Fdriver_sbus_signal_inverter_circuit_diagram.png?alt=media)

The image below shows the connections on a breadboard.

![Signal inverter breadboard](https://4155462212-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-LArEa7z2SPawfl3HpCD%2Fuploads%2Fgit-blob-0df6b7def0f9cc6f2716b2e550bf483a9306b2aa%2Fdriver_sbus_signal_inverter_breadboard.png?alt=media)
