# Connecting Raspberry Pi to the flight controller

In order to program [autonomous flights](simple_offboard.md), [work with Pixhawk or Pixracer over Wi-Fi](gcs_bridge.md), use [controller app](rc.md) and access other functions you need to connect your Raspberry Pi to the flight controller.

## USB connection

USB connection is the preferred way to connect to the flight controller.

<img src="../assets/assembling_clever4/usb_connection_1.png" alt="USB connection" height=400 class="zoom border center">

1. Connect your FCU to the Raspberry Pi using a microUSB to USB cable.
2. [Connect to the Raspberry Pi over SSH](ssh.md).
3. Make sure that the connection is working properly by [running the following command on the Raspberry Pi](cli.md):

    ```bash
    rostopic echo /mavros/state
    ```

    The `connected` field should have the `True` value.

> **Hint** You need to set the `CBRK_USB_CHK` [parameter](parameters.md) to 197848 for the USB connection to work.

## UART connection

UART connection is another way for the Raspberry Pi and FCU to communicate.

<img src="../assets/raspberry-uart-telemetry2.png" alt="UART connection via TELEM2" height=400 class="zoom border center">

If the pin marked GND is occupied, you can use any other ground pin (look at the [pinout](https://pinout.xyz) for reference).

1. Connect the TELEM 2 port on the flight controller using a UART cable to the Raspberry Pi pins following this instruction: the black cable (*GND*) to Ground, the green cable (*UART_RX*) to *GPIO14*, the yellow cable (*UART_TX*) to *GPIO15*. Do not connect the red cable (*5V*).
2. In PX4 of version v1.9.0 or higher, set parameter values: `MAV_1_CONFIG` to TELEM 2, `SER_TEL2_BAUND` to 921600 8N1. In PX4 of version [prior to v1.9.0](https://github.com/mavlink/qgroundcontrol/issues/6905#issuecomment-464549610) the parameter `SYS_COMPANION` should be set to `Companion Link (921600 baud, 8N1)`, to set it correctly use the old version of QGC [v3.3.1](https://github.com/mavlink/qgroundcontrol/releases/tag/v3.3.1).
3. [Connect to the Raspberry Pi over SSH](ssh.md).
4. Check the presence of the parameters `enable_uart=1` and `dtoverlay=pi 3-disable-bt` in the file `/boot/config.txt` by [running the following command on the Raspberry Pi](cli.md):

    ```bash
    cat /boot/config.txt | grep -E "^enable_uart=.|^dtoverlay=pi3-disable-bt"
    ```

    If the parameters in the file are different or missing, then edit the file and restart the Raspberry Pi.

5. Change the connection type from `usb` to `uart` in the Clover' launch file `~/catkin_ws/src/clover/clover/launch/clover.launch`:

    ```xml
    <arg name="fcu_conn" default="uart"/>
    ```

    If you change the launch file, you need to restart the `clover' service:

    ```bash
    sudo systemctl restart clover
    ```

6. Make sure that the connection is working properly by running the following command:

    ```bash
    rostopic echo -n1 /mavros/state
    ```

    The `connected` field should have the `True` value.

Read more in the PX4 docs: https://docs.px4.io/main/en/peripherals/serial_configuration.html.

**Next**: [Using QGroundControl over Wi-Fi](gcs_bridge.md)