# 使用机载计算机与 Pixhawk 控制器

PX4 running on Pixhawk-series flight controllers can connect to a companion computer using any free configurable serial port, including the Ethernet port (if supported).

See [Companion Computers](../companion_computer/index.md) for information about supported hardware and general setup.

## 机载计算机软件

机载计算机需要运行能与飞控通信的软件，并将消息路由到地面站和云端。

Common options are listed in [Companion Computers > Companion Computer Setup](../companion_computer/index.md#companion-computer-software).

## 以太网设置

以太网是推荐的连接方式，如果飞行控制器支持的话。
See [Ethernet Setup](../advanced_config/ethernet_setup.md) for instructions.

## Serial Port Setup

These instructions explain how to setup the connection if you're not using Ethernet.

### Pixhawk Configuration

PX4 expects companion computers to connect via `TELEM2` for offboard control.
The port is configured by default to interface using MAVLink.

If using MAVLink, no other PX4-side configuration should be required.
To use MAVLink on another port, and/or disable it on `TELEM2`, see [MAVLink Peripherals (GCS/OSD/Companion)](../peripherals/mavlink_peripherals.md) and [Serial Port Configuration](../peripherals/serial_configuration.md).

To use [ROS 2/uXRCE-DDS](../ros2/user_guide.md) instead of MAVLink on `TELEM2`, disable MAVLink on the port and then enable the uXRCE-DDS client on `TELEM2`(see [uXRCE-DDS > Starting the client](../middleware/uxrce_dds.md#starting-the-client)).

### Serial Port Hardware Setup

If you're connecting using a serial port, wire the port according to the instructions below.
All Pixhawk serial ports operate at 3.3V and are 5V level compatible.

:::warning
Many modern companion computers only support 1.8V levels on their hardware UART and can be damaged by 3.3V levels.
Use a level shifter.
In most cases the accessible hardware serial ports already have some function (modem or console) associated with them and need to be _reconfigured in Linux_ before they can be used.
:::

A safe and easy to set up option is to use an FTDI Chip USB-to-serial adapter board to connect from `TELEM2` on the Pixhawk to the USB port on the companion computer.
The `TELEM2` to FTDI wiring map is shown below.

| TELEM2 |                              | FTDI | &nbsp;       |
| ------ | ---------------------------- | ---- | -------------------------------- |
| 1      | + 5v (红色) |      | DO NOT CONNECT!                  |
| 2      | 2                            | 5    | 5                                |
| 3      | 3                            | 4    | 4                                |
| 4      | CTS（输入）                      | 6    | 6                                |
| 5      | RTS（输出）                      | 2    | 2                                |
| 6      | GND                          | 1    | FTDI GND (黑色) |

You may also be able to directly connect `TELEM2` directly to a companion computer serial port.
This is demonstrated for the Raspberry Pi in [Raspberry Pi Companion with Pixhawk](../companion_computer/pixhawk_rpi.md).

### USB Serial Port Software setup on Linux

On Linux the default name of a USB FTDI would be like `\dev\ttyUSB0`.
If you have a second FTDI linked on the USB or an Arduino, it will registered as `\dev\ttyUSB1`.
To avoid the confusion between the first plugged and the second plugged, we recommend you to create a symlink from `ttyUSBx` to a friendly name, depending on the Vendor and Product ID of the USB device.

Using `lsusb` we can get the vendor and product IDs.

```sh
$lsusb
    总线006 设备002：ID 0BDA:8153 Realtek 半导体公司
    Bus 006 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
    Bus 005 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
    Bus 004 Device 002: ID 05e3:0616 Genesys Logic, Inc.
    Bus 004 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
    Bus 003 Device 004: ID 2341:0042 Arduino SA Mega 2560 R3 (CDC ACM)
    Bus 003 Device 005: ID 26ac:0011
    Bus 003 Device 002: ID 05e3:0610 Genesys Logic, Inc. 4-port hub
    Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
    Bus 002 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
    Bus 001 Device 002: ID 0bda:8176 Realtek Semiconductor Corp. RTL8188CUS 802.11n WLAN Adapter
    Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
```

The Arduino is `Bus 003 Device 004: ID 2341:0042 Arduino SA Mega 2560 R3 (CDC ACM)`

The Pixhawk is `Bus 003 Device 005: ID 26ac:0011`

:::info
If you do not find your device, unplug it, execute `lsusb`, plug it, execute `lsusb` again and see the added device.
:::

Therefore, we can create a new UDEV rule in a file called `/etc/udev/rules.d/99-pixhawk.rules` with the following content, changing the idVendor and idProduct to yours.

```sh
SUBSYSTEM=="tty", ATTRS{idVendor}=="2341", ATTRS{idProduct}=="0042", SYMLINK+="ttyArduino"
    SUBSYSTEM=="tty", ATTRS{idVendor}=="26ac", ATTRS{idProduct}=="0011", SYMLINK+="ttyPixhawk"
```

Finally, after a **reboot** you can be sure to know which device is what and put `/dev/ttyPixhawk` instead of `/dev/ttyUSB0` in your scripts.

:::info
Be sure to add yourself in the `tty` and `dialout` groups via `usermod` to avoid to have to execute scripts as root.
:::

```sh
usermod -a -G tty ros-user
    usermod -a -G dialout ros-user
```
