# PX4 Instructions

Find most up to date documentation at <https://docs.px4.io/main/en/dronecan/ark_gps.html>

### Hardware Setup <a href="#hardware-setup" id="hardware-setup"></a>

#### Wiring <a href="#wiring" id="wiring"></a>

The ARK GPS is connected to the CAN bus using a Pixhawk standard 4 pin JST GH cable. For more information, refer to the [CAN Wiring](https://docs.px4.io/main/en/can/#wiring) instructions.

#### Mounting <a href="#mounting" id="mounting"></a>

The recommended mounting orientation is with the connectors on the board pointing towards the **back of vehicle**.

The sensor can be mounted anywhere on the frame, but you will need to specify its position, relative to vehicle center of gravity, during [PX4 configuration](https://docs.px4.io/main/en/dronecan/ark_gps.html#px4-configuration).

### Firmware Setup <a href="#firmware-setup" id="firmware-setup"></a>

ARK GPS runs the [PX4 DroneCAN Firmware](https://docs.px4.io/main/en/dronecan/px4_cannode_fw.html). As such, it supports firmware update over the CAN bus and [dynamic node allocation](https://docs.px4.io/main/en/dronecan/#node-id-allocation).

ARK GPS boards ship with recent firmware pre-installed, but if you want to build and flash the latest firmware yourself see [PX4 DroneCAN Firmware > Building the Firmware](https://docs.px4.io/main/en/dronecan/px4_cannode_fw.html#building-the-firmware).

* Firmware target: `ark_can-gps_default`
* Bootloader target: `ark_can-gps_canbootloader`

### PX4 Configuration <a href="#px4-configuration" id="px4-configuration"></a>

{% hint style="warning" %}
The ARK GPS will not boot if there is no SD card in the flight controller when powered on.
{% endhint %}

Connect the ARK GPS CAN to the Pixhawk CAN. Once parameters are set the module will be detected on boot and GPS data should arrive at 10Hz. See [DroneCAN > Enabling DroneCAN](https://docs.px4.io/main/en/dronecan/#enabling-dronecan) for more detail.

#### Required Parameters

Set the following in *QGroundControl* and reboot the autopilot:

| Parameter                                                                                               | Value | Description                                                                          |
| ------------------------------------------------------------------------------------------------------- | ----- | ------------------------------------------------------------------------------------ |
| [UAVCAN\_ENABLE](https://docs.px4.io/main/en/advanced_config/parameter_reference.html#UAVCAN_ENABLE)    | 2     | Enable DroneCAN with dynamic node allocation (use `3` if also driving DroneCAN ESCs) |
| [UAVCAN\_SUB\_GPS](https://docs.px4.io/main/en/advanced_config/parameter_reference.html#UAVCAN_SUB_GPS) | 1     | Subscribe to DroneCAN GPS messages                                                   |
| [UAVCAN\_SUB\_MAG](https://docs.px4.io/main/en/advanced_config/parameter_reference.html#UAVCAN_SUB_MAG) | 1     | Subscribe to DroneCAN magnetometer messages                                          |
| [EKF2\_GPS\_CTRL](https://docs.px4.io/main/en/advanced_config/parameter_reference.html#EKF2_GPS_CTRL)   | 7     | Enable GPS fusion (lon/lat + alt + 3D velocity)                                      |

#### Optional Parameters

| Parameter                                                                                                                                                                                                                                                                                                                      | Description                                                                                                                                                      |
| ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | ---------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| [UAVCAN\_SUB\_BARO](https://docs.px4.io/main/en/advanced_config/parameter_reference.html#UAVCAN_SUB_BARO)                                                                                                                                                                                                                      | Set to `1` to subscribe to DroneCAN barometer messages                                                                                                           |
| [EKF2\_GPS\_POS\_X](https://docs.px4.io/main/en/advanced_config/parameter_reference.html#EKF2_GPS_POS_X) / [EKF2\_GPS\_POS\_Y](https://docs.px4.io/main/en/advanced_config/parameter_reference.html#EKF2_GPS_POS_Y) / [EKF2\_GPS\_POS\_Z](https://docs.px4.io/main/en/advanced_config/parameter_reference.html#EKF2_GPS_POS_Z) | ARK GPS offset from the vehicle center of gravity (meters)                                                                                                       |
| [CANNODE\_TERM](https://docs.px4.io/main/en/advanced_config/parameter_reference.html#CANNODE_TERM)                                                                                                                                                                                                                             | Set to `1` on the ARK GPS via the [DroneCAN GUI Tool](/knowledge-base/knowledge-base/dronecan-gui-tool-guide.md) if this is the last node on the CAN bus         |
| [CANNODE\_PUB\_IMU](https://docs.px4.io/main/en/advanced_config/parameter_reference.html#CANNODE_PUB_IMU)                                                                                                                                                                                                                      | Set to `1` on the ARK GPS via the [DroneCAN GUI Tool](/knowledge-base/knowledge-base/dronecan-gui-tool-guide.md) to publish the `RawIMU` messages on the CAN bus |
| [UAVCAN\_SUB\_IMU](https://docs.px4.io/main/en/advanced_config/parameter_reference.html#UAVCAN_SUB_IMU)                                                                                                                                                                                                                        | Set to `1` on the autopilot to subscribe to DroneCAN `RawIMU` messages. Requires `CANNODE_PUB_IMU` to also be set on the ARK GPS                                 |


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