# PX4 Instructions

## Single GPS Configuration

Connect the ARK MOSAIC-X5 RTK GPS to the flight controller's CAN port using a standard 4-pin JST-GH cable.

### Flight Controller Parameters

Set the following in *QGroundControl* and reboot the flight controller.

#### Required

| 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    |
| [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

| 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 |
| [UAVCAN\_SUB\_IMU](https://docs.px4.io/main/en/advanced_config/parameter_reference.html#UAVCAN_SUB_IMU)                                                                                                                                                                                                                        | Set to `1` to subscribe to DroneCAN `RawIMU` 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) | GPS offset from the vehicle center of gravity (meters) |

### CAN Node Parameters

Set the following on the GPS and reboot the node. CAN node parameters can be configured using either:

* [QGroundControl](https://docs.px4.io/main/en/dronecan/#qgc-cannode-parameter-configuration) — each CAN node appears as a separate *Component X* entry under **Vehicle Settings > Parameters**.
* The [DroneCAN GUI Tool](/knowledge-base/knowledge-base/dronecan-gui-tool-guide.md).

#### Required

| Parameter         | Value | Description                                  |
| ----------------- | ----- | -------------------------------------------- |
| `CANNODE_PUB_MAG` | 1     | Publish magnetometer messages on the CAN bus |

#### Optional

| Parameter          | Description                                                                                                                                                                                   |
| ------------------ | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `CANNODE_TERM`     | Set to `1` if this is the last node on the CAN bus                                                                                                                                            |
| `CANNODE_PUB_BARO` | Set to `1` to publish barometer messages on the CAN bus                                                                                                                                       |
| `CANNODE_PUB_IMU`  | Set to `1` to publish `RawIMU` messages on the CAN bus.                                                                                                                                       |
| `SEP_OUT_RATE`     | Output rate for GNSS data messages: `-1` = OnChange, or `50` / `100` / `200` / `500` ms                                                                                                       |
| `SEP_PVT_MODE`     | Bitmask of allowed PVT modes for Rover operation. Bits: `1` = StandAlone, `2` = DGNSS, `4` = RTKFloat, `8` = RTKFixed. Default `15` (all). The receiver uses the most accurate mode available |
| `SEP_RCV_DYN`      | Receiver dynamics model: `0` = Static, `1` = Quasistatic, `2` = Pedestrian, `3` = Automotive, `4` = RaceCar, `5` = HeavyMachinery, `6` = UAV (default), `7` = Unlimited                       |

***

## Troubleshooting

* See our [GPS Placement](/knowledge-base/knowledge-base/gps-placement.md) guide for mounting best practices, interference sources, and antenna positioning.


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