Setup & Getting Started (PX4)

User Guide

Getting started

In this section of the manual, we will cover the basic setup of the units. To setup the RTK units with PX4, you will need QGroundControl installed on your computer or Ground Control Station and PX4 installed on your flight controller. If you are using Ardupilot firmware and Mission Planner ground station software, please refer the Ardupilot setup guide. Using RTK (Real Time Kinematics) greatly increases the accuracy of the GPS positioning. RTK mode requires a base station and a rover station. Either Rover or Helical can be use a rover station. The Helical or the "Base" model, we recommend using the "Base" model should be used as base station since it allows a larger external antenna.

More information can be found in PX4 Doc on RTK GPS

Preparation

To use the H-RTK on a drone, you need the following hardware:

• A flight controller with CAN port for the GPS, a free serial port for the radio telemetry. A Holybro Pixhawk 4 or newer is recommended. This example uses a Pixhawk 6C.

• A pair of radio telemetry radios for data transmission, this example uses Holybro Sik Telemetry Radio V3

• A H-RTK Rover or Helical (UAV side)

• A H-RTK Helical or Base Station H-RTK F9P (base station side)

• Ground Station (Ex: Tablet, Laptop, GCS, etc.)

Connection Diagram

Refer to these Setup Guide if you are using Multiple Aircraft.

Connect the devices as follow:

Before you start the setup, make sure both RTK units have a good view of the sky so they can receive the best signal from the satellites.

Flight controller Setting with PX4 Firmware

If you are using DroneCAN version, make sure The firmware used for flight control is PX4 V1.12.3 or higher, which automatically allocate 2 node ID for DroneCAN. Older firmware might not be able to automatically allocate 2 node ID. You will need to use newer firmware and perform following operation to manually assigning node ID. Connect the GPS to the flight controller.

If you are using DroneCAN version, connect the flight controller to QGC and Make sure the parameter UAVCAN_ENABLE has been set to "Sensor Automatic Config". The DroneCAN-F9P will now work.

RTK GPS settings

The RTK GPS settings are specified in the QGroundControl General Settings (opens new window) (Settings View > General Settings > RTK GPS).

These settings define the minimum duration and minimum accuracy for completing the RTK GPS setup process (known as "Survey-In").

TIP: You can save and reuse a base position to save time: perform Survey-In once, select Use Specified Base Position and press Save Current Base Position to copy in the values for the last survey. The values will then persist across QGC reboots until they are changed.

Flight Controller Setup

The UAVCAN_PUB_RTCM parameter needs to be set to Enabled.

MAVLink2

The MAVLink2 protocol must be used because it makes more efficient use of lower-bandwidth channels. This should be enabled by default on recent builds. Holybro SiK Telemetry Radio uses MAVLink2 protocol by default. But if you are not sure about the status of the data transmission, you can go through the following steps to ensure MAVLink2 is used:

Update the telemetry module firmware to the latest version

Set MAV_PROTO_VER to 2

Tuning

You may also need to tune some parameters of the flight controller as the default parameters are tuned assuming a GPS accuracy in the order of meters, not centimeters. For example, you can decrease EKF2_GPS_V_NOISE and EKF2_GPS_P_NOISE to 0.2.

RTK Connection Process

The RTK GPS connection is essentially plug and play:

1.) Start QGroundControl and attach the base RTK GPS via USB to the ground station. The device is recognized automatically.

2.) Start the vehicle and make sure it is connected to QGroundControl.

QGroundControl displays an RTK GPS status icon in the top icon bar while an RTK GPS device is connected (in addition to the normal GPS status icon). The icon is red while RTK is being set up, and then changes to white once RTK GPS is active. You can click the icon to see the current state and RTK accuracy.

3.) QGroundControl then starts the RTK setup process (known as "Survey-In").

Survey-In is a startup procedure to get an accurate position estimate of the base station. The process typically takes several minutes (it ends after reaching the minimum time and accuracy specified in the RTK settings).

You can track the progress by clicking the RTK GPS status icon.

Once Survey-in completes, the RTK GPS icon changes to white and QGroundControl starts to stream position data to the vehicle.

Vehicle GPS switches to RTK mode. The new mode is displayed in the normal GPS status icon.

Tip: The Orange RTK FIX led on F9P module will blink when receiving RTCM data. And the led will stay on when the Rover module has entered the RTK status.