PX4 Setup

Note

PX4 is currently used for the real robot exclusively and is not part of the simulation. Skip this section if you are not preparing for the lab experiments. If in doubt ask your supervisor.

Building the Firmware

If PX4 is used in combination with the onboard computer, make sure the firmware running on the FCU was built with RTPS support.

A tested PX4-Version is the commit 45b390b0bf.

$ git clone https://github.com/PX4/PX4-Autopilot.git \
&& cd PX4-Autopilot \
&& git checkout 45b390b0bf \
&& git submodule update --init --recursive

For this version the RTPS support is not enabled by default for the fmu-v4 target (i.e. the PixRacer). One has to modify the file boards/px4/fmu-v4/default.px4board and add the line

CONFIG_MODULES_MICRODDS_CLIENT=y

Also modify the autostart-line in src/modules/microdds_client/module.yaml if you want to have a namespace prepended to the topic names

set XRCE_DDS_ARGS "-t serial -d ${SERIAL_DEV} -b p:${BAUD_PARAM} -n uuv00"

Also a good starting point for a minimal set of bridged topics defined in src/modules/microdds_client/dds_topics.yaml is

Listing 3 src/modules/microdds_client/dds_topics.yaml
 1publications:
 2
 3  - topic: /fmu/out/failsafe_flags
 4    type: px4_msgs::msg::FailsafeFlags
 5
 6  - topic: /fmu/out/sensor_combined
 7    type: px4_msgs::msg::SensorCombined
 8
 9  - topic: /fmu/out/timesync_status
10    type: px4_msgs::msg::TimesyncStatus
11
12  - topic: /fmu/out/vehicle_odometry
13    type: px4_msgs::msg::VehicleOdometry
14
15subscriptions:
16
17  - topic: /fmu/in/vehicle_visual_odometry
18    type: px4_msgs::msg::VehicleOdometry

Build the firmware

make px4_fmu-v4

Normally, the microdds_client is started automatically, and no further actions are required. Anyhow, to manually start the microdds_client, go to the nsh terminal and run

$ microdds_client start -t serial -d /dev/ttyS2 -b 921600 -n uuv00

Configure the Firmware

Attention

Make sure you disable the GPS completely by changing its control mode parameter. Otherwise the the vision will be taken as odometry data instead of absolute positions.

Set XRCE_DDS_0_CFG to TELEM2, i.e. 102. If you want to, you can change the baudrate of TELEM2 at SER_TEL2_BAUD. But the default of 921600 should be just fine.

Note

Make sure you disable all MAVLink interfaces on TELEM2.

Install px4_msgs

Hint

Building and rebuilding px4_msgs takes very long, especially on the Raspberry Pi. Therefore, it is recommended to have an underlying workspace for packages that we are not modifying regularly.

A commit that is tested to be working with the above-mentioned version of PX4 is 8a7f3da.

Clone it into the ROS workspace

$ git clone https://github.com/PX4/px4_msgs.git \
&& cd px4_msgs \
&& checkout 8a7f3da

Install Micro-XRCE-DDS-Agent

Clone and build the agent

$ cd ~/ros2_underlay/src \
&& git clone https://github.com/eProsima/Micro-XRCE-DDS-Agent.git \
&& build_underlay

Running the Micro-XRCE-DDS-Agent

Replace device and baudrate with the correct values.

$ MicroXRCEAgent serial --dev /dev/fcu_data -b 921600

If the setup is working, ros2 topic list should show the FMUs in and out topics.

/uuv00/fmu/in/obstacle_distance [px4_msgs/msg/ObstacleDistance]
/uuv00/fmu/in/offboard_control_mode [px4_msgs/msg/OffboardControlMode]
/uuv00/fmu/in/onboard_computer_status [px4_msgs/msg/OnboardComputerStatus]
/uuv00/fmu/in/sensor_optical_flow [px4_msgs/msg/SensorOpticalFlow]
/uuv00/fmu/in/telemetry_status [px4_msgs/msg/TelemetryStatus]
/uuv00/fmu/in/trajectory_setpoint [px4_msgs/msg/TrajectorySetpoint]
/uuv00/fmu/in/vehicle_attitude_setpoint [px4_msgs/msg/VehicleAttitudeSetpoint]
/uuv00/fmu/in/vehicle_command [px4_msgs/msg/VehicleCommand]
/uuv00/fmu/in/vehicle_mocap_odometry [px4_msgs/msg/VehicleOdometry]
/uuv00/fmu/in/vehicle_rates_setpoint [px4_msgs/msg/VehicleRatesSetpoint]
/uuv00/fmu/in/vehicle_trajectory_bezier [px4_msgs/msg/VehicleTrajectoryBezier]
/uuv00/fmu/in/vehicle_trajectory_waypoint [px4_msgs/msg/VehicleTrajectoryWaypoint]
/uuv00/fmu/in/vehicle_visual_odometry [px4_msgs/msg/VehicleOdometry]
/uuv00/fmu/out/failsafe_flags [px4_msgs/msg/FailsafeFlags]
/uuv00/fmu/out/sensor_combined [px4_msgs/msg/SensorCombined]
/uuv00/fmu/out/timesync_status [px4_msgs/msg/TimesyncStatus]
/uuv00/fmu/out/vehicle_attitude [px4_msgs/msg/VehicleAttitude]
/uuv00/fmu/out/vehicle_control_mode [px4_msgs/msg/VehicleControlMode]
/uuv00/fmu/out/vehicle_local_position [px4_msgs/msg/VehicleLocalPosition]
/uuv00/fmu/out/vehicle_odometry [px4_msgs/msg/VehicleOdometry]
/uuv00/fmu/out/vehicle_status [px4_msgs/msg/VehicleStatus]

Manual Connection to QGroundControl

First, the mavlink router needs to be running on the vehicle.

In QGC, click on the top left corner icon -> Application settings -> Comm links -> Add

../../_images/qgc_where_to_find_settings.png

Fig. 2 Where to find the settings.

Add a TCP comm link with standard settings. Add the vehicle’s name and IP address. It should look like this:

../../_images/qgc_manually_add_tcp_connection.png

Fig. 3 TCP comm link settings for UUV02.

Now, you should be able to connect. The vehicle setup page should open:

../../_images/qgc_vehicle_setup.png

Note

After this first manual connection via TCP from your ground control station to the vehicle, the UDP endpoint should/will start working.

Sensor Calibration

You might have to calibrate the vehicle’s sensors. Click on Sensors:

../../_images/qgc_sensors_setup.png

and follow the instructions.