MicroXRCEAgent isn't transmitting ROS2 topics

PX4 Autopilot
1

Hello everyone!
I want to connect PX4 with a Raspberry to get ROS2 topics, to do so, i’ve followed all the instructions of the documentation : Raspberry Pi Companion with Pixhawk | PX4 Guide (v1.17)

My issue is that the MicroXRCEAgent isn’t transmitting ROS2 topics from PX4 to ROS2 on the raspberry.

I receive some data on the UART serial port of the raspberry because if I change the PX4 parameters :

  • MAV_0_CONFIG=TELEM2
  • SER_TEL2_BAUD=921600 8N1
  • UXRCE_DDS_CFG=Disabled

to get the mavlink telemetry, I can receive data :

(python3-venv) root@raspberry:~# mavproxy.py --master=/dev/ttyAMA0 --baudrate 921600
Connect /dev/ttyAMA0 source_system=255
Log Directory: 
Telemetry log: mav.tlog
Waiting for heartbeat from /dev/ttyAMA0
MAV> Detected vehicle 1:1 on link 0
online system 1
POSCTL> Mode POSCTL
fence breach

(It also prove that my RX/TX cables are not inverted and the Raspberry Pi 5 is configured well)

In order to setup the uxrce_dds_client on PX4, I’ve set those parameters :

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Then I’ve disconnected the power supply of the Pixhawk, which is a USB-C cable connected to my PC, and started the MicroXRCEAgent :

drone@raspberry:~$ MicroXRCEAgent serial --dev /dev/ttyAMA0 -b 921600 -v6
[1783957839.318658] info     | TermiosAgentLinux.cpp | init                     | running...             | fd: 3
[1783957839.319064] info     | Root.cpp           | set_verbose_level        | logger setup           | verbose_level: 6

After reconnecting the power supply of the Pixhawk, nothing moves on the MicroXRCEAgent logs.

And, the PX4 console shows that the uxrce_dds_client is Running but disconnected

nsh> uxrce_dds_client status
INFO [uxrce_dds_client] Running, disconnected
INFO [uxrce_dds_client] Using transport: serial
INFO [uxrce_dds_client] timesync converged: false
uxrce_dds_client: cycle: 0 events, 0us elapsed, 0.00us avg, min 0us max 0us 0.000us rms
uxrce_dds_client: cycle interval: 0 events, 0.00us avg, min 0us max 0us 0.000us rms

Also, the PX4 topics doesn’t appear on ROS2 :

drone@raspberry:~$ ros2 topic list
/parameter_events
/rosout

Here is my components versions :

  • Pixhawk 6c
  • PX4 v1.17 (flashed with QGroundControl)
  • Raspberry Pi 5 (Ubuntu 24.04)
  • MicroXRCEAgent v2.4.3 (build standalone, i’ve also tried the ROS2 build with ROS2 Jazzy)
  • ROS2 (I’ve tried Jazzy and and Humble version)

Thanks for your help!

2

Have you built the px4_msgs ROS package and sourced its workspace in your terminal?

I recently got my setup to work (although I was using an FTDI connector) and the details are as follows:

  1. PX4 Autopilot firmware: 1.16
  2. px4_msgs branch: release/1.16
  3. xrce agent baud rate: 921600

I would also recommend trying the baud rate 115200, although I feel that should not be the issue.

Also I have a telemetry module on my TELEM1 port, so my MAV_0_CONFIG is set to TELEM1. I have my FTDI connector connected to TELEM2 port and hence my MAV_1_CONFIG is disabled and UXRCE_DDS_CFG is set to 102 (i.e. TELEM2)

3

Yep the px4_msgs ROS package was built and my workspace sourced before launching the ros2 topic list command.

I’ve also tried with the baud rate : 115200 but nothing is changing.

Can you precise exactly what version you used for PX4 :

  • release/1.16
  • v1.16.2
  • v1.16.1
  • v1.16.0

I’ve tested release/1.16 but it doesn’t work.

4

My PX4 Autopilot firmware version is 1.16.0

5

I’ve got the same issues with the 1.16.0 version of PX4

6

Are you using an FTDI (Pixhawk TELEM to Raspi USB connector) or using the UART port (Pixhawk TELEM to Raspi UART connector)?

7

I’m using the UART port of the raspberry and the TELEM2 port of the Pixhawk but I don’t have any FTDI connector close to me.
(I’ve already tested my TELEM to UART cable with a multimeter)

8

I found the issue :tada: , I tested the TX pin on the raspberry in doing a TX/RX loop because I was receiving data but not transmitting any of it, so the MicroXRCEAgent was not able to respond to the uxrce_dds_client on the Pixhawk.
The result of this is that the TX (GPIO14) pin isn’t working :skull:.

The solution :
I plugged my cables to another UART interface (UART1 : GPIO0/1) and it finally resolved the problem.

(I should’ve done this before :melting_face: )

9

Yay! I am glad you resolved the issue! :clap: