PX4 1.15.4 - XRCE-DDS over USB

PX4 Autopilot
1

I am currently using PX4 v1.15.4 on a Pixhawk 2.4.8 (also testing with Cube Orange), and I am trying to establish communication with ROS 2 using Micro XRCE-DDS.

Normally, we are able to successfully connect using the TELEM2 port with a custom cable (TX, RX, GND) from the autopilot to the Raspberry Pi 4. However, in our current setup, TELEM1 and TELEM2 are already occupied for other peripherals.

So, we attempted to create a custom USB cable by connecting only TX, RX, and GND lines from the autopilot’s micro-USB port to the Raspberry Pi. We intentionally disabled the 5V line to avoid any power conflict, as both devices are externally powered.

However, after plugging in the USB, no /dev/ttyACM* device appears on the Raspberry Pi, and the Micro XRCE Agent does not detect any connection.

I suspect that PX4 might not support XRCE over USB CDC directly, or that this port is limited to MAVLink only.

My questions are:

  1. Is it possible to use the micro-USB port for XRCE-DDS communication if only TX/RX/GND are wired (no VCC)?
  2. If not, since TELEM1 and TELEM2 are already in use, what would be the best alternative UART port to use for XRCE communication ?
  • For example, can I repurpose TELEM3, SERIAL4/5, or GPS2 reliably for XRCE-DDS?
  1. Any known issues or limitations for XRCE-DDS over USB on Cube Orange or Pixhawk 2.4.8?
    Thank you!