u/CorrectAir8833

I put together a small ROS 2 subsystem that turns a 2-DOF pan/tilt platform and a cheap 2D LiDAR into a stop-and-capture 3D scanner, and figured it might be useful to someone else here.

The setup: two Feetech STS3215 serial-bus servos aim an LDROBOT LD19. A node sweeps the platform and an assembler stacks the 2D scans into a `PointCloud2` using the live TF tree. There's an optional MQTT bridge so an external controller (in my case a microcontroller mission queue on a rover) can trigger scans and get a completion handshake back.

It's a *complete* project — it even includes a fix to the LiDAR driver (upstream `ldlidar_stl_ros2` won't build on recent GCC/glibc; the patched fork is linked below). It talks to the rover over a well-defined set of MQTT messages, but every command also has an equivalent ROS 2 topic, so if you want a pure ROS 2 setup you just don't launch the bridge. (Personally I love the MQTT side — it lets me drive the whole thing from a tablet.)

No vendor SDK — the Feetech STS/SMS half-duplex protocol is implemented directly over pyserial, including handling the URT-1 adapter's habit of echoing every TX byte back on the RX line (the kind of thing that eats an evening if you don't know it's coming). The assembler is driver-agnostic: it consumes standard `sensor_msgs/LaserScan` on `/scan`, so any conformant 2D LiDAR should work.

It's running on an RK3588 today and is built to go headless on a Pi 5.

This is the first piece I'm open-sourcing from a larger autonomous rover project, GPL-3.0. I'd genuinely welcome feedback — particularly from anyone who's done multi-LiDAR or TF-timing work, since the scan-to-TF synchronization was the fussiest part to get right. But it does work! Happy to answer questions about any of it.

• Project: https://github.com/aa2mz/pan\_tilt\_lidar
• Patched LiDAR driver: https://github.com/aa2mz/ldlidar\_stl\_ros2