Unclear Parameter Settings for Hardware Synchronization in ROS2 Humble Driver

[Liu-Jinxin]

---

Required Info
Camera Model	D435i / D455
Firmware Version	5.15.1
Operating System & Version	Ubuntu22.04
Kernel Version (Linux Only)	(e.g. 5.4)
Platform	PC
Librealsense SDK Version	{2.55.1 }
Language	{C/C#/labview/opencv/pcl/python/unity }
Segment	{Robot/Smartphone/VR/AR/others }
ROS Distro	Humble
RealSense ROS Wrapper Version	4.55.1

Issue Description

I am working on a project involving hardware synchronization for multiple cameras using the ROS2 driver. Despite setting the following ROS2 driver parameters intended to manage synchronization, the cameras are not synchronizing as they should:

 configurable_parameters = [  {'name': 'inter_cam_sync_mode',          'default': '1', 'description': 'Intel camera sync mode'},
{'name': 'output_trigger_enabled',       'default': 'true', 'description': 'Enable output trigger'},]

I am unclear on whether these settings are appropriate or even applicable for the ROS2 Humble driver. Could someone clarify if these parameters are correct for achieving hardware synchronization in this environment, or guide me on how to configure the driver properly for this purpose?

Any help or pointers to relevant documentation would be greatly appreciated!

Thank you!

[MartyG-RealSense]

Hi @Liu-Jinxin The above command's inter_cam_sync_mode parameter is only enabling sync on the Master camera by setting the parameter to '1'. The other cameras need to be set as Slaves in order for them to sync with the master camera by setting inter_cam_sync_mode to '2' on each one.

A way to do this may be to open multiple terminal windows (one for each camera), each with its own launch for a particular camera, and launch with inter_cam_sync_mode = 1 on one of the launches to configure the Master camera and set it to 2 on each of the Slave camera launches.

[Liu-Jinxin]

Hi @MartyG-RealSense

Thanks for your help! In ROS 1, I was able to configure the hardware synchronization by setting the following parameters directly in the launch file:

/camera/stereo_module/inter_cam_sync_mode: 1
/camera/stereo_module/output_trigger_enabled: true

However, it seems that these parameters in the launch file are not being correctly picked up in the ROS 2 launch configuration, which might be causing the inability to trigger synchronization as expected.

 {'name': 'stereo_module.intel_cam_sync_mode',   'default': '1', 'description': 'Intel camera sync mode'},
 {'name': 'stereo_module.output trigger enabled','default': 'true', 'description': 'Enable output trigger'},

Could you please advise on the correct way to specify these settings in a ROS 2 environment, or if there are different parameters I should be using to achieve this?

[Liu-Jinxin]

I've managed to resolve the issue. It turns out the correct parameters for ROS 2 should indeed specify the module name. Here are the corrected settings that worked for achieving hardware synchronization:

{'name': 'depth_module.inter_cam_sync_mode', 'default': '1', 'description': 'Intel camera sync mode'},
{'name': 'depth_module.output_trigger_enabled', 'default': 'true', 'description': 'Enable output trigger'},

Thanks for your help.

[MartyG-RealSense]

You are very welcome. It's great to hear that you achieved a solution. Thanks very much for the update and sharing the details of your solution!