Low voltages when trying to hardware sync multiple D455 cameras

[Nico-Sander]

Required Info
Camera Model	D455 }
Firmware Version	5.16.0.1
Operating System & Version	Ubuntu 20.04
Kernel Version (Linux Only)	5.10.192-tegra
Platform	NVIDIA Jetson Orin Dev Kit 64GB
SDK Version	2.55.1
Language	python
Segment	Robotics

---

Issue Description

Hi there, I am trying to set up Hardware Sync between 2 Intel RealSense D455 cameras. I am using Python to configure and start the cameras. According to the "Multi camera configurations" whitepaper (https://dev.intelrealsense.com/docs/multiple-depth-cameras-configuration) Pins 5 (Signal) and Pins 9 (Ground) of both cameras need to be connected. In the python file I then used the following code to set on of my cameras to "Master":

device_right.first_depth_sensor().set_option(rs.option.inter_cam_sync_mode, 1) # Master device_left.first_depth_sensor().set_option(rs.option.inter_cam_sync_mode, 2) # Slave

Here's the problem: When checking the signals sent between the two cameras on Pins 9 and 5, i get the correct frequency of about 30Hz (camera configured to 30fps), but the Peak-to-Peak Voltage is only about 100mV. From what I've read, a Peak-to-Peak Voltage of 1.8V is needed for the "slave"-camera to recognize the trigger signal. I have measured the Voltage directly at the Pins, so faulty connections are not the problem.

Has anyone experienced a similar issue before. I hope someone can help me with known explanations / solutions for my problem.

Thanks

[MartyG-RealSense]

Hi @Nico-Sander Are you measuring for 1.8 V on Pin 5 of the Master camera whilst the Master camera is active, please? A Master camera generates a sync pulse on Pin 5 (the sync pin) when its Inter Cam Sync Mode is set to 1. The camera would have to be actively depth-streaming in order for the trigger pulse to be generated.

[Nico-Sander]

Hello Marty, yes the Master camera is actively streaming. I am visualizing the depth and color output while measuring the sync signals. I like to add, that i get the same voltage readings when starting the camera with realsense-viewer. So the Inter Sync Mode seems to be set correctly.

[MartyG-RealSense]

The value of 1.8 v is always referred to in regard to use of an external trigger signal. It is never referred to in regard to triggering by a master camera.

A known characteristic of a trigger generated by a master camera is that it should have a pulse width of 50 microseconds, whilst an external trigger should have a pulse width of 100 microseconds or more.

[Nico-Sander]

Hi Marty, thanks for the explanation. I will try to measure the pulse width tomorrow and will get back to you.

[Nico-Sander]

Quick follow up on my issue. The problem is resolved and the sync seems to be working. I tried to measure the pulse-width today and was able to see the 50us pulse-width generated by the master camera.

You can also see that the voltage is now 1.74V, maybe a restart of my system was all that was necessary to get a better voltage.

I validated that the sync is working, by placing a millisecond clock in the overlapping field of view of the 2 cameras. Both cameras always show the exact same state of the clock, so the cameras capture the images within the same millisecond.

[MartyG-RealSense]

That's great news that your setup is working correctly. Thanks very much for the update!