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GMSL Link Margin Testing

Overview​

GMSL Link Margin Testing validates the link margin, which is the difference between signal strength and receiver sensitivity. TechNexion VLS-GM2 cameras utilize the GMSL2 interface to transmit video data to the deserializer.

We provide a fast and convenient way to perform validation using Docker containers. This approach ensures host stability while simplifying updates and maintenance.

System Requirements​

  • Platform: NVIDIA Jetson Orin Nano Development Kit
  • JetPack: 6.2.1 (L4T r36.4.4)
  • Software: Docker Engine
important

Users must first install the driver. Refer to the VLS-GM2 installation guide: TechNexion Camera Modules for Orin Nano JetPack 6.x

Usage Steps​

1. Pull the Image​

sudo docker pull technexion/gmsl-linkmargin-tool:nv_jetson_36.4

2. Run the Container​

sudo docker run -d \
  --name gmsl-webui \
  --restart unless-stopped \
  --privileged \
  -p 8000:8000 \
  -e PYTHONUNBUFFERED=1 \
  technexion/gmsl-linkmargin-tool:nv_jetson_36.4

3. Access the Web UI​

After startup, open your browser and navigate to:

http://<jetson-ip>:8000

Query Jetson IP: hostname -I | awk '{print $1}'

4. Configure and Run the Test​

  1. Select I2C Bus: Choose the I2C bus you want to test.
  2. Select Link: Choose the link you want to test, it will auto-detect the link when the i2c bus is selected.
  3. Select Algorithm: Select the appropriate algorithm, default is Both Algorithms.
  4. Click Start: The tool will automatically start the link margin test.

Test Result Sample​

Test Result Sample

5. Stop the Container​

sudo docker stop gmsl-webui

6. Remove the Container (Optional)​

sudo docker rm gmsl-webui

I2C Bus Check​

Before selecting the I2C Bus in the Web UI after startup, you can first check the available buses on the Jetson:

i2cdetect -l

Common GMSL2 connected buses (varies by board):

BusController
i2c-9i2c-2-mux (chan_id 0)
i2c-10i2c-2-mux (chan_id 1)

Then check if the devices exist, for example:

$ sudo i2cdetect -r -y <bus_number>

The actual address of SerDes devices are depended on the device tree. You can check the device tree to find the actual address.

Troubleshooting​

IssueSolution
Web UI fails to openEnsure container is running: sudo docker ps
GMSL device undetectedVerify I2C Bus selection; check Web UI detection log after switching Bus
Container fails to startCheck container logs: sudo docker logs gmsl-webui
I2C permission errorMake sure the --privileged parameter was included when starting
iptables error causing startup failureSee explanation below

Startup Failure due to Missing iptables Module​

Error Message:

docker: Error response from daemon: failed to set up container networking: failed to
create endpoint gmsl-webui on network bridge: Unable to enable DIRECT ACCESS
FILTERING - DROP rule: (iptables failed: iptables --wait -t raw -A PREROUTING -d
172.17.0.2 ! -i docker0 -j DROP: iptables v1.8.7 (legacy): can't initialize iptables
table `raw`: Table does not exist (do you need to insmod?)
Perhaps iptables or your kernel needs to be upgraded.
(exit status 3))

Cause: Custom kernels (such as RT kernels or minimal kernels) might not load the iptables raw table module, leading to Docker bridge networking failing to create packet filtering rules.

Solution: Use --net=host to Bypass iptables

--net=host allows the container to directly share the host's networking interfaces, bypassing the need for iptables/NAT, and directly binding port 8000 on the host:

sudo docker run -d \
  --name gmsl-webui \
  --restart unless-stopped \
  --privileged \
  --net=host \
  -e PYTHONUNBUFFERED=1 \
  technexion/gmsl-linkmargin-tool:nv_jetson_36.4

Note: When using --net=host, port mapping -p 8000:8000 is not needed as it is invalid in the host networking mode.

After starting, access directly via the Jetson IP with port 8000:

http://<jetson-ip>:8000