How many USB 3.0 root hubs (i.e. host controllers) on Jetson TX2?

I’ve read the OEM design guide and some topics in this forum, and I understand a TX2 module has three USB 3.0 “ports”, USB_SS#0, USB_SS#1, USB_SS#2.
But I was not able to find the direct answer to my question - how many USB 3.0 root hubs on the module.

Do these three USB 3.0 ports share the 5Gbps bandwidth, or are they three independent root hubs?

I’d like to connect several high res USB 3.0 cameras and I’d like to now how many cameras I can connect to one TX2 at maximum.

Thank you very much in advance.


Total usb endpoints <= 70 is the limitation of device number. If you are using camera, then bandwidth maybe an issue but it does not have a concrete answer to you at this moment.

Thank you for the prompt reply.

The number of devices would never exceed 70.

“Several cameras” meant here is just 1 to 3 range.
Each camera requires full USB 3.0 bandwidth, so if the USB_SS#0, #1 and #2 share the bandwidth, only one camera can be connected.
If they are independent USB 3.0 root hubs and have full 5Gbps bandwidth, I can use three cameras with one TX2.
That is the point.

I’ve never checked on how many USB3 root HUBs exist. You can test the current configuration via “lsusb -t”. The tree view will list each root_hub and “5000M” for USB3 speed. The “480M” is for USB2 configuration.

The problem with the dev carrier board is that the micro-OTG connector does not have the wiring to work as USB3…so even if there are more USB3 root HUBs available the dev carrier couldn’t use two. I have no other carrier boards so I’ve never considered to look for the maximum root HUBs for USB3…and you would need a separate root_hub for each camera…multiple ports would fail if your camera truly needs USB3 speeds.

According to your comment, it sounds you are going to have 3 ports on your carrier board, right?

According to internal team, we may only have one hub even with 3 ports.

Hi linuxdev and WayneWWW,

Thank you very much for your sincere support and helpful comments!

it sounds you are going to have 3 ports on your carrier board
Correct. I was thinking of making our own carrier board with three ports, and as a testbed before starting own design, I have a 3rd party carrier board which has two USB3 ports.

On the 3rd party board, I did “lsusb -t” and saw that their board had two USB3 ports under one USB3 root_hub.
I wanted to know if it came from their board design and configuration, or it was the nature of Jetson TX2 module itself.

According to internal team, we may only have one hub even with 3 ports.
Thank you for checking. If I understand correctly, it means that these three ports share 5000M bandwidth among them, right?


I appreciate for your great help.

You might consider custom PCIe USB3 if each port needs the full USB3 bandwidth.

Yes, that is correct. 3 ports sharing 5000M bandwidth.

Hi WayneWWW,

I was going through thread and i had same question. We are trying to select platform between JETSON TX2(3 USB3.1 Gen1, 3 USB2.0) and Xavier NX(3 USB3.1Gen1/USB3.1 Gen 2, 3 USB2.0).
As per your last statement, JETSON TX2 all 3 USB3.1 and 3USB2.0 share same bandwidth of USB controller i.e 5Gb/s, so we cannot connect 3 cameras which has bandwidth of 5Gb/s each to JETSON TX2 USB3.1.
For Xavier NX also all 3 USB2.0 and 1 USB3.1 also share USB controller bandwidth of 5Gb/s or 10Gb/s ?

Please clarify our queries for better selection of platform.



Please file a new topic on NX forum board for this.