We are designing a custom Jetson Xavier NX carrier board and we want to integrate a network switch (Microchip 7-port Gigabit Ethernet KSZ9477). The input interface of the switch is SGMII (serial gigabit media-independent interface) or RGMII.
However as far as we know, the outputs of the module SoM Xavier are only MDI pairs.
So integration of ethernet switch is not possible? Could you confirm this?
Could you suggest a solution to have 2+ ethernet ports on a custom Xavier Carrier Board?
Thanks and best regards,
Kien
P.S. We found a related post but not sure if there is new update:
Sorry, there is no update. There are several alternatives:
Use Xavier AGX 8GB modules. They are more expensive (and the 8GB modues are being discontinued in favor of NX), but they provide RGMII. By using the 32GB Xavier AGX modules you may get away with fewer nodes at the expense of higher cost per node
Use the single-lane PCIe port or the USB 3.0 port to connect an external ethernet controller chip. I’m not aware of controller chips without PHY, however.
Try coupling NX board and switch PHY ports with standard ethernet transformers. I’d buy a cheap 5-port switch and a couple of cheap PCIE network cards remove the jacks on the switch and the jacks and transformers on the cards and connect them with short twisted pair cables.
The Jetson Xavier NX module provides MDI paris output with a RTL8211F PHY on module.
Jetson Xavier AGX modules provides RGMII interface.
The USB or PCIE to Ethernet or coupling NX board MDI pairs and switch PHY ports are good choice.
Thanks a lot @fchk and @edli1983!
Since USB is reserved for other purposes, I’m more interested in the coupling option.
I’m not so familiar with the concept. Is that the transformerless / capacitor coupling on the custom PCB as described in some Application Notes such as Micrel/Microchip:
Then coupling 3 MDI pairs of NX board to 3 pairs of a PHY port on the switch IC should probably work?
On the switch IC (KSZ9477S in this case), should I choose the PHY host port to be Differential Data Port (port 1-5) or MII port (port 6)?
I’d avoid capacitive coupling. Some device use current mode, some use voltage mode, and your circuit has to accomodate the different kinds of controlling the lines. Remember: The MDI signals are standardized only AFTER the transformer - what happens BEETWEEN PHY and transformer is up to the vendor.
It’s easier to get a transformer like
connect pins 1-8 to the LAN device as per lan device vendor specification and connect 9-16 to the switch chip as per switch chip vendor specification.
As I have written before: try it out first with a cheap switch and cheap network cards and PCs etc. in the lab.
we have designed the custom carrier for NX module with Ethernet switch KSZ9897 there. We added KSZ9031 as an interface between KSZ9897 and NX. We used capacitive coupling between KSZ9031 & NX as per microchip guidelines
Hi @smarty
We have designed and tested the capacitive coupling directly between KSZ9897 with Jetson NX and it works fine.
Take care to follow the High speed design guideline from Nvidia Product Design Guide.
Yes to Port 1 of KSZ9897. I didn’t need to configure KSZ9897 internally, just used the default config. Just follow the Evaluation board design of Microchip and it should work.
For a custom NX carrier board ethernet lines, when using externl magnetics, does the design needs pullup resistors for the ethernet differential lines ?
some manufacturers designs include pullups resistors to a BIAS voltage, but the NX datasheet doesn’t refer to that subject.
Thank you
