Advice for connecting multiple TX2 modules on a single pcb via GigaBit Ethernet

Dear Sirs,

I’m designing a custom carrier board for multiple TX2 modules on a single pcb - a single module does not have enough power to handle all the computational tasks. These modules need to talk to each other via Gigabit Ethernet.

Unfortunately, GMII, RGMII, or SGMII is not available on the TX2 connector, only the PHY’s MDI pairs.

What is the recommended way to connect the TX2’s PHY signals to an Ethernet Switch chip? Capacitive coupling via 100n 0402 X7R capacitors as I’ve seen in some appnotes for transformerless fast Ethernet coupling? Inductive coupling via a single 1000BaseT Transformer?

The switch chip would be a Micrel/Microchip KSZ9567R (http://www.microchip.com/wwwproducts/en/KSZ9567), unless there is a good reason to use something different.

Space constraints are tight, so I’d prefer a small and lightweight solution.

Best Regards

Frank-Christian Kruegel
OptoPrecision GmbH, Bremen, Germany

Hi fchk,

As you see, there are only MDI pairs exposed, the RGMII is only in the module. The transceiver is BCM89610.

Hey,

Were you able to get this working? I would be very interested in how this turned out for you.

Thanks,
Mat

We have a similar issue and would like guidance from Nvidia on this topic.
We are trying to integrate a KSZ9897STXC switch with the Ethernet on two TX2s. We can get 100 Mbps connectivity, but can not sustain 1000Mbps. We are currently experimenting with two development boards before committing a design to hardware.

Would Nvidia provide guidance on network switches that are known to work at 1000 Mbps with the Jetson Tx2?

Thanks!

We’re not connecting multiple TX2s together, but we are using this on our custom PCB for Ethernet.

https://www.nxp.com/docs/en/data-sheet/SJA1105.pdf

This is one we have not looked at yet. Thanks so much!

I am not sure if I see the correct answer. Is it transformerless /capacitor couple? I have similar topic for the Nano. It only exposes the MDI pairs. Can the interface to a BroadCom chip be transformerless? Thx

We skipped this problem and went from the original dual TX2 Design to a single Xavier AGX design after AGX was available.

However, plase have a look at

https://community.broadcom.com/HigherLogic/System/DownloadDocumentFile.ashx?DocumentFileKey=8f7fd14b-7a73-4b40-b238-59a3d32c98ed&forceDialog=1

Page 22-23 might be for you.

The topic I created as " RTL9119I Ethernet controller interface. I was more concerned with the Nano side. I know the BCM switch will support the transformerless, but does the MDI pairs from the Realtech part RTL91191 need to support? Or it only apply to BCM switch? Thx

Hello Fchk: did you solve this problem? I need connect NANO to SJA1105, have the same concern, thnaks

Hello , I use SJA1105—KSZ9031----JetsonNANO, with AC coupling direct link ,does this work for this kind of connection?

The output interface of PHY is MDI, it is connected to magnets/RJ45.

Do you mean KSZ9031 support MDI port, so you want to connect it to nano module in MDI directly? This kind of design is not validated on nano, you will have to handle it by yourself, suggest to check with vendor of KSZ9031 first.

KSZ9031 support both MDI and MDIX mode,it should be feasible to connect MDI to MDIX with direct link normally.

2 points what I want to confirm, I think this concern is partly due to short of design material from Jetson NANO inside.
1). Here use 1000M ethernet, different from the 100M, how to connect 4 pair differential lines? From the datasheet of KSZ9031, youcan easily get from website, the TXRXP/TXRXM definition, can be connected directly to GBE_MDIx_P/GBE_MDIx_M in the schematics screensnap I show before?
2). Inside Jetson Nano, the PHY is current driving or voltage driving? what’s the I/O voltage level, KSZ9031 side I use 1.8V I/O level , is that compatible with 10nF ac coupling capacitor? Should I keep the pull up with 49.9R on eachline?

Again, it is not validated on nano, we have no suggestion on this kind of design.

The pin IO voltage info is in pinmux sheet. For other questions, we have no answer as not tested/validated.