NANO's LAN ACT LED behavier abnormal

Hi Sir,

Using NANO SOM and setting on 100M LAN speed, the active LED still blinking when RJ45 removed.
SDK is reference’s SDK, LAN schematic as below,

ps, DY means dummy.

Besides, when RJ45 is unplugged, the register shows that this LAN still link-up.

If we change to use NX SOM with the same LAN schematic, the LED’s behaiver is normal.
Do you have any suggest for us?


When you put same module on nv devkit, does that LED act normally?

Hi Wayne,

Yes, LED act normal on nv devket.

But compare with devkit schematic, it seems 2 boards are the same design.

NANO_EVB_100M.log (83.1 KB)
Attachment is test process on EVB.

Insert RJ45 and then press enter.
If LAN link-up, it reports “0x794d”, and test result is pass.

Remove RJ45 and press enter,
If LAN link-down, report should be “0x7949”.

if we use this module on our CRB,
Remove RJ45, and it feedback error, and shows fail.

Or have others commandline can check LAN register status?


It looks more like your design issue since module works well on devkit. Maybe you should check the T1 design on your board, especially on capacitors, as seems the data lines status are wrong when unplug Ethernet cable, and so might cause the PHY can not detect the unplug.

Hi Trumany,

Did you means TX1 desgin?
Here are TX1 LAN schematic, are C198,C31,C199,C197 caps you mentioned?


I mean your T1 design. You should check T1 device datasheet or with the vendor to make sure your design is correct.

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