SCM20100E module and Ethernet

SITCore Modules & Chipsets
#1

I have created a custom board using the SCM20100E module with POE Ethernet and I’m running into a strange issue where everything is working perfectly except when I change the link speed on my switch to 10 FDX (full duplex) it will not establish a link (100 FDX or auto works fine).

Using my SC20260D Dev board this change works exactly as expected. The speed led goes out and the link is established in 10 FDX. Using the exact same code, except for replacing the pin references, the development board works exactly as expected. I have also tested this without including any POE components or ESD protection and the results are exactly the same. This leads me to believes it has to do with the MagJack ethernet connector I selected or my configuration.

Does anyone see any reason the following TRP/ Bel ethernet connector with built in magnetics would not work with the SCM20100E module (or my configuration)?

https://www.mouser.com/datasheet/2/643/ampis77903_1-2289808.pdf

Here is the schematic for the board:

schematic
schematic1465×815 97.7 KB

#2

I don’t know if this has anything to do with it but ETH_LNK and ETH_SPD outputs from the PHY are also AN0 and AN1 strap option inputs. Depending on how the LED’s are wired they are read at boot up and it determines the Auto-Negotiation options. What have have looks right but it might be worth investigating.

https://www.ti.com/document-viewer/DP83848K/datasheet/detailed-description#SNLS2507174

#3

Thank you! This is very helpful as I did not realize this connection. I think you could be on to something. Let me dig in to it. I just assumed they were status only.

#4

Thank you very much for your advice. You were spot on. I now have a fully functional board and the ethernet speed is working perfectly. :smile:

IMG_0386
IMG_03861719×1866 443 KB

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#5

Very nice board ! Do you sell it ? I see “open source hardware” on it, do you have the layout published ?

1 Like
#6

Yes this is an open source project. It was created using Altium CircuitMaker and the boards were fabricated at www.jlcpcb.com. I also have a github project too but I’m not quite ready to make it public as the code needs some clean up. I also have a 3d printed case for it that I’m wrapping up and will published too.

I was not planning on selling them. However, I have made a few minor changes to the version pictured above and was planning in the next few weeks to assemble a final version. Direct message me If your interested in a hand assembled board. I would be willing to build an extra one.

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