Hot!Ethernet Troubleshooting

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Jim Nickerson
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Re: Ethernet Troubleshooting 2018/02/20 16:37:13 (permalink)
post to try to fix blinking on page 3
edit: and it works, no more blinking
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Re: Ethernet Troubleshooting 2018/02/21 07:07:42 (permalink)
I have a board with the LAN8740A, don't know about differences to the LAN8720A. I'm using MII.
I have posted the schematic here about 1 to 2 weeks ago, maybe that helps.
Are you sure that you used the same RJ45 (with integrated magnetics)? There are so many variants, it can be confusing (at least for me).
For the supply voltage, I can measure a bunch here if you want.
Until now, only one board was DOA in regard to ETH. But the reason was visible: A big blob of solder.
Feel free to ask, if my LAN8740A is of any help.
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Re: Ethernet Troubleshooting 2018/02/22 07:12:55 (permalink)
@matta, I have tried to understand your last post, It isn't very clear.

Erik Friesen
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Re: Ethernet Troubleshooting 2018/02/22 07:35:36 (permalink)
Apologies, I think I did a poor job of explaining.
To summarize previous posts, I had a working implementation of ethernet on a PCB that I assembled myself. I then had some assembled professionally and when they came back they didn't work (never auto negotiated, didn't respond when ethernet cable was plugged in).
As it turns out, I made a mistake when I assembled the first one and had a bad solder joint on one of the 50 Ohm termination resistors to Vdda. It just so happens that this is what made it work while the others do not. When I take off all the 50 Ohm Terminators and replace them with 100 Ohm everything works as expected on all boards. Now I just need to figure out why that is the case, since I am sure it is some other thing I have done wrong.
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