Still having major problems with the Ethernet interface

We’re still having problems with EMX units failing after being powered down and up again. We have made 25 units and so far 6 or 7 of them have had the Ethernet interface fail. When the device powers up we just get a solid light on the jack and the other one flashes slowly about once a second and we don’t get a link on the switch. We have just received a shipment of 130 EMX modules today and I’m seriously considering sending them back!

You better contact GHI directly if you ordered such a volume.

As answered in email. Your issue seem to be related to your PoE circuit. The modules you revieve are the same ones we use on thousands of fez spiders and we ship to many other customers.

Please let us know if you have any questions.

I think Gus is right. I had a similar issue with a specific design and it turned out to be a problem with my power supply circuit. It wasn’t providing 3v3, but just above 3V which is too low for the EMX to start properly. Have you measured the supply voltage on the module?
If you could share the schematic for your POE circuit, I might be able to help.

Hi Nick,

The PoE circuit is provided by a Silver Telecom AG5000 module, it’s not one we built ourselves. The output from this is 12V which powers a switch mode POL module which provides the 3.3V. We’ve checked the voltages using a scope and the 3.3V output stabilises at about 3.24V following a rise from 0V over about 3.7ms. This voltage and start-up sequence is exactly the same on working boards and non-working boards. The LED sequence that it is displaying obviously means something as it’s a regular pattern, can anyone say what it is indicating?


There is also the magnets and diodes that okay a big part of the phy functionality.

Hi Edward,

When I supply 3.24V to one of my EMX modules, it won’t start all the time. Sometimes it does, sometimes it does not. When I increase to 3.3 it always works. Have you tried to provide power from another source?

I don’t know the POE module that you are using. Neither can I say anything about the led sequence you are describing.

Hi Edward,

I’m also using a silvertel module AG5100, to provide power supply to my chipworkx. Til then, I’m using the eval board published by silvertel that provide 12Vcc, and then plug it in my chipworkx devkit. All seems to be fine. Maybe you should get back to the devkit schematics and implement the same logic that is done there…

Hope this will help…

Hi Gus,

Sorry for the delay but we’ve been out at our customers site trying to install the first units that we made. We’ve now had 10 of the 30 units fail in the same way.
I’ve attached the schematic details of the Ethernet circuit of our board.

I’ve spoken to Silver Telecom about their PoE module and they manufacture them in batches of 10K and have made hundreds of thousands of them, they supply large manufacturers such as Samsung for use in PoE cameras and to do this they have had their design and manufacturing audited many times. So I’m ruling the PoE module out as a problem at the moment.

We need to get this issue resolved asap as we have to build the next 150 units within a few weeks! We can send you one of the faulty units if you want.

What’s our next step?


Send a good unit, faulty unit, and schematics to my attention to the address on contact page. my email is gusi@ GHI’s domain.

This is of course is beyond our free support but I realize how frustrated this can be and we are willing to take a quick look.

@ EdouardH,

I had a brief look at your first shiled schema, and something seems to be strange to me…

No problem with the way you extract your Power line, but regarding to the Data part, can you detail a bit more what are the components you’re using (CMC1 and CMC2). In the
typical system diagram provided by Silvertel, the secondaries of DC conversion do not have 3 pins, but only 2 : TX+, TX- and RX+, RX-. So what are the pin called TDP and RCT ?

Hope this will help…

I am using Silvertel as well. Works great!

Here is the schematic of my module:

@ Architect,

I also noticed that in your case, RCT and PCT are connected to VCC, that we do not see in the schematic provided by EdouardH.

Can you provide me with the part reference of your TYCO module (difficult to decrypt on the image), that seems to be much more interesting than using seperate components for isolation. Is it integrated to a plug ?

Thanks in advance !

No problem!

Yes, it is in the plug. Was hard to find the right one, but here it is:

[quote]I also noticed that in your case, RCT and PCT are connected to VCC, that we do not see in the schematic provided by EdouardH.

I think it is in the second image.

Thanks a lot !

I keep it in mind, nice price also…

Yes… you’re right ! :-||