Hello, I have a little problem with DP83848. I have built a PCB using Atmel UC3A and 83848 PHY, with a PoE supplied board. The connector is a Tyco PoE conn with magnetics. The strange think is that the 75 ohm resistors on magnetics common wire is missing. (See drawings: http://www.tycoelectronics.com/commerce/DocumentDelivery/DDEController?Action=srchrtrv&DocNm=6605834&DocType=Customer+Drawing&DocLang=English)When I connect the PCB to a Notebook, the Auto-Negotiation finds the good configuration, but when connect to a router, switch or hub, the negotiation fails.When I set up my Notebook's card to fixed 100BMit Full duplex, i can ping my panel property. I have tried the original Atmel firmware too, it works on original EVK1100, but my own panel with same firmware is wrong. It is possible, the auto negotiation error because the connectors missing 75 resistors? I have found a documentation with DP83848, PoE and external Magnetics without 75 ohms. (http://www.national.com/assets/en/boards/dp83848_demo2_schematicB.pdf)Thank you for your answersDavid
David,
The 75 Ohm resistors are part of a Bob Smith termination that is intended to reduce emissions caused by common mode signals on the CAT-5 cable. The lack of 75 Ohm resistors should not prevent link or cause functional problems.
Is the PoE solution part of the same board with the Atmel UC3A and the DP83848 or is it separate? When the board is connected to the router, switch, or hub, are there any signs that the board is receiving the necessary power? Can you access the devices? Do you see the expected LED functionality on the board?
Patrick
Hi Patrick,
Yes, the PoE solution works property. The Autonegotiation process fails with PoE and external power too. With fixed speed and duplex setup and connected to a switch, it drops periodically the link, but with a notebook or pc it works (link ready, ip stack ready, http server ready). It is maybe a setup problem on the DP83848?
The PoE power supply and the device is on same board.
Thank you
David
Could you provide the full register configuration for the DP83848 so that I could confirm the settings? If possible, it would also help if I could review the schematic for the design. If you would prefer not to post your schematic on the forum, you can email them to me directly at Patrick.OFarrell@ti.com
Hello,
are there any solutions for the issue above. I had exactly the same problem as David described in his post.
Andreas
Andreas,
The issue is still under investigation. Since there may be some subtle differences between the applications and in order to prevent confusion between the two, would you be willing to begin a new post and provide the details you have observed?
Hey Patrick,
thanks for you answer.
I tried to find out the reason for the issue and found out, that the problem exist only with the 100 Mibt/s interface. I tried to connect with only 10 Mbit/s an this works fine. I'm using the DP83630 with an Atmel AVR32 UC3A. I tested my code on the Atmel EVK1000 with the DP83848i and it works fine also with 100 Mbit/s.
The same code don't work at the DP83630.. but when I only allow 10 Mbit/s transfer mode it works..
There's no difference between Auto-Negatioion and forced mode..
The registers are set to the following values: