DP83822I: Link never getting established when ethernet cable connected

Hi Wilmer, 

Are you using two DP83822's as link partners? If so, let me know what the PHY Address is set to for each. If they are the same, please try changing one. You can also try resetting only one of the PHYs. Let me know the results of this test. 

Thanks,

David 

I am not using two DP83822's, only one connected directly to a router.

Hi Wilmer, 

What is the history of this board? Was it ever working? How often does this "intermittent occurrence" happen? Does resetting the PHY have any effect?

Are you able to connect the DP83822 board to any other link partners and establish link? Is the router able to establish link with any other link partners?

Let me know the answer to these questions.

Thanks,

David

The issue occurs almost randomly. When it does it lasts for a few days. Resetting the PHY does not help. Resetting the entire device does not help. 

I've tried multiple APs/Routers and the issues occurs there as well. I will try to capture the register data if/when it starts working again and hopefully there will be a hint there.

Hi Wilmer,

Are any changes made when it starts working again? Or it randomly starts working for a few days before breaking again? Has this issue been happening since the boards creation, or is this behavior new?

Also, do you have any other copies of the board you can try? If so, do they see this same random issues? 

I can take a look at your schematic as well if you send it.

Thanks,

David

No, changes, no. I'm suspecting this means it's hardware related.

Yes, it's been happening since the boards creation. This happens on many devices. It's possible it's the switch that it's connected to; but other devices connected to the switch are working fine (@ various duplex modes and speeds), so I'm unsure how to verify. I've shared the schematic privately.

Hi Wilmer,

Received. I will look through it and get back to you next week. 

Thanks,

David

Hi Wilmer, 

I sent you my comments on your schematic privately. Has the board started working again yet? If so, please send the new register dump.

Either way, please read registers 0x0467 and 0x0468 so I can check that the device is being strapped correctly. Note theses are extended registers, so you must follow the procedure described in section 8.4.2.1 of the datasheet to read these.

Thanks,

David

Has not started working again. So can't get the main registers yet.

Register 0x0467 = 0x0F40

Register 0x0468 = 0x0F40

I will have more information on the schematic comments later this week.

Looks like this means only 10/100 Half-duplex is enabled; which is odd. Full duplex should also be configured.

Has not started working again. So can't get the main registers yet.

Register 0x0467 = 0x0F40

Register 0x0468 = 0x0000

I will have more information on the schematic comments later this week.

Looks like this means only 10/100 Half-duplex is enabled (on par with the ANAR register); which is odd. Full duplex should also be configured.

Hi Wilmer, 

Pin 17 should be in Mode 4 in order to advertise Full-duplex mode. Please change the 2.49k pulldown resistor to a pullup. 

Another thing to try is to manually force 100mbps, full duplex, and mdi/mdix. You will have to manually set the link partner to this configuration as well. 

Let me know the results of these tests.

Thanks,

David

That's interesting, we have seen our devices with this HW configuration be detected as Full Duplex before. In any case this wouldn't effect the link establishment capability, correct?

How can I manually force these settings? Would this require additional HW changes?

Hi Wilmer,

If the link partner is only advertising full duplex capability for some reason, then this would prevent a link up, so recommend to change the strapping resistor as mentioned.

One interesting thing is register 0x0006 and 0x0005 show no link partner auto-negotiation capabilities. Can you try connecting two of these boards together to see if these registers are different?

Since this seems like an Auto-MDIX issue, first I would like to try disabling auto-mdix, but leaving auto-negotiation on. To do this, set bit[15] of register 0x0019 to 0, and set bit[14] to the relevant value. Are you using MDI or MDIX?

Then you can try turning auto-negotiation off as well. To manually force 100Mbps, set register 0x0000 bit[12] to 0, bit[13] to 1, bit[8] to 1. You will also have to set bit[5] and [6] of register 0x000B accordingly. You must set this same configuration on the link partner as well. 

Thanks,

David

- Link partners are always configured for auto-negotiation, which is on by default on this PHY transceiver as well.

Device connected to Network Switch (auto-negotiation enabled):

Hi Wilmer,

You may be right, sounds like a hardware issue. You can use a copy of our EVM as a known good board to confirm this if you would like. Otherwise, there is not much other information I have to go off of right now, so will need your help to narrow down the condition of failure. 

Thanks,

David

Hi WIlmer, 

Glad you figured it out. Will close the case.

Thanks,

David