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DP83826I: TX RX connection issue

Allen Lu
Intellectual 2440 points
Part Number: DP83826I

Tool/software:

hi team, 

My customer using the DP83826 phy with ESP32 for ethernet connection here.

and customer feedback there is a issue when pairing with different router. then we finish below test for double check ：

1.  ping test  for a day within 0 Packet Loss Rate， but only cannot get IP sometime.

2.  Eye diagram test passed

then we start analysis the system as below and found the cause here. after customer use the correct 4pin cable, all router can get the IP.

but customer already have some production ship to the market with such wrong order TXRX order.

 can you help to share the risk and how it works sometime with wrong connection order with some router here?

  • 0
    TI__Mastermind 39775 points

    Hello,

    Traditionally, Auto-MDIX would alleviate this issue. Is this being enabled in PHY?

    Else, if using reversed cable, would setting manual MDIX work?

    Sincerely,

    Gerome

  • 0 in reply to Gerome Cacho
    TI__Intellectual 2440 points

    Hi Gerome,

     Tks for the support here.

     As check with the customer here. they use at BASIC Mode.  And basic mode show it can not support the Auto-MDIX and Force MDI/MDIX .  does it means customer can only change the 4pin cable but not work with Auto-MDIX function.

    additionally, checking this register ,why BASIC Mode show: Default to A-MDIX enabled. it is confuse with above function. can you help to explain? 

  • 0 in reply to Allen Lu
    TI__Mastermind 39775 points

    Hi Allen,

    These diagrams mean that Auto-MDIX should be on by default in the DUT in Basic Mode. Therefore if there are no register configurations done, this should still be active. Is the link partner also showing Auto-MDIX capabilities? If the link partner is not, this would also explain the sensitivity to cable type as PHY would have no choice but to lock into a configuration.

    Sincerely,

    Gerome

  • 0 in reply to Gerome Cacho
    TI__Intellectual 2440 points

    HI Gerome,

     Still not clear to understand. regarding to the description of  yellow mark as below :

    "

    、

    Auto-MDIX Enable:

    BASIC Mode: Default to A-MDIX enabled.

    ENHANCED Mode : Latched by strap A-MDIX

    0h = Disable Auto-Negotiation Auto-MDIX capability

    1h = Enable Auto-Negotiation Auto-MDIX capability“

    what`s the DUT represent here? 

    if DUT means the  PHY like DP83826,  then the DP83826 should enable the auto-MDIX function  in basic function? but the basic function can not support the auto-MDIX.

    If DUT means the link partner like router,  we cannot control whether they can enable the AUTO-MDIX or not , it is a black box to us. we can only identify whether we can get IP here.

    Gerome Cacho said:
    Auto-MDIX should be on by default in the DUT in Basic Mode.

    besides,  the BASIC mode can not support  AUTO-MDIX, if we set the register as enable, can we still enable the AUTO-MDIX in basic- mode?

     

    For example, the register have the default setting as :

    //PHYCR register
    #define DP83826_PHYCR_MDIX_EN 0x8000
    #define DP83826_PHYCR_FORCE_MDIX 0x4000
    #define DP83826_PHYCR_PAUSE_RX_STATUS 0x2000
    #define DP83826_PHYCR_PAUSE_TX_STATUS 0x1000
    #define DP83826_PHYCR_MII_LINK_STATUS 0x0800
    #define DP83826_PHYCR_BYPASS_LED_STRETCH 0x0080
    #define DP83826_PHYCR_LED_CONFIG 0x0020
    #define DP83826_PHYCR_PHY_ADDR 0x001F

    in this case, the  PHYCR Register bit15 set as 1, means 1h = Enable Auto-Negotiation Auto-MDIX capability.

     so base on this case, does it means if we enable the basic mode , the auto-mdix will disable internally?

  • 0 in reply to Allen Lu
    TI__Mastermind 39775 points

    Hello,

    Allow me to clarify. In basic mode, Auto-MDIX should be enabled by default with no option to strap into disable. This is why you see the bit high in the register when you read. You may test with link partners that have auto-MDIX on, as well as auto-MDIX off to verify the desired behavior. For Robust Auto-MDIX, it states that when DUT is force MDI/X, this shall also be enabled for best practices with other link partners in the market.

    Sincerely,

    Gerome