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AM625: How to Configure RMII Mode

Kevin Peng
Expert 3432 points
Part Number: AM625

Tool/software:

Hi TI Experts,

Customer is working on AM62x SDK9.2.

Now they could run Ethernet applications with RGMII on their development board successfully.

Due to they use RMII phy in the old AM335 platform, and they wish to keep at RMII in AM62x also.

We have not yet found a clear guide for how to configure the DTS file to enable the RMII mode in AM62x.

Customer has tried the below configurations in the DTS, but still not make it working.

Could you help check if this is sufficient for the RMII mode configurations? 

Many Thanks,

Kevin

  • 0
    TI__Expert 3432 points

    Hi TI Experts,

    Customer finally bring up their first batch of AM62x boards, and could use RMII mode successfully.

    As their first batch of board did not have impedance matching for RMII signal line. Customer recently did the new design, in this redesign, they have added impedance matching, but there have been issues shown below. 

    We checked the ifconfig, and the link is up.

    And we checked the ethtool, and found that there is rx_align_code_errors and CRC errors below.

    I checked the ethernet debug application note below.

    https://www.ti.com/lit/an/spradj8/spradj8.pdf

    And it seems that this might relate to the layout. And customer has confirmed that they use the same SD card on the first batch of boards and this new patch of boards, which means the SW is exactly the same.

    Hence, we doubt that when customer adds impedance matching on RMII side in this new design cause some problems. So please see the RMII schematic for the first batch of boards and new batch of boards separately below.

    First batch of boards

    New design

    I also attached the new PCB schematic in the private email.

    Please help check if there is any susceptive points especially on RMII side in this new design.

    Thanks,

    Kevin

  • +1 in reply to Kevin Peng
    TI__Guru**** 174754 points

    Hi Kevin

    Please make the below changes and test

    I see customer using 33R for TDX as well as RDX on the carrier board.

    Can you please suggest customer to change the TDx series resistors on the carrier board to 0R

    regards,

    Sreenivasa

  • +1 in reply to Kallikuppa Sreenivasa
    TI__Guru**** 174754 points

    Hi All,

    Reply from customer

    Customer found there is also a 33 ohms resistor on the carrier board, and if they reduce the resistor value, the RMII could work normally now

    regards,

    Sreenivasa