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Thread: Transformerless Ethernet on T4.1 - disable AUTO-MDIX & Negotiate

  1. #1
    Junior Member
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    Jun 2022
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    Transformerless Ethernet on T4.1 - disable AUTO-MDIX & Negotiate

    I am working on an application with transformerless ethernet. The closest TI appnote I can find recommends turning off the autoMDIX and auto-negotiation. The DP83825 PHY datasheet says auto-negotiation can be disabled by pulling up the LED at boot with 2.49K.

    Auto MDIX can be disabled by pulling RX_ER high with 2.49K, but not an easy thing to solder. This PHY pin connects to the ARM chip. Is there any way to modify the teensy config so that this can be disabled by pulling this signal up at PHY boot, or would it be at PHY reset?

  2. #2
    Senior Member PaulStoffregen's Avatar
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    Nov 2012
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    Probably better to edit the library to use MDIO to configure the chip.

    MDIO lets you control all settings. Not sure which of the libraries currently has the MDIO code, but it's floating around somewhere. All the testing I did before NativeEthernet had the MDIO code configuring the chip, and I know for sure it does work.

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