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TM4C129XNCZAD: RMII to custom ethernet switch IP - No phy

Joseph Orender
Intellectual 260 points
Part Number: TM4C129XNCZAD

Hello,

We have implemented a TM4C on our custom board with no PHY and connected the RMII interface directly to the FPGA. I connect the reference clock and RMII interfaces directly together from the TM4C to the ethernet switch IP in a crossover pattern - tx<->rx and tx_en<->crs_dv. We have made some minor changes in LWIP such as adding netif_set_link_up(psNetif); to the end of the initialization function right before we call to begin an autonegotiation cycle. We have 10 TM4C devices on the board and the number of devices that will join is usually around 60-70% network join percentage and totally random who decides to join. 

I am wondering if there are numerous lwip changes that need to be made if there is no phy involved. Since there is no phy and MDIO interface, we were commenting out the reads and writes to the MDIO table. How can we determine if the link is up if we dont have a phy and cannot ask the phy from the MDIO interface if the link is ready?

Hoping you can help. Thanks a bunch. 

-Joe

  • 0
    TI__Guru 72500 points
    Since the RMII interface was designed to use a PHY, I don't know. Is that not a question for the designer of your custom Ethernet switch IP?
  • 0 in reply to Bob Crosby
    Intellectual 260 points

    "Since the RMII interface was designed to use a PHY, I don't know."

    Very insightful.

    "Is that not a question for the designer of your custom Ethernet switch IP?"

    No. The ethernet switch performs very well with various other MAC to MAC connected hardware devices as well as a "soft" device coded in verilog and connected inside the fabric with an RMII crossover.

    There are plenty of reference designs found with a quick google search that connect an two RMII devices together MAC to MAC. The question is more along the lines of how to tell the MAC in the Tiva that its speed is 10 or 100 and that the link is up or if there are any custom lwip parameters on top of the already custom tm4c interface that need to be made.

    -Joe

  • 0 in reply to Joseph Orender
    TI__Guru 72500 points
    Sorry, as is painfully obvious, my knowledge of this is too small. Perhaps some other users will add helpful comments. Otherwise, I suggest you search:
    savannah.nongnu.org/.../
    LWIP is provided in TivaWare as a convenience, but is not TI software.