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Unable to get DP83822EVM to function

Scott Streit
Prodigy 40 points


Hello, I have a DP83822 evaluation board that I cannot get the computer to recognize.  I started by following the instructions in the User's Guide for quick setup operation.  The J6 jumpers are set for AVD_INT, CT_INT and VDDIO_INT. The J10 jumper is set for PU ( Link/Act ) and the J2 jumper is set for 50MHz. When I plug the USB cable in, the AVD_LED and VDDIO_LED lights go on. Next, if I plug the Ethernet cable in and connect the other end to a computer, nothing happens. It's like the board doesn't exist.  From what I can tell, this should be enough to have the computer recognize the board.

The next step I tried, is connecting the Ethernet cable to our local network, but the router never showed the board in it's list of connections and the Link/Act light never came on.

Finally, I tried connecting the board to our MAC, which is an NXP 4330 processor using lwip ( lightweight IP ).  In this way, I am able to read/write the SMI registers, but the board is still not recognized by the computer.

Any suggestions would be greatly appreciated.

-Scott

  • 0
    TI__Mastermind 23675 points
    Hi Scott,

    It is because you are operating the board with a 50MHz clock source but not configuring the PHY to do so. The PHY is configured for 25MHz MII operation. You have three options to fix the issue you see:
    1. Place the jumper for 25MHz operation and power cycle the board so that the on-board CDCE is configured properly.
    2. Configure the 822 for 50MHz operation using pull-up and pull-down resistors that you will need to solder onto the open pads. *Please see the datasheet for the pin configuration bootstraps. You will need to set RX_DV and then use the User's Guide to find the pad location to add the resistors.
    3. Configure the 822 for 50MHz operation using SMI (MDIO/MDC). Register 0x0017 controls the 25MHz/50MHz operation.

    Kind regards,
    Ross
  • 0 in reply to Ross Pimentel
    Prodigy 40 points
    Hi Ross,

    Thanks for your quick response. I found out from the engineer who gave me the eval board that it uses a 50 MHz external clock. He took the board and populated it according to your suggestion #2, so that the chip boots with RMII and 50MHz. Our NXP processor interface can only support RMII. I verified that the SMI register 0x17 says the PHY is set for RMII and 50MHz clocking. However, the computer still does not see the board at all. Is there anything else I can look for? Thanks.

    -Scott
  • 0 in reply to Scott Streit
    TI__Mastermind 23675 points
    Hi Scott,

    What is the value of register 0x01, 0x17 and 0x19? What are the register readings for 0x467 and 0x468. These registers will let us know what bootstrap setting the PHY is in.

    Do you have access to an oscilloscope? I would also like to have a look at the link pulse (if you are doing auto-negotiation or 10Mbps forced) or the MLT3 eye (if 100Mbps forced).

    Kind regards,
    Ross
  • 0 in reply to Ross Pimentel
    Prodigy 40 points

    Hi Ross,

    Sorry for the delay in response.  A broken resistor on our MAC board resulted in a loss of the external 50MHz clock.  We finally sorted that out and now the host computer can sort of recognize the board.  It will swap between creating a 10 and 100MBs link to the board.  We are supposedly setting the bootstrap to RMII and 50MHz.  Here are the register values you asked for:

    Reg 0x1 = 0x7849

    Reg 0x17 = 0xE1

    Reg 0x19 = 0x8021

    We tried to look at the incoming signals with an oscilloscope.  We can see clean signals, but we don't have the experience to know exactly what we are looking for.

    As a side note, if I download a program into our NXP processor, which acts as the MAC, the board will randomly appear and disappear from the host computer list of network connections.  It looks like the processor somehow interferes with the DP83822.  I'm not sure if that's relevant, but I thought I would mention it.

    -Scott

  • 0 in reply to Scott Streit
    TI__Mastermind 19780 points
    Hi Scott,

    Is the 50MHz reference being used for the DP83822 synchronous with the MAC? I'd suggest connecting the EVM to the PC without using the NXP MAC attached to the EVM.

    Your PC will show an unidentified network when only the EVM is connected. Without upper IP layers active, there will be no network handshaking/identification.

    Regards,
  • 0 in reply to Rob Rodrigues
    Prodigy 40 points

    Hi Rob,

    The 50MHz clock is synchronous with the MAC.  The board can now be seen by the host computer.  When I first plug the cable in, the computer will select, seemingly randomly, 10 or 100MBs for the link speed.  I used an oscilloscope to verify that there are clean looking signals on the RMII lines between the NXP and the DP83822.  I am beginning to think that I now have a initialization problem.  All ping requests to the board fail when I run tcp/ip echo code on the NXP.  Is there a driver library or example code for the DP83822?  I am using a driver that was originally meant to operate a LAN8720.  The driver code only reads and writes from the MDIO registers and appears to work since I can read and write the registers on the DP83822 just fine.  I am at an impasse now because I cannot make the NXP communicate over the DP83822 PHY to the host computer. Do you have any idea or suggestions?  Thanks.

    -Scott

     

  • 0 in reply to Scott Streit
    TI__Mastermind 19780 points
    Hi Scott,

    Yes this sounds like an initialization problem. The DP83822 does not have a dedicated driver library but uses the generic Linux PHY driver for intialization. Depending on how the LAN8720 driver configures the device, there may be some mismatch.

    Because the settings appear to be random, I'd suspect that the NXP 4330 is pulling the RX_D0 pin and causing the 822 to strap in different auto-negotiation modes. See the AN_1 strap bit in the DP83822 datasheet. This is why I suggest disconnecting the MII/RMII fromt he processor to the EVM and establish a link between the EVM and PC.

    Best Regards,