DP83869EVM: Help with Fiber-Electrical Conversion

Fnu Premsagar

Part Number: DP83869EVM
Other Parts Discussed in Thread: DP83869, USB-2-MDIO

Tool/software:

I have SFP1G-SX-85, that converts fiber to electrical and vice-versa. That is inserted/used in the DP83869EVM board; and I am using an Ethernet cable connected to the AM62b-p1 starter kit evm board (set it to static IP).

I have Windows connected via Ethernet to UMC-GA1F1T, which also has SFP1G in it. So the hardware connection looks something like this - PC>UMC-GA1F1T>DP83869EVM>AM62b-P1 board.

When I try to ping, it doesn't work, but when I replace DP83869EVM with UMC-GA1F1T, it works.

So my question is, do I need to do any hardware changes/configurations, like changing those DP switches or something, in order for it to work as mentioned above? (Totally newbie on this board.)

Currently on board I see LD2, LD4 and on and LDr is blinking. D1 is on with red-yellow in it, and all other 4 leds are on: 5V_Supply, FX3v3, VDDA2P5, and VDDIO.

2 months ago

0 Vivaan Jaiswal 2 months ago

TI__Expert 5835 points

Hi,

I wanted to confirm that I understand your setup correctly. From my understanding, you are trying to convert the copper (electrical) interface out from the PC to Fiber using the UMC-GA1F1T. The fiber output from this is then linked with the DP83869, which then is trying to convert it back to copper, and link it to the AM62B board with the onboard PHY. Is this understanding correct?

If so, I wanted to confirm first that the link status of the 869 is as expected, as well as the configured mode, which should be Fiber to Copper conversion. For this, you would need to read the registers 0x01, 0x6E, 0xC01. Please note that the latter 2 registers are in the extended register space, and need to be accessed accordingly (This link explains how to access them)

Best,

Vivaan

0 Fnu Premsagar 2 months ago in reply to Vivaan Jaiswal

Prodigy 110 points

I have USB-2-MDIO and got this reponse:

+1 Vivaan Jaiswal 2 months ago in reply to Fnu Premsagar

TI__Expert 5835 points

Hi Premsagar,

Thank you for the register values. If the 869 is trying to convert from fiber to copper interface, it is set to the wrong mode. The value 0x6E = 0x1000 shows that while mirror mode is enabled, the PHY is set to RGMII to copper mode, not fiber to copper mode.

Please refer to section 7.4.8.5 to switch the operating mode of the PHY to 1000M Media converter, which converts gigabit fiber to copper interface.

I also noticed that a fiber link was not established in the register value for 0xC01, but that should change after enabling the correct mode.

Best,

Vivaan

0 Fnu Premsagar 2 months ago in reply to Vivaan Jaiswal

Prodigy 110 points

Hi Vivaan, Thank you for pointing that out. I was looking for section 7.4.8.5, but I cannot find it in the datasheet. Could you please tell me what document you are referring to/want me to refer to?

0 Vivaan Jaiswal 2 months ago in reply to Fnu Premsagar

TI__Expert 5835 points

Hi Premsagar,

I am referring to this section of the datasheet linked below.

https://www.ti.com/lit/ds/symlink/dp83869hm.pdf#page=42

Best,

Vivaan

0 Fnu Premsagar 2 months ago in reply to Vivaan Jaiswal

Prodigy 110 points

7.4.8.5 1000M Media Convertor Mode

• Write 0x0044 to register 1DFh // Set Operation Mode to 1000Base-T to 1000Base-X

• Write 0x1140 to register 0h // Reset BMCR • Write 0x5048 to register 10h // Reset PHY_CONTROL

• Write 0x1140 to register C00h // Reset FX_CTRL

• Write 0x4000 to register 1Fh // Software Reset

Register 01DF is: 0000
Register 0000 is: 1140
Register 0010 is: 5048
Register 0C00 is: 0140
Register 001F is: 0000

I have used USB-2-MDIO, wrote the data to specific registers, and tested it, and it works. I was able to ping the am62b-p1 board. However, when I removed the power supply from the board and turned it on, the registers reverted to their original values, and it stopped working. Can you guide me with this?

+1 Vivaan Jaiswal 2 months ago in reply to Fnu Premsagar

TI__Expert 5835 points

Hi Premsagar,

Happy to hear that the setup is working!

Power-cycling the board has the same effect as a hard reset, upon which all the register values are reset. Because of this, any register programming done after boot are lost and the device returns back to its original default mode.

In order for the device to boot up with the correct settings for 1000M Media Conversion mode, the device must be strapped into this mode. I believe in this case, you need only connect a jumper on OP_MO[2] on the EVM. More information about EVM strapping can be found below. If configured properly, this should enable the device to boot up in the 1000M Media Converter mode so no register writes will be required for the device to function in this application.

https://www.ti.com/lit/ug/snlu237a/snlu237a.pdf#page=10

Best,

Vivaan

0 Fnu Premsagar 2 months ago in reply to Vivaan Jaiswal

Prodigy 110 points

Thank you, it worked!

0 Fnu Premsagar 2 months ago in reply to Fnu Premsagar

Prodigy 110 points

Just for Clarification: If I want fiber to RGMII, that would be the "7.4.8.2 RGMII-to-1000Base-X Mode" section, right?

+1 Vivaan Jaiswal 2 months ago in reply to Fnu Premsagar

TI__Expert 5835 points

Hi Premsagarm,

Yes you are correct, fiber to RGMII would be the RGMII-to-100Base-X Mode.

Best,

Vivaan

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DP83869EVM: Help with Fiber-Electrical Conversion