Linux/DP83822HF: DP83822HF FX Not working.

Hi,

Thank you for your reply.

I need to operate DP83822HF in FX mode.


Q2. I wrote 0x4000 to the CR register, but it didn't work.
Are there any other settings besides FX_EN?


Best Regard,
John

Hi John,

You should only have to set bit[14] of the register address 0xA to get FX mode enabled. You said you write 0x4000, but there is a reserved field that should NOT be modified.

Please read the default value of 0xA register, then set bit[14] and do not change any of the other bits.

Could you also provide a schematic of only your PHY?

Best Regards,

Hi Rodrigues,

I am already set bit[14] and do not change any of the other bits.

 

CR2 Reg val is 0x4100.

Are there any other settings besides FX_EN?

------------------------------ reg set code ------------------------------------------------

val = phy_read(phydev, 0xA);

val |= 0x4000;

phy_write(phydev, 0xA, val);

-------------------------------------------------------------------------------------------------

Schematic file.

PRU2_1_FX.PDF

==== DP83822HF_read_status 761===

BMCR(0x0): 0x3100

BMSR(0x1): 0x7849

PHYIDR1(0x2): 0x2000

PHYIDR2(0x3): 0xa240

CR1(0x9): 0x0

CR2(0xa): 0x4100

PHYSCR(0x11): 0x4100

RCSR(0x17): 0x41

LEDCR(0x18): 0x400

PHYCR(0x19): 0x21

GENCFG(0x465): 0xffffffea

=================

Best Regard,

John

Hi John,

It looks like you are setting register 0xA properly but I do have 1 concern. Your schematic shows a bead and a 10nF cap only for the PHY. Please implement the cap decades required by the DP83822 datasheet.

It may be possible that as you switch from TX to FX mode, the PHY is starving for current and causing a failue.

Can you also strap the PHY into FX mode rather than change the register? You could also remove the bead from your design and replace it with a 0ohm resistor.

Best Regards,

Hi Rodrigues,

I tried both(FX Boot strap / DP83822 Datasheet guide).

but, FX Mode is not working.

I have question.

how to configuration 'PECL termination resistance' of DP83822HF

 

Best Regards,

John

Hi Ross,

I tried both(50 ohm / 0.1uF cap).
but, FX Mode is not working.

When trying to read register 0x0001 Basic Mode Status Register through MDIO the result is 0x7849 which denotes that the link and auto-negotiation bits are off. The LEDs show that the link and auto-negotiation have been completed.

There is a similar case.
URL: e2e.ti.com/.../2032488

But I don't know why read 0x01 register requires two reads.
Is this a connection to this problem?

Best Regards,
John

Hi John,

BMSR requires 2 reads because the link bit is latched low for debug purposes. You must always read BMSR twice to see the link status.

Best Regards,

Hi Rodrigues,

I tried 2 reads. (BMSR:0x7849)
but FX not working.

Is there any other solution?
Please advise me.

Best Regards,
John

I don't know SFP module signal.
and
i want to know wave signal about SFP module between phy(TD+, TD- , RD+, RD-).

Best Regards
John

Hi John,

One of your problems may be your SFP has a LOS signal. In the diagram you posted earlier in the thread, the SFP shows a LOS or loss of signal pin. The DP83822HF supports a SD pin or signal detect.

The LOS output from your SFP must be inverted to provide the proper SD input to the DP83822HF to indicate a link is available across fiber. You can do this by changing bit[0] in register 0x465 to 1.

Also, which mode are you strapping the RX_ER pin to?

Best Regards,

Hi Rodrigues,

The LOS output from your SFP must be inverted to provide the proper SD input to the DP83822HF to indicate a link is available across fiber
-> I already doing it.

You can do this by changing bit[0] in register 0x465 to 1.
-> I tried both. (changed bit[0] in register 0x465 to 1 or 0.)
-> But, FX not working

Also, which mode are you strapping the RX_ER pin to?
-> I used RX_ER pin mode 1. It is RGMII_EN '0' and SD_DIS '0'.


Best Regards,
John

Hi Rodrigues,

I have question.

DP83822HF is not PECL.
However, most SFP modules are PECL type.

What type of module should I use?

Best Regards,
John

Hi John,

It does not matter that the 822 is a current mode line driver and that most SFPs are PECL.
This is why you have DC blocking capacitors. Please see the example diagram in the DP83822HF datasheet.
You will see that we recommend 0.1uF DC blocking caps.

Kind regards,
Ross