DP83826E: TX - Not working

Hi Marvin,

Can you please fill out the Schematic Checklist attached below? This will be a great aid in reviewing your schematic.

DP83826_Schematic_Design_Review_Checklist.xlsx

Regards,

Alvaro

Hi Alvaro,

Thank you. Here is the accomplished checklist and additional schematic for reference:

Reference and checklist.zip

I hope this helps.

Regards,

Marvin

Hi Marvin,

Thanks for the reply with the template and digital copies of the schematics.

Just a heads up, schematic reviews take at most 5 working days, I'll reach back to you by end of day Friday, August 26 at the very latest. 

Regards,

Alvaro

Hi Marvin,

Your Schematic looks good, I didn't find anything major that would contribute to the issue you're seeing.

The issue might be a layout problem, please see Section 10.2.4.1 MII Layout Guidelines in the Datasheet.

What kind of Loopbacks were you using and how were they programmed? I'm not familiar with RX Loopback. 

 Regards,

Alvaro

Hi Alvaro,

Thank you for checking.

Alvaro (Al-vuh-roe) Reyes said:

What kind of Loopbacks were you using and how were they programmed?

1) MII Loopback (setting bit[14] in the BMCR and bit[2] in BISCR) - this mode works. sending and receiving ethernet packet.
2) PCS Loopback (not sure what happens in this mode). They tried bit[0] in the BISCR and bit[1] in the BISCR - in this mode, the sent packet was not received - not work loop
3) Digital Loopback (0x0000 = 0x2100 // Disable Auto-Neg • 0x0016 = 0x0104 // Digital Loopback • 0x0122 = 0x2000 / • 0x0123 = 0x2000 • 0x0130 = 0x47FF • 0x001F = 0x4000 // Soft Reset) - in this mode nothing receive - not work loop
4) External loopback (I short 1 with 3 and 2 with 6 pins RJ-45 and use usual settings for MII mode) - in this mode nothing receive - not work loop

When TX and RX lines connected to a PC network card/router is monitored, they are able to see some ethernet packets and tring to make mass packet sending and the link led lights up.

I hope this information helps. Please let me know if you needed more information.

Regards,

Marvin

Hi Marvin,

This is a strange problem and we want to help you solve it.

Can you send a register dump with a link partner, both with successful and unsuccessful link.

Registers 0x0000-001E

And SOR1 (0x0467) & SOR2 (x0468)

This will hopefully help us find any issues.

Regards,

Alvaro

Also, is this problem common to multiple boards?

HI Alvaro,

Alvaro (Al-vuh-roe) Reyes said:

Can you send a register dump with a link partner, both with successful and unsuccessful link

I will get back to you once the customer responds.

The customer tried the PCS loopback and tried testing. Could you tell me what reasons may lead this loopback to fail?

Hi Alvaro,

The customer launched the ethernet at 10 Mbit successfully. For example, they try to use the project https://github.com/RT-Thread/realboard-lpc4088 then use 100 Mbit or auto-negotiation settings and after it reads BMCR and other registers all will be ok.

But when they try new way with PCS Loopback when checking to set 10 MFull mode and discovered that to BMCR write 0xDFFF value in this string: 

Hi Marvin,

Apologies for the long wait time, I was out on PTO last week.

The easiest way for me to resolve this would with the register dump. Could you please get this to me?

Regards,

Alvaro

Marvin,

We believe that we may be looking at the wrong thing. The register dump would help us identify the possible root cause. We can go to the loopbacks during the debug if required, but it is not a good place to start debugging. 

Regards,

Alvaro