DP83640: DP83640 MDIO question

Cheng Chen4

Part Number: DP83640
Other Parts Discussed in Thread: TMS320F28388D, DP83826EVM, USB-2-MDIO

Hi,

I have a question about connecting MII interface. Can I program the MDIO CLK and MDIO DATA through usb cable while other pins are still connected through mac layer on MCU?

The reason I asked is I found TMS320F28388D MCU does not provide MDIO output and I want to replace the PHY transceiver to DP83640. Thanks

Regards,

Cheng

over 5 years ago

0 Nikhil Menon over 5 years ago

TI__Genius 11725 points

Hi Cheng,

We are looking into your question and will provide feedback by Thursday this week.

Thank you,

Nikhil

0 Nikhil Menon over 5 years ago in reply to Nikhil Menon

TI__Genius 11725 points

Hi Cheng,

In regards to your question

"Can I program the MDIO CLK and MDIO DATA through usb cable while other pins are still connected through mac layer on MCU?"

Yes this can be done so-long as all connected devices use the same IO voltage.

Thank you,

Nikhil

0 Cheng Chen4 over 5 years ago in reply to Nikhil Menon

Intellectual 270 points

Hi NIkhil,

Thanks for the reply. I have one MCU which does not have MDIO pin output. A possible solution I can think of is connecting MDIO pins to computer through USB to computer. Meanwhile, the rest of MII pins are still connected to MCU and MCU to computer. So do you mean this is not a solution? Thanks.

Regards,

Cheng

0 Nikhil Menon over 5 years ago in reply to Cheng Chen4

TI__Genius 11725 points

Hi Cheng,

Do you mean you are connecting the MDIO/MDC pins directly to a PC through USB connection? Can you provide a schematic or a connection diagram?

Thank you,

Nikhil

0 Cheng Chen4 over 5 years ago in reply to Nikhil Menon

Intellectual 270 points

Hi Nikhil,

Yes. That is exactly what I meant. Just to be clear, I attached a rough sketch. Thanks.

Regards,

Cheng

0 Nikhil Menon over 5 years ago in reply to Cheng Chen4

TI__Genius 11725 points

Hi Cheng,

From what I understand, USB uses differential signaling at a 5V level. How are MDIO/MDC routed to the laptop via the USB signals? Can you show the pin/trace connections? Have you tested this method before?

Thank you,

Nikhil

0 Cheng Chen4 over 5 years ago in reply to Nikhil Menon

Intellectual 270 points

I am not sure How MDIO/MDC routed to the laptop. I am using mini-USB port (J7) for USB connection. After connecting to laptop, I am using Analog LauchPad to control its registers. I didn't try it before and I was trying to figure out its feasibility.

Regards,

Cheng

0 Nikhil Menon over 5 years ago in reply to Cheng Chen4

TI__Genius 11725 points

Hi Cheng,

We are looking into this issue and will provide feedback by Wednesday this week.

Thank you,

Nikhil

0 Nikhil Menon over 5 years ago in reply to Nikhil Menon

TI__Genius 11725 points

Hi Cheng,

As long as the voltage and timing requirements of the MDIO/MDC signals are met, this should be ok. The voltage levels of the MDIO/MDC signals should be in the same domain as the VDDIO level of the PHY.

Thank you,

Nikhil

0 Cheng Chen4 over 5 years ago in reply to Nikhil Menon

Intellectual 270 points

Hi Nikhil,

Thanks for the information. What do you mean by same domain? Does that mean something other than the same voltage source? So for the setup I described, does that fit the requirement? Thanks.

Regards,
Cheng

0 Nikhil Menon over 5 years ago in reply to Cheng Chen4

TI__Genius 11725 points

Hi Cheng,

By same domain, I simply mean the same voltage level. If VDDIO of the PHY is 3.3 V, the voltage level used for MDIO/MDC signaling should be 3.3V.

We have not tested this setup of directly connecting MDC/MDIO to laptop via USB has not been tested so we cannot guarantee performance. Typically for register control on bench, we control the PHY with a device such as an MSP430 launchpad in-between the PHY and the laptop. You may view the DP83826EVM User Guide and Schematics for an example of this.

We use our USB-2-MDIO tool to communicate with the PHYs through the MSP.

I hope this helps.

Thank you,

Nikhil

0 Cheng Chen4 over 5 years ago in reply to Nikhil Menon

Intellectual 270 points

Hi Nikhil,

That's great help! Thanks a lot!

Regards,

Cheng

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DP83640: DP83640 MDIO question