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How to adapt SFP modul with Cortex-M microcontroller?

Samuel Ölke
Prodigy 200 points

Hello everyone,

I need some ideas and recommendations on how to solve the following problem effectively.

Our customer wants to use SFP modules (1000 Base-SX standard) to send some data to a remote computer. As there is only very little data to be transferred (actually no real need for gigabit), a Cortex-M microcontroller would probably do the job.

What would be the best approach to adapt the fiber optical SFP modul? From what I've found, most microcontrollers only have a MII or RMII interface. The only information I've found on the SFP modules is from the following document: SFP modules. What PHY would you recommend for this project?

How would the design change, if we want to add a copper interface as well? Copper and fiber would never be active at the same time. What PHY would you recommend then?

Your help is very much appreciated.

Thanks a lot.

 

Best regards,
Samuel

  • 0
    TI__Guru**** 177546 points

    Hi,

      Sorry, we don't have a Cortex-M processor that support GigaBit Ethernet. 

  • 0 in reply to Charles Tsai
    Prodigy 200 points

    Hello,

    thanks for your reply. I think my main problem is indeed the selection of a suitable PHY.

    Let's say I want to use a microcontroller that comes with a 10/100 MAC interface.
    On the other end, I have SFP moduls, either copper or fiber, 1000 Base-SX or 1000 Base-T.

    I've checked some datasheets of SFP modules and they all seem to have the same interface, although, many SFP modules are described as "brand xy" compliant. Does this mean there are hardware or software differences depending on the brand?

    From what I understand, for our application a PHY has to be capabable of handling copper and fiber SFPs. Not all PHYs explicitly state they are. So apparently, there has to be a difference by used media?

    And last but not least, there is the speed compatibility. Ethernet should be backwards compatible, but I'm not sure a 1000 Base-T or 1000 Base-X SFP is actually capable of handling slower speeds. And if the SFP is, can it actually be connected to a 10/100 STM32 MAC?

    Seriously, these SFPs are so confusing. I havn't found any examples or similar projects online. I'm currently doubting this whole approach makes sense. But what other options are there? Building our own transceivers doesn't make sense either.

    Best regards,
    Samuel

  • 0 in reply to Samuel Ölke
    TI__Guru**** 177546 points

    Hi,

     TM4C129 MCUs are Cortex-M based and they come with an integrated PHY on the chip. I have no understanding of SFP module. Can SFP utilize the integrated PHY which supports 10Base-T and 100Base-TX signaling. There are some variants of TM4C129 family that have MII/RMII. If you are looking for a specific PHY that can work with your SFP module then I can't comment. My knowledge is limited to MCU only. Please also note that TM4C129 MAC are compliant to 10BASE-T/100BASE-TX IEEE-802.3. It does not support Gigabit transmission.