we designed a Ethernet board with a Intel I210-IS controller and connected them to a SFP cage.
The I210 controller works fine after programming but we faced a problem.
If the a fiber optic cable is connected to the assembled SFP module and we switch on our system the link to the I210 controller is lost. The I210 controller don't work anymore and is also not available under OS (Linux Ubuntu).
If we don't connect a cable but with SFP module and we switch on our system and connect the cable later everything works fine without problems.
The difference between our schematic and the reference design are the SDP pins.
We didn't used them. The power for the SFP module is controlled by our system PSU and not by the I210 chip via P-channel MOSFET connected to SDP3.
Also the other SDP signals are not connected to the MOD_ABS, TX_DISABLE nor TX_FAULT.
The SDP pins have no external hardware e.g. pull-ups or pull-down resistors.
We are not sure if a MOSFET will solve our problem.
We found out that if we pull-down the SIG_DET signal and power up the system we have the same result as with the cable.
We removed the SIG_DET signal on our board and pull-down the signal with a 1k resistor to see if we have the same result as with a plugged cable. The I210 works fine. But if we have again a plugged cable to the interface and the 1k pull-down but with no connection between the LOS signal from SFP module and I210 SIG_DET signal we have the same bad result.
Has anyone an idea what could be the problem here?
Thank you for posting in Intel Ethernet Communities.
Base on your inquiry, we have specific forum for these issues and I will be transferring this thread for faster response.
Please wait for their reply within 1 to 2 business days.
Thank you and stay safe.
Intel® Customer Support Technician
Thank you for contacting Intel Embedded Community.
Based on your previous communication, could you please clarify if this situation happens only with the mentioned Operating System (OS)?
Could you please list the sources that you used to implement the affected design?
We are waiting for your answer to these questions.
Hello @CarlosAM_INTEL ,
thank you for your answer to my request.
It looks like that the OS is not the problem. The link failed before the OS starts.
In the mean time we found out that with another SFP module our board works fine and we shipped the board now to our customer.
Maybe it's only a problem from the Avago SFP module which we used.
For our comprehension, is the FET for the power from the module really needed?
As I measured with an Osci, the SDP3 goes low after the start, module is powered, after 17s, the signal goes to high, module off, and after
some seconds the signal switched back to low and stay on low, module on.
We are very limited with the signals on our board connector and if the SDP signals are not really needed for the function it would help us a lot.
the FET is a part of the refernence design, see attached a screenshot with the marked FET.
We don't have this FET in our design and also the other SDP signals are not connected.
Are they needed for the controller function?