Ethernet autonegotiation with OM5P via REV POE injector takes a long but inconsistent amount of time

[e-bonner]

When we connect our Systemcore to an OM5P via a REV POE injector the time to bring up the ethernet link (after the radio finishes booting or when reconnecting the cable) is very unpredictable. It is often in the 10 to 20 second range, but sometimes takes up to a few minutes. Before it comes up, the ethernet LEDs on the Systemcore are both off but the ethernet link LED on the radio flashes briefly every 2 seconds. That is not a normal state for the radio LED, but I could not find documentation of what that LED pattern means.

The problem seems to require both the radio and the POE cable: It does not occur when connecting the Systemcore and radio directly without a POE cable or when connecting Systemcore and a USB-ethernet adapter (Realtek USB3 gigabit chipset) via a POE cable. The issue is reproducible with both radio ports. Putting a 10/100 ethernet switch between the two devices completely resolves the problem.

It seems like this issue has to do with the fact that the POE injector only has the two pairs needed for 10/100 connected but the devices on both ends of the connection support gigabit. However, that doesn't really explain why the connection would work only after a random long amount of time; I would expect the behavior to be consistent even if it did not work properly.

[ThadHouse]

I wouldn't be surprised if this is a similar root cause to #198

I suspect its worse when both devices try to autonegotiate gigabit, and wouldn't be surprised if the interaction gets even weirder.