The Road to Raspberry Pi4B/ PoE Hat RoadTest Review (PoE insight needed)

RE: The Road to Raspberry Pi4B/ PoE Hat RoadTest Review (PoE insight needed)

shabaz — Fri, 08 May 2020 23:02:14 GMT

Hi Sean,

There's a reasonably high chance it could be a cable issue. Regardless of the unit being unpowered, I think at most there will be a transformer inside the L-Com unit in the path of the network connection wires, or maybe nothing at all, and so in theory the Ethernet I believe should function with it unpowered, for Pi 4 and Pi 3. You'll be unable to get Gigabit Ethernet speeds with that particular L-Com model but 100 mbps link connection should automatically work.

Are you using the long cat 6 cable? If so, it may be worth trying with ready-built shorter patch cables too, just to eliminate cable length and the connectors on the cable in case they they are intermittently functioning.

Example data connections wiring.. this not for a PoE power injector, but you can see the general idea with the transformers. This is from a DIY PoE 'powered device. The L-Com unit may or may not even have these in the path, it could be a straight wired connection from the input socket to the output socket, for two pairs of wires. In other words, either way, it is a passive circuit for the data portion, for the L-Com unit I suspect, so it wouldn't matter if it was switched on or not. All guesswork though.

I could be totally wrong, since I've never used the L-Com device.. so it's just a theory.

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RE: The Road to Raspberry Pi4B/ PoE Hat RoadTest Review (PoE insight needed)

kmikemoo — Fri, 08 May 2020 18:25:13 GMT

[mention:77de285dc3304dd5b943ccb7ee803caa:e9ed411860ed4f2ba0265705b8793d05] I cannot replicate the issue. Initially, my unpowered PoE injector didn't pass signal. Once I plugged it in and established communication through it, now it passes signal even when unplugged. The only way I could hang the system was to have the PoE and USB-C powering the Pi and ssh shutdown. Since it had two power sources, I couldn't power cycle the Pi - so it wouldn't restart. Back to work.

RE: The Road to Raspberry Pi4B/ PoE Hat RoadTest Review (PoE insight needed)

kmikemoo — Fri, 08 May 2020 14:24:54 GMT

[mention:77de285dc3304dd5b943ccb7ee803caa:e9ed411860ed4f2ba0265705b8793d05] Are you using a PoE injector as the PoE power supply? I don't understand the "on/off" in A, D, F and H. Could you clarify? Finally, is the switch PoE or unpowered? Thanks.