Add n|fuse PoE HAT with Mini PCIe and M.2 Slot Options

[geerlingguy]

n|fuse has a Power over Ethernet Hat for the Raspberry Pi 5 with mini PCIe and M.2 Slot options, which combines a PoE HAT capable of 25W of power, plus a mini PCIe, M.2 M-key, or M.2 E-key slot, in a low profile board that should fit inside standard Pi 5 cases.

Could be nice for deploying edge Pis with PoE instead of separate power + networking, without needing two HATs or a separate PoE power adapter and multiple cables running to the Pi.

[geerlingguy]

I have one of these on hand to test!

[geerlingguy]

On the site here: https://pipci.jeffgeerling.com/hats/n-fuse-poe-hat-pcie.html

[geerlingguy]

In looking over the unit I was sent, I noticed a few things and have sent an email to n|fuse to ask about them:

• There is no isolation transformer, which IIRC is a requirement for any PoE PD (Powered Device), to provide protection from overvoltage (and maybe other benefits?). But maybe they have some other protection in place?
• My unit didn't include a PCIe FFC, or a GPIO passthrough header, so I needed to supply my own — hopefully production units will include those.
• The board is almost compatible with the Pi Active Cooler, but it looks like three heatsink fins would need to be snipped to make it fit. I have asked what cooling solution is recommended with this board.

I'm going to wait for further testing until I hear back from n|fuse.

[geerlingguy]

Some responses:

• n|fused modified Active Coolers using a similar technique that I used for the Radxa Penta SATA HAT — physically removing three of the heatsink fins (I used a needle-nose pliers)
• They will ship a set of screws, standoffs, and cables with their units (my test unit was just not shipped with them as it was early production)
• Regarding the lack of a transformer: "That's true, the design is not isolated. The advantage of our design is certainly that is supports PoE .bt and is pretty efficient."

More test notes:

• Thermals were interesting (see later image). This huge inductor got up to 60°C, and what's weirder is the edge of the board where there are just some status LEDs was getting past 50°C. I wonder if there's some extra current running through there or something, not sure.
• Coil whine: Couldn't hear anything at all, possibly partly from lack of transformer?
• Installed, a couple of the circuits bump against the Active Cooler fan
• Shutdown worked fine, and you can still see PoE Power status and type indicator LEDs while the Pi is powered off

I have a question in regarding what the LEDs mean, and if the heat in that corner of the board is expected behavior.