The PSE (power sourcing equipment) tries to detect whether a device is POE or standard ethernet. Reading wikipedia it seems like this is done with a resistor. The problem is that the PSE is measuring the current at a specific voltage to read the resistance. I think the current draw of a normal power supply will change this reading. The power supply needs to be open until the PSE fully powers the lines. We could design something to do this or use an off the shelf POE part.

I hope to order prototypes any day now, but it might be a week or two. After we have tested the prototypes we will make a production run.

For the POE that is the type of part I would like to use. 500mA might not be enough power depending on what the mother board has on it. The POE spec says the voltage can go all the way to 60v (you might want some head room). Also there needs to be something for the detction process Liner has a part that does both the switching and dection, the LTC4267. The problem is that it is not as simple as the LM2597HVN-5.0-ND like you pointed out. If you come up with an elegant POE solution for the mother board we can include it in the design. Remember that the POE jack has the rectifiers built in so you have 48v DC.

What speed will it run at?

Also I was wondering how far you are from a completed device, .

As for the POE, you could use a switching regulator like this digikey part (500mA, 5V):
LM2597HVN-5.0-ND
They require a few smaller parts and three larger ones: one 68uF cap(60v) 100uf(5V) and a 100uH inductor.

Thanks for your interest. I think for a second generation we might use gschem. I’ve tried it before, but I didn’t find it as easy to use as Eagle. I used the Atmel reference design for much of the design. I changed some things like the power supply and the ethernet PHY. All of the decoupling capacitors are close to the pins, and both the power and ground nets are stars (there are no loops).

-Paul

You said your design is 2 layers? What frequency are you planning to run at? You probably know a ground/power plane is helpful for noise suppression at higher frequencies (100-200MHz). Also which docs are you using to design your board? The Atmel app notes?

I have also been looking at Power over Ethernet designs. Its too bad that the chips are on backorder at Digikey until mid august.

Anyway, awesome project. I would like to help out if possible.

-Brian