This is sort of skipping to the end, but I am going to see if I can use a 50x80 mm board for this project and the same case that I use for my GPSDO project. The big question mark is whether an RJ45 jack will fit vertically in the available space or not. Or, if not, whether a taller 50x80 extruded chassis is available.

Rather than use a 2.1mm power jack as I always have, I am leaning more towards using a USB microB jack for this project. The reason for that would be so that the same jack could be used as a firmware update port as well as to supply power. As with Orthrus, there will be an internal ERASE header that will force the chip to boot into SAM-BA to accept new firmware over USB. It may be possible to update the firmware over Ethernet as well (TBD), but this would be a fail-safe method to reclaim control of a bricked device.

The back panel will have the power and antenna jacks. I am envisioning putting the Ethernet jack on the front panel so that the integrated LEDs would be visible (and because I'm not sure there would be sufficient space on the back). I'm not yet sure about UI options on the front. I could go with just some light pipes to display rudimentary status, but for extra credit it sure would be nice to be able to actually display the time.

The hardware should wind up - again - being fairly straightforward. I intend to steal the Ethernet design directly from the E70 Xplained board. Most of the rest of the design comes over from Orthrus. The SkyTraq GPS stuff is quite mature at this point having been put to use in a number of my other projects. The only remaining design questions are the optimal wiring of the PPS signal. The intent will be to use it as a timer capture input. The datasheet is a little unclear how best to achieve that, unfortunately.