Just a recap of the Keg boot sequence described in PN forums by Ryan.
http://www.phatnoise.com/forum/showthread.php?s=&threadid=2362"Standard PhatBox Operation:
When it first gets power, it boots of off protected non-HU specific firmware (that never gets reprogrammed) and then turns off if there is no firmware update on the DMS (this prevents it from becoming a doorstop if it gets programmed with bad firmware).
After it turns off, it is running HU specific firmware and should be talking to the HU. When it gets ignition, it will boot the Linux processor.
The red light shows power to the Linux processor. The green light shows HDD activity and custom status "messages".
If the lights don't come on at all with ignition, that simply means that the microcontroller is not getting the ignition signal. In this case it is a bad cable or a bad connection. Make sure the hex screws are all the way in before screwing the cable into the PhatBox (or the cable could possibly be connecting power, but not ignition)."
