Q-bus I/O project

[John Wilson]

This may never see the light of day (if the prototype turns out to be
stillborn) but it's pretty and I can't resist posting a pic before I've
powered it on and proven its uselessness:

	http://www.dbit.com/wilson/projects/qba.jpg

Officially it's for my morally repugnant attempts to earn a living (so it's
supposed to be a Q-bus bridge that connects over Ethernet), but I wanted to
still be able to do something fun in the very likely case that the Ethernet
port doesn't work (no idea if my PCB layout is kosher for something as fast
as the gigabit PHY's bus) or has uselessly high latency, so I added an SD
card slot and made all the CPU-end terminators switchable, so it can act
as just a plain peripheral (I'm mainly thinking disk controller -- I've
already found a reason why the USB device port can't work), if its CPU's
alive and can talk to the Q-bus.  We'll see.  Many many many chances for
mistakes.  Five different power-supply voltages, for starters.

As always, I can't say enough good things about XMOS microcontrollers and
OSHpark.com.

John Wilson
D Bit