I'm anxiously awaiting the delivery of my second set of custom designed PCBs from BatchPCB.
The first board I designed was pretty darn simple and didn't have any problems.
This second set includes a full on arduino compatible board plus two shields for it. Somehow I suspect I made a mistake somewhere.
My question is: what sorts of things have other folks gotten wrong? When I start debugging why that board doesn't work, what kind of things should I be looking for? What are the first things that you check?
As it turns out, my boards have two problems. The first is that there's a cap too close to the ISP header. I just didn't allow enough space. The second is that the holes I specified, while large enough for all my normal through-hole components, are too small for breakaway headers to fit into without manually reaming them out a little bit (almost like it's just the thickness of the plating layer that covers the copper). Other than that, everything is good. I very carefully checked all the power connections before doing anything to make sure I wasn't about to short something badly, and held the various boards up to the light and verified alignment of stacking headers.
Best Answer
After you make sure power/ground aren't shorted, make sure that any silk screen or pin 1 markings for polarized components are correct - you don't want to go soldering that kind of stuff in backwards. After that it's really kind of random.
I was involved in bringing up a number of multi-layer boards over the years (not my designs) and we had pretty much any kind of screw-up you could make - traces that didn't go where they should, traces that simply weren't there, pads that weren't connected to their traces, etc, etc. I once even saw an issue where a broken trace was caused by the guys who built up the board gripping it wrong with pliers to break off a break-away section.
We were doing high layer-count designs, so we also had a lot of internal layer foolishness that you aren't going to see on a 2 or 4 layer board (registration can be...interesting when you've got 10 or more layers).
Once you get past the power/ground thing, you're probably not going to have too much trouble. Just take your time, test each bit of functionality one by one, and you should be good to go. If you're feeling paranoid, you could try building up the board one bit at a time (first put on and test the power, then the CPU and it's communications.
If you're feeling REALLY paranoid, you can sit down with the schematic and a meter and buzz-out the entire board. But unless the board is really small, that's gonna take a while.
You definitely want to get the main board working before you start on the secondary boards.
Good luck!