[gta02-core] more reviews

[Werner Almesberger]

?lvaro Lopes wrote:
> I wonder why schematics show it as a 4-pin device.

Maybe it was a four-pin package earlier and was replaced later
on, or maybe someone just copied the symbol over from X1501
and changed the pin numbers.

While we're making changes to the crystals, how about giving
them a slightly more generic ? There are lots of tuning fork or
4-pad packages around that could all use the same symbol.

One possible naming scheme would be XTAL_x_y with x being the
number of pins/pads and y being the pair of pins/pads that
connect to the actual crystal.

So X1501 would be XTAL_4_13 and X1701 would be XTAL_3_12.
Leafing through the Digi-Key catalog, here are some more
examples:

- ECS-35-17-28A would be XTAL_4_14
  http://www.ecsxtal.com/store/pdf/csm-4a.pdf

- ECS-35-17-18 could be XTAL_4_1234 (if we map the pad names
  A -> 1, B -> 2, etc.)
  http://www.ecsxtal.com/store/pdf/csm-12r.pdf

- Werner